@article{yu_koenig_lee_2023, title={Charged-Particle Bound States in Periodic Boxes}, volume={131}, ISSN={["1079-7114"]}, url={https://doi.org/10.1103/PhysRevLett.131.212502}, DOI={10.1103/PhysRevLett.131.212502}, abstractNote={We consider the binding energy of a two-body system with a repulsive Coulomb interaction in a finite periodic volume. We define the finite-volume Coulomb potential as the usual Coulomb potential, except that the distance is defined as the shortest separation between the two bodies in the periodic volume. We investigate this problem in one and three-dimensional periodic boxes and derive the asymptotic behavior of the volume dependence for bound states with zero angular momentum in terms of Whittaker functions. We benchmark our results against numerical calculations and show how the method can be used to extract asymptotic normalization coefficients for charged-particle bound states. The results we derive here have immediate applications for calculations of atomic nuclei in finite periodic volumes for the case where the leading finite-volume correction is associated with two charged clusters.}, number={21}, journal={PHYSICAL REVIEW LETTERS}, author={Yu, Hang and Koenig, Sebastian and Lee, Dean}, year={2023}, month={Nov} }
 @article{li_elhatisari_epelbaum_lee_lu_meissner_2019, title={Galilean invariance restoration on the lattice}, volume={99}, ISSN={["2469-9993"]}, DOI={10.1103/PhysRevC.99.064001}, abstractNote={We consider the breaking of Galilean invariance due to different lattice cutoff effects in moving frames and a nonlocal smearing parameter which is used in the construction of the nuclear lattice interaction. The dispersion relation and neutron-proton scattering phase shifts are used to investigate the Galilean invariance breaking effects and ways to restore it. For $S$-wave channels, ${}^1S_0$ and ${}^3S_1$, we present the neutron-proton scattering phase shifts in moving frames calculated using both L\"uscher's formula and the spherical wall method, as well as the dispersion relation. For the $P$ and $D$ waves, we present the neutron-proton scattering phase shifts in moving frames calculated using the spherical wall method. We find that the Galilean invariance breaking effects stemming from the lattice artifacts partially cancel those caused by the nonlocal smearing parameter. Due to this cancellation, the Galilean invariance breaking effect is small, and the Galilean invariance can be restored by introducing Galilean invariance restoration operators.}, number={6}, journal={PHYSICAL REVIEW C}, author={Li, Ning and Elhatisari, Serdar and Epelbaum, Evgeny and Lee, Dean and Lu, Bingnan and Meissner, Ulf-G}, year={2019}, month={Jun} }
 @article{klein_lee_meissner_2018, title={Lattice improvement in lattice effective field theory}, volume={54}, ISSN={["1434-601X"]}, DOI={10.1140/epja/i2018-12676-1}, abstractNote={Lattice calculations using the framework of effective field theory have been applied to a wide range of few-body and many-body systems. One of the challenges of these calculations is to remove systematic errors arising from the nonzero lattice spacing. Fortunately, the lattice improvement program pioneered by Symanzik provides a formalism for doing this. While lattice improvement has already been utilized in lattice effective field theory calculations, the effectiveness of the improvement program has not been systematically benchmarked. In this work we use lattice improvement to remove lattice errors for a one-dimensional system of bosons with zero-range interactions. We construct the improved lattice action up to next-to-next-to-leading order and verify that the remaining errors scale as the fourth power of the lattice spacing for observables involving as many as five particles. Our results provide a guide for increasing the accuracy of future calculations in lattice effective field theory with improved lattice actions.}, number={12}, journal={EUROPEAN PHYSICAL JOURNAL A}, author={Klein, Nico and Lee, Dean and Meissner, Ulf-G.}, year={2018}, month={Dec} }
 @article{freer_horiuchi_kanada-en'yo_lee_meissner_2018, title={Microscopic clustering in light nuclei}, volume={90}, ISSN={["1539-0756"]}, DOI={10.1103/RevModPhys.90.035004}, abstractNote={We review recent experimental and theoretical progress in understanding the microscopic details of clustering in light nuclei. We discuss recent experimental results on $\alpha$-conjugate systems, molecular structures in neutron-rich nuclei, and constraints for ab initio theory. We then examine nuclear clustering in a wide range of theoretical methods, including the resonating group and generator coordinate methods, antisymmetrized molecular dynamics, Tohsaki-Horiuchi-Schuck-R\"opke wave function and container model, no-core shell model methods, continuum quantum Monte Carlo, and lattice effective field theory.}, number={3}, journal={REVIEWS OF MODERN PHYSICS}, author={Freer, Martin and Horiuchi, Hisashi and Kanada-En'yo, Yoshiko and Lee, Dean and Meissner, Ulf-G.}, year={2018}, month={Aug} }
 @article{li_elhatisari_epelbaum_lee_lu_meissner_2018, title={Neutron-proton scattering with lattice chiral effective field theory at next-to-next-to-next-to-leading order}, volume={98}, ISSN={["2469-9993"]}, DOI={10.1103/PhysRevC.98.044002}, abstractNote={We present a new lattice formulation of chiral effective field theory interactions with a simpler decomposition into spin channels. With these interactions the process of fitting to the empirical scattering phase shifts is simplified, and the resulting lattice phase shifts are more accurate than in previous studies. We present results for the neutron-proton system up to next-to-next-to-next-to-leading order for lattice spacings of $1.97~{\rm fm}$, $1.64~{\rm fm}$, $1.32~{\rm fm}$, and $0.99~{\rm fm}$. Our results provide a pathway to $\textit{ab initio}$ lattice calculations of nuclear structure, reactions, and thermodynamics with accurate and systematic control over the chiral nucleon-nucleon force.}, number={4}, journal={PHYSICAL REVIEW C}, author={Li, Ning and Elhatisari, Serdar and Epelbaum, Evgeny and Lee, Dean and Lu, Bing-Nan and Meissner, Ulf-G}, year={2018}, month={Oct} }
 @article{klein_elhatisari_laehde_lee_meissner_2018, title={The Tjon band in Nuclear Lattice Effective Field Theory}, volume={54}, ISSN={["1434-601X"]}, DOI={10.1140/epja/i2018-12553-y}, abstractNote={We explore the lattice spacing dependence in Nuclear Lattice Effective Field Theory for few-body systems up to next-to-next-to leading order in chiral effective field theory including all isospin breaking and electromagnetic effects, the complete two-pion-exchange potential, and the three-nucleon forces. We calculate phase shifts in the neutron-proton system and proton-proton systems as well as the scattering length in the neutron-neutron system. We then perform a full next-to-next-to-leading order calculation with two-nucleon and three-nucleon forces for the triton and helium-4, and analyse their binding energy correlation. We show how the Tjon band is reached by decreasing the lattice spacing, and confirm the continuum observation that a four-body force is not necessary to describe light nuclei.}, number={7}, journal={EUROPEAN PHYSICAL JOURNAL A}, author={Klein, Nico and Elhatisari, Serdar and Laehde, Timo A. and Lee, Dean and Meissner, Ulf-G.}, year={2018}, month={Jul} }
 @article{koenig_lee_2018, title={Volume dependence of N-body bound states}, volume={779}, ISSN={["1873-2445"]}, DOI={10.1016/j.physletb.2018.01.060}, abstractNote={We derive the finite-volume correction to the binding energy of an N-particle quantum bound state in a cubic periodic volume. Our results are applicable to bound states with arbitrary composition and total angular momentum, and in any number of spatial dimensions. The only assumptions are that the interactions have finite range. The finite-volume correction is a sum of contributions from all possible breakup channels. In the case where the separation is into two bound clusters, our result gives the leading volume dependence up to exponentially small corrections. If the separation is into three or more clusters, there is a power-law factor that is beyond the scope of this work, however our result again determines the leading exponential dependence. We also present two independent methods that use finite-volume data to determine asymptotic normalization coefficients. The coefficients are useful to determine low-energy capture reactions into weakly bound states relevant for nuclear astrophysics. Using the techniques introduced here, one can even extract the infinite-volume energy limit using data from a single-volume calculation. The derived relations are tested using several exactly solvable systems and numerical examples. We anticipate immediate applications to lattice calculations of hadronic, nuclear, and cold atomic systems.}, journal={PHYSICS LETTERS B}, publisher={Elsevier BV}, author={Koenig, Sebastian and Lee, Dean}, year={2018}, month={Apr}, pages={9–15} }
 @article{elhatisari_epelbaum_krebs_lahde_lee_li_lu_meissner_rupak_2017, title={Ab initio calculations of the isotopic dependence of nuclear clustering}, volume={119}, DOI={10.1103/physrevlett.119.222505}, abstractNote={Nuclear clustering describes the appearance of structures resembling smaller nuclei such as alpha particles (^{4}He nuclei) within the interior of a larger nucleus. In this Letter, we present lattice Monte Carlo calculations based on chiral effective field theory for the ground states of helium, beryllium, carbon, and oxygen isotopes. By computing model-independent measures that probe three- and four-nucleon correlations at short distances, we determine the shape of the alpha clusters and the entanglement of nucleons comprising each alpha cluster with the outside medium. We also introduce a new computational approach called the pinhole algorithm, which solves a long-standing deficiency of auxiliary-field Monte Carlo simulations in computing density correlations relative to the center of mass. We use the pinhole algorithm to determine the proton and neutron density distributions and the geometry of cluster correlations in ^{12}C, ^{14}C, and ^{16}C. The structural similarities among the carbon isotopes suggest that ^{14}C and ^{16}C have excitations analogous to the well-known Hoyle state resonance in ^{12}C.}, number={22}, journal={Physical Review Letters}, author={Elhatisari, S. and Epelbaum, E. and Krebs, H. and Lahde, T. A. and Lee, D. and Li, N. and Lu, B. N. and Meissner, U. G. and Rupak, G.}, year={2017} }
 @article{rokash_epelbaum_krebs_lee_2017, title={Effective Forces Between Quantum Bound States}, volume={118}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.118.232502}, abstractNote={Recent ab initio lattice studies have found that the interactions between alpha particles (^{4}He nuclei) are sensitive to seemingly minor details of the nucleon-nucleon force, such as interaction locality. In order to uncover the essential physics of this puzzling phenomenon without unnecessary complications, we study a simple model involving two-component fermions in one spatial dimension. We probe the interaction between two bound dimers for several different particle-particle interactions and measure an effective potential between the dimers using external point potentials which act as numerical tweezers. We find that the strength and range of the local part of the particle-particle interactions play a dominant role in shaping the interactions between the dimers and can even determine the overall sign of the effective potential.}, number={23}, journal={PHYSICAL REVIEW LETTERS}, author={Rokash, Alexander and Epelbaum, Evgeny and Krebs, Hermann and Lee, Dean}, year={2017}, month={Jun} }
 @article{alarcon_du_klein_laehde_lee_li_lu_luu_meissner_2017, title={Neutron-proton scattering at next-to-next-to-leading order in Nuclear Lattice Effective Field Theory}, volume={53}, ISSN={["1434-601X"]}, DOI={10.1140/epja/i2017-12273-x}, abstractNote={We present a systematic study of neutron-proton scattering in Nuclear Lattice Effective Field Theory (NLEFT), in terms of the computationally efficient radial Hamiltonian method. Our leading-order (LO) interaction consists of smeared, local contact terms and static one-pion exchange. We show results for a fully non-perturbative analysis up to next-to-next-to-leading order (NNLO), followed by a perturbative treatment of contributions beyond LO. The latter analysis anticipates practical Monte Carlo simulations of heavier nuclei. We explore how our results depend on the lattice spacing a, and estimate sources of uncertainty in the determination of the low-energy constants of the next-to-leading-order (NLO) two-nucleon force. We give results for lattice spacings ranging from a = 1.97 fm down to a = 0.98 fm, and discuss the effects of lattice artifacts on the scattering observables. At a = 0.98 fm, lattice artifacts appear small, and our NNLO results agree well with the Nijmegen partial-wave analysis for S -wave and P-wave channels. We expect the peripheral partial waves to be equally well described once the lattice momenta in the pion-nucleon coupling are taken to coincide with the continuum dispersion relation, and higher-order (N3LO) contributions are included. We stress that for center-of-mass momenta below 100MeV, the physics of the two-nucleon system is independent of the lattice spacing.}, number={5}, journal={EUROPEAN PHYSICAL JOURNAL A}, author={Alarcon, Jose Manuel and Du, Dechuan and Klein, Nico and Laehde, Timo A. and Lee, Dean and Li, Ning and Lu, Bing-Nan and Luu, Thomas and Meissner, Ulf-G.}, year={2017}, month={May} }
 @article{elhatisari_katterjohn_lee_meissner_rupak_2017, title={Universal dimer-dimer scattering in lattice effective field theory}, volume={768}, ISSN={["1873-2445"]}, DOI={10.1016/j.physletb.2017.03.011}, abstractNote={We consider two-component fermions with short-range interactions and large scattering length. This system has universal properties that are realized in several different fields of physics. In the limit of large fermion–fermion scattering length aff and zero-range interaction, all properties of the system scale proportionally with aff. For the case with shallow bound dimers, we calculate the dimer–dimer scattering phase shifts using lattice effective field theory. We extract the universal dimer–dimer scattering length add/aff=0.618(30) and effective range rdd/aff=−0.431(48). This result for the effective range is the first calculation with quantified and controlled systematic errors. We also benchmark our methods by computing the fermion–dimer scattering parameters and testing some predictions of conformal scaling of irrelevant operators near the unitarity limit.}, journal={PHYSICS LETTERS B}, author={Elhatisari, Serdar and Katterjohn, Kris and Lee, Dean and Meissner, Ulf-G. and Rupak, Gautam}, year={2017}, month={May}, pages={337–344} }
 @article{elhatisari_li_rokash_alarcon_du_klein_lu_meissner_epelbaum_krebs_et al._2016, title={Nuclear Binding Near a Quantum Phase Transition}, volume={117}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.117.132501}, abstractNote={How do protons and neutrons bind to form nuclei? This is the central question of ab initio nuclear structure theory. While the answer may seem as simple as the fact that nuclear forces are attractive, the full story is more complex and interesting. In this work we present numerical evidence from ab initio lattice simulations showing that nature is near a quantum phase transition, a zero-temperature transition driven by quantum fluctuations. Using lattice effective field theory, we perform Monte Carlo simulations for systems with up to twenty nucleons. For even and equal numbers of protons and neutrons, we discover a first-order transition at zero temperature from a Bose-condensed gas of alpha particles (^{4}He nuclei) to a nuclear liquid. Whether one has an alpha-particle gas or nuclear liquid is determined by the strength of the alpha-alpha interactions, and we show that the alpha-alpha interactions depend on the strength and locality of the nucleon-nucleon interactions. This insight should be useful in improving calculations of nuclear structure and important astrophysical reactions involving alpha capture on nuclei. Our findings also provide a tool to probe the structure of alpha cluster states such as the Hoyle state responsible for the production of carbon in red giant stars and point to a connection between nuclear states and the universal physics of bosons at large scattering length.}, number={13}, journal={PHYSICAL REVIEW LETTERS}, author={Elhatisari, Serdar and Li, Ning and Rokash, Alexander and Alarcon, Jose Manuel and Du, Dechuan and Klein, Nico and Lu, Bing-nan and Meissner, Ulf-G. and Epelbaum, Evgeny and Krebs, Hermann and et al.}, year={2016}, month={Sep} }
 @article{lee_2016, title={Nuclear lattice simulations and SU(4) symmetry}, volume={25}, number={5}, journal={International Journal of Modern Physics. E, Nuclear Physics}, author={Lee, D.}, year={2016} }
 @article{elhatisari_lee_meissner_rupak_2016, title={Nucleon-deuteron scattering using the adiabatic projection method}, volume={52}, ISSN={["1434-601X"]}, DOI={10.1140/epja/i2016-16174-2}, abstractNote={In this paper we discuss the adiabatic projection method, a general framework for scattering and reaction calculations on the lattice. We also introduce several new techniques developed to study nucleus-nucleus scattering and reactions on the lattice. We present technical details of the method for large-scale problems. To estimate the systematic errors of the calculations we consider simple two-particle scattering on the lattice. Then we benchmark the accuracy and efficiency of the numerical methods by applying these to calculate fermion-dimer scattering in lattice effective field theory with and without a long-range Coulomb potential. The fermion-dimer calculations correspond to neutron-deuteron and proton-deuteron scattering in the spin-quartet channel at leading order in the pionless effective field theory.}, number={6}, journal={EUROPEAN PHYSICAL JOURNAL A}, author={Elhatisari, Serdar and Lee, Dean and Meissner, Ulf-G. and Rupak, Gautam}, year={2016}, month={Jun} }
 @article{lu_laehde_lee_meissner_2016, title={Precise determination of lattice phase shifts and mixing angles}, volume={760}, ISSN={["1873-2445"]}, DOI={10.1016/j.physletb.2016.06.081}, abstractNote={We introduce a general and accurate method for determining lattice phase shifts and mixing angles, which is applicable to arbitrary, non-cubic lattices. Our method combines angular momentum projection, spherical wall boundaries and an adjustable auxiliary potential. This allows us to construct radial lattice wave functions and to determine phase shifts at arbitrary energies. For coupled partial waves, we use a complex-valued auxiliary potential that breaks time-reversal invariance. We benchmark our method using a system of two spin-1/2 particles interacting through a finite-range potential with a strong tensor component. We are able to extract phase shifts and mixing angles for all angular momenta and energies, with precision greater than that of extant methods. We discuss a wide range of applications from nuclear lattice simulations to optical lattice experiments.}, journal={PHYSICS LETTERS B}, author={Lu, Bing-Nan and Laehde, Timo A. and Lee, Dean and Meissner, Ulf-G.}, year={2016}, month={Sep}, pages={309–313} }
 @article{bour_lee_hammer_meissner_2015, title={Ab initio Lattice Results for Fermi Polarons in Two Dimensions}, volume={115}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.115.185301}, abstractNote={We investigate the attractive Fermi polaron problem in two dimensions using nonperturbative Monte Carlo simulations. We introduce a new Monte Carlo algorithm called the impurity lattice Monte Carlo method. This algorithm samples the path integral in a computationally efficient manner and has only small sign oscillations for systems with a single impurity. As a benchmark of the method, we calculate the universal polaron energy in three dimensions in the scale-invariant unitarity limit and find agreement with published results. We then present the first fully nonperturbative calculations of the polaron energy in two dimensions and density correlations between the impurity and majority particles in the limit of zero-range interactions. We find evidence for a smooth crossover transition from fermionic quasiparticle to molecular state as a function of the interaction strength.}, number={18}, journal={PHYSICAL REVIEW LETTERS}, author={Bour, Shahin and Lee, Dean and Hammer, H. -W. and Meissner, Ulf-G.}, year={2015}, month={Oct} }
 @article{elhatisari_lee_rupak_epelbaum_krebs_lahde_luu_meissner_2015, title={Ab initio alpha-alpha scattering}, volume={528}, number={7580}, journal={Nature}, author={Elhatisari, S. and Lee, D. and Rupak, G. and Epelbaum, E. and Krebs, H. and Lahde, T. A. and Luu, T. and Meissner, U. G.}, year={2015}, pages={111-} }
 @article{lu_laehde_lee_meissner_2015, title={Breaking and restoration of rotational symmetry for irreducible tensor operators on the lattice}, volume={92}, ISSN={["1550-2368"]}, DOI={10.1103/physrevd.92.014506}, abstractNote={We study the breaking of rotational symmetry on the lattice for irreducible tensor operators and practical methods for suppressing this breaking. We illustrate the features of the general problem using an α cluster model for 8 Be. We focus on the lowest states with non-zero angular momentum and examine the matrix elements of multipole moment operators. We show that the physical reduced matrix element is well reproduced by averaging over all possible orientations of the quantum state, and this is expressed as a sum of matrix elements weighted by the corresponding Clebsch-Gordan coefficients . For our α cluster model we find that the effects of rotational symmetry breaking can be largely eliminated for lattice spacings of a≤ 1.7 fm, and we expect similar improvement for actual lattice Monte Carlo calculations.}, number={1}, journal={PHYSICAL REVIEW D}, author={Lu, Bing-Nan and Laehde, Timo A. and Lee, Dean and Meissner, Ulf-G.}, year={2015}, month={Jul} }
 @article{rokash_pine_elhatisari_lee_epelbaum_krebs_2015, title={Scattering cluster wave functions on the lattice using the adiabatic projection method}, volume={92}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.92.054612}, abstractNote={The adiabatic projection method is a general framework for obtaining a low-energy effective Hamiltonian for clusters. Previous studies have used the adiabatic projection method in combination with the finite-volume energy Luscher’s method to extract scattering phase shifts. We discuss several methods to calculate elastic phase shifts directly from asymptotic cluster wave functions obtained from the effective cluster Hamiltonian for examples in one and three dimensions. This approach is less sensitive than the finite-volume energy Luscher method to stochastic and systematic errors which appear in the application of the adiabatic projection method.}, number={5}, journal={PHYSICAL REVIEW C}, author={Rokash, Alexander and Pine, Michelle and Elhatisari, Serdar and Lee, Dean and Epelbaum, Evgeny and Krebs, Hermann}, year={2015}, month={Nov} }
 @article{lahde_epelbaum_krebs_lee_meissner_rupak_2015, title={Uncertainties of Euclidean time extrapolation in lattice effective field theory}, volume={42}, number={3}, journal={Journal of Physics. G, Nuclear and Particle Physics}, author={Lahde, T. A. and Epelbaum, E. and Krebs, H. and Lee, D. and Meissner, U. G. and Rupak, G.}, year={2015} }
 @article{epelbaum_krebs_laehde_lee_meissner_rupak_2014, title={Ab Initio Calculation of the Spectrum and Structure of O-16}, volume={112}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.112.102501}, abstractNote={We present ab initio lattice calculations of the low-energy even-parity states of 16O using chiral nuclear effective field theory. We find good agreement with the empirical energy spectrum, and with the electromagnetic properties and transition rates. For the ground state, we find that the nucleons are arranged in a tetrahedral configuration of alpha clusters. For the first excited spin-0 state, we find that the predominant structure is a square configuration of alpha clusters, with rotational excitations that include the first spin-2 state.}, number={10}, journal={PHYSICAL REVIEW LETTERS}, author={Epelbaum, Evgeny and Krebs, Hermann and Laehde, Timo A. and Lee, Dean and Meissner, Ulf-G. and Rupak, Gautam}, year={2014}, month={Mar} }
 @inproceedings{lee_2014, title={Ab initio nuclear structure from lattice effective field theory}, volume={1625}, booktitle={Xxxvi brazilian workshop on nuclear physics}, author={Lee, D.}, year={2014}, pages={3–9} }
 @article{lu_laehde_lee_meissner_2014, title={Breaking and restoration of rotational symmetry on the lattice for bound state multiplets}, volume={90}, ISSN={["1550-2368"]}, DOI={10.1103/physrevd.90.034507}, abstractNote={We explore the breaking of rotational symmetry on the lattice for bound state energies and practical methods for suppressing this breaking. We demonstrate the general problems associated with lattice discretization errors and finite-volume errors using an $\alpha$ cluster model for $^8$Be and $^{12}$C. We consider the two and three $\alpha$-particle systems and focus on the lowest states with non-zero angular momentum which split into multiplets corresponding to different irreducible representations of the cubic group. We examine the dependence of such splittings on the lattice spacing and box size. We find that lattice spacing errors are closely related to the commensurability of the lattice with the intrinsic length scales of the system. We also show that rotational symmetry breaking effects can be significantly reduced by using improved lattice actions, and that the physical energy levels are accurately reproduced by the weighted average of a given spin multiplets.}, number={3}, journal={PHYSICAL REVIEW D}, author={Lu, Bing-Nan and Laehde, Timo A. and Lee, Dean and Meissner, Ulf-G.}, year={2014}, month={Aug} }
 @article{elhatisari_lee_2014, title={Fermion-dimer scattering using an impurity lattice Monte Carlo approach and the adiabatic projection method}, volume={90}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.90.064001}, abstractNote={We present lattice Monte Carlo calculations of fermion-dimer scattering in the limit of zero-range interactions using the adiabatic projection method. The adiabatic projection method uses a set of initial cluster states and Euclidean time projection to give a systematically improvable description of the low-lying scattering cluster states in a finite volume. We use L\"uscher's finite-volume relations to determine the s-wave, p-wave, and d-wave phase shifts. For comparison, we also compute exact lattice results using Lanczos iteration and continuum results using the Skorniakov-Ter-Martirosian equation. For our Monte Carlo calculations we use a new lattice algorithm called impurity lattice Monte Carlo. This algorithm can be viewed as a hybrid technique which incorporates elements of both worldline and auxiliary-field Monte Carlo simulations.}, number={6}, journal={PHYSICAL REVIEW C}, author={Elhatisari, Serdar and Lee, Dean}, year={2014}, month={Dec} }
 @article{rokash_epelbaum_krebs_lee_meissner_2014, title={Finite volume effects in low-energy neutron-deuteron scattering}, volume={41}, number={1}, journal={Journal of Physics. G, Nuclear and Particle Physics}, author={Rokash, A. and Epelbaum, E. and Krebs, H. and Lee, D. and Meissner, U. G.}, year={2014} }
 @article{laehde_epelbaum_krebs_lee_meissner_rupak_2014, title={Lattice effective field theory for medium-mass nuclei}, volume={732}, ISSN={["1873-2445"]}, DOI={10.1016/j.physletb.2014.03.023}, abstractNote={We extend Nuclear Lattice Effective Field Theory (NLEFT) to medium-mass nuclei, and present results for the ground states of alpha nuclei from 4He to 28Si, calculated up to next-to-next-to-leading order (NNLO) in the EFT expansion. This computational advance is made possible by extrapolations of lattice data using multiple initial and final states. For our soft two-nucleon interaction, we find that the overall contribution from multi-nucleon forces must change sign from attractive to repulsive with increasing nucleon number. This effect is not produced by three-nucleon forces at NNLO, but it can be approximated by an effective four-nucleon interaction. We discuss the convergence of the EFT expansion and the broad significance of our findings for future ab initio calculations.}, journal={PHYSICS LETTERS B}, author={Laehde, Timoa A. and Epelbaum, Evgeny and Krebs, Hermann and Lee, Dean and Meissner, Ulf-G. and Rupak, Gautam}, year={2014}, month={May}, pages={110–115} }
 @article{laehde_epelbaum_krebs_lee_meissner_rupak_2014, title={The Hoyle state in nuclear lattice effective field theory}, volume={83}, ISSN={["0973-7111"]}, DOI={10.1007/s12043-014-0861-z}, abstractNote={We review the calculation of the Hoyle state of 12C in nuclear lattice effective field theory (NLEFT) and its anthropic implications in the nucleosynthesis of 12C and 16O in red giant stars. We also analyse the extension of NLEFT to the regime of medium-mass nuclei, with emphasis on the determination of the ground-state energies of the α nuclei 16O, 20Ne, 24Mg, and 28Si by Euclidean time projection. Finally, we discuss recent NLEFT results for the spectrum, electromagnetic properties, and α-cluster structure of 16O.}, number={5}, journal={PRAMANA-JOURNAL OF PHYSICS}, author={Laehde, Timo A. and Epelbaum, Evgeny and Krebs, Hermann and Lee, Dean and Meissner, Ulf-G and Rupak, Gautam}, year={2014}, month={Nov}, pages={651–659} }
 @article{pine_lee_rupak_2013, title={Adiabatic projection method for scattering and reactions on the lattice}, volume={49}, ISSN={["1434-601X"]}, DOI={10.1140/epja/i2013-13151-3}, abstractNote={We demonstrate and test the adiabatic projection method, a general new framework for calculating scattering and reactions on the lattice. The method is based upon calculating a low-energy effective theory for clusters which becomes exact in the limit of large Euclidean projection time. As a detailed example we calculate the adiabatic two-body Hamiltonian for elastic fermion-dimer scattering in lattice effective field theory. Our calculation corresponds to neutron-deuteron scattering in the spin-quartet channel at leading order in pionless effective field theory. We show that the spectrum of the adiabatic Hamiltonian reproduces the spectrum of the original Hamiltonian below the inelastic threshold to arbitrary accuracy. We also show that the calculated s-wave phase shift reproduces the known exact result in the continuum and infinite-volume limits. When extended to more than one scattering channel, the adiabatic projection method can be used to calculate inelastic reactions on the lattice in future work.}, number={12}, journal={EUROPEAN PHYSICAL JOURNAL A}, author={Pine, Michelle and Lee, Dean and Rupak, Gautam}, year={2013}, month={Dec} }
 @article{koenig_lee_hammer_2013, title={Causality constraints for charged particles}, volume={40}, number={4}, journal={Journal of Physics. G, Nuclear and Particle Physics}, author={Koenig, S. and Lee, D. and Hammer, H. W.}, year={2013} }
 @article{elhatisari_koenig_lee_hammer_2013, title={Causality, universality, and effective field theory for van der Waals interactions}, volume={87}, ISSN={["1094-1622"]}, DOI={10.1103/physreva.87.052705}, abstractNote={We analyze low-energy scattering for arbitrary short-range interactions plus an attractive 1/r^6 tail. We derive the constraints of causality and unitarity and find that the van der Waals length scale dominates over parameters characterizing the short-distance physics of the interaction. This separation of scales suggests a separate universality class for physics characterizing interactions with an attractive 1/r^6 tail. We argue that a similar universality class exists for any attractive potential 1/r^{alpha} for alpha >= 2. We also discuss the extension to multi-channel systems near a magnetic Feshbach resonance. We discuss the implications for effective field theory with attractive singular power law tails.}, number={5}, journal={PHYSICAL REVIEW A}, publisher={American Physical Society}, author={Elhatisari, Serdar and Koenig, Sebastian and Lee, Dean and Hammer, H. -W.}, year={2013}, month={May} }
 @article{epelbaum_krebs_laehde_lee_meissner_2013, title={Dependence of the triple-alpha process on the fundamental constants of nature}, volume={49}, ISSN={["1434-601X"]}, DOI={10.1140/epja/i2013-13082-y}, abstractNote={We present an ab initio calculation of the quark mass dependence of the ground state energies of 4He , 8Be and 12C , and of the energy of the Hoyle state in 12C . These investigations are performed within the framework of lattice chiral Effective Field Theory. We address the sensitivity of the production rate of carbon and oxygen in red giant stars to the fundamental constants of nature by considering the impact of variations in the light quark masses and the electromagnetic fine-structure constant on the reaction rate of the triple-alpha process. As carbon and oxygen are essential to life as we know it, we also discuss the implications of our findings for an anthropic view of the Universe. We find strong evidence that the physics of the triple-alpha process is driven by alpha clustering, and that shifts in the fundamental parameters at the ≃ 2–3% level are unlikely to be detrimental to the development of life. Tolerance against much larger changes cannot be ruled out at present, given the relatively limited knowledge of the quark mass dependence of the two-nucleon S -wave scattering parameters. Lattice QCD is expected to provide refined estimates of the scattering parameters in the future.}, number={7}, journal={EUROPEAN PHYSICAL JOURNAL A}, author={Epelbaum, Evgeny and Krebs, Hermann and Laehde, Timo A. and Lee, Dean and Meissner, Ulf-G.}, year={2013}, month={Jul} }
 @article{pine_lee_2013, title={Effective field theory for bound state reflection}, volume={331}, ISSN={["1096-035X"]}, DOI={10.1016/j.aop.2012.12.009}, abstractNote={Elastic quantum bound-state reflection from a hard-wall boundary provides direct information regarding the structure and compressibility of quantum bound states. We discuss elastic quantum bound-state reflection and derive a general theory for elastic reflection of shallow dimers from hard-wall surfaces using effective field theory. We show that there is a small expansion parameter for analytic calculations of the reflection scattering length. We present a calculation up to second order in the effective Hamiltonian in one, two, and three dimensions. We also provide numerical lattice results for all three cases as a comparison with our effective field theory results. Finally, we provide an analysis of the compressibility of the alpha particle confined to a cubic lattice with vanishing Dirichlet boundaries.}, journal={ANNALS OF PHYSICS}, author={Pine, Michelle and Lee, Dean}, year={2013}, month={Apr}, pages={24–50} }
 @article{rupak_lee_2013, title={Radiative Capture Reactions in Lattice Effective Field Theory}, volume={111}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.111.032502}, abstractNote={We outline a general method for computing nuclear capture reactions on the lattice. The method consists of two major parts. In this study we detail the second part which consists of calculating an effective two-body capture reaction on the lattice at finite volume. We solve this problem by calculating the two-point Green's function using an infrared regulator and the capture amplitude to a two-body bound state. We demonstrate the details of this method by calculating on the lattice the leading M1 contribution to the radiative neutron capture on proton at low energies using pionless effective field theory. We find good agreement with exact continuum results. The approach we outline here can be used in a wide range of applications including few-body reactions in cold atomic systems and hadronic reactions in lattice quantum chromodynamics.}, number={3}, journal={PHYSICAL REVIEW LETTERS}, author={Rupak, Gautam and Lee, Dean}, year={2013}, month={Jul} }
 @article{epelbaum_krebs_laehde_lee_meissner_2013, title={Viability of Carbon-Based Life as a Function of the Light Quark Mass}, volume={110}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.110.112502}, abstractNote={The Hoyle state plays a crucial role in the helium burning of stars that have reached the red giant stage. The close proximity of this state to the triple-alpha threshold is needed for the production of carbon, oxygen, and other elements necessary for life. We investigate whether this life-essential condition is robust or delicately fine-tuned by measuring its dependence on the fundamental constants of nature, specifically the light quark mass and the strength of the electromagnetic interaction. We show that there exist strong correlations between the alpha-particle binding energy and the various energies relevant to the triple-alpha process. We derive limits on the variation of these fundamental parameters from the requirement that sufficient amounts of carbon and oxygen be generated in stars. We also discuss the implications of our results for an anthropic view of the Universe.}, number={11}, journal={PHYSICAL REVIEW LETTERS}, author={Epelbaum, Evgeny and Krebs, Hermann and Laehde, Timo A. and Lee, Dean and Meissner, Ulf-G.}, year={2013}, month={Mar} }
 @article{bour_hammer_lee_meissner_2012, title={Benchmark calculations for elastic fermion-dimer scattering}, volume={86}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.86.034003}, abstractNote={We present continuum and lattice calculations for elastic scattering between a fermion and a bound dimer in the shallow binding limit. For the continuum calculation we use the Skorniakov-Ter-Martirosian (STM) integral equation to determine the scattering length and effective range parameter to high precision. For the lattice calculation we use the finite-volume method of L\"uscher. We take into account topological finite-volume corrections to the dimer binding energy which depend on the momentum of the dimer. After subtracting these effects, we find from the lattice calculation kappa a_fd = 1.174(9) and kappa r_fd = -0.029(13). These results agree well with the continuum values kappa a_fd = 1.17907(1) and kappa r_fd = -0.0383(3) obtained from the STM equation. We discuss applications to cold atomic Fermi gases, deuteron-neutron scattering in the spin-quartet channel, and lattice calculations of scattering for nuclei and hadronic molecules at finite volume.}, number={3}, journal={PHYSICAL REVIEW C}, author={Bour, Shahin and Hammer, H. -W. and Lee, Dean and Meissner, Ulf-G.}, year={2012}, month={Sep} }
 @article{elhatisari_lee_2012, title={Causality bounds for neutron-proton scattering}, volume={48}, ISSN={["1434-601X"]}, DOI={10.1140/epja/i2012-12110-x}, abstractNote={We consider the constraints of causality and unitarity for the low-energy interactions of protons and neutrons. We derive a general theorem that non-vanishing partial-wave mixing cannot be reproduced with zero-range interactions without violating causality or unitarity. We define and calculate interaction length scales which we call the causal range and the Cauchy-Schwarz range for all spin channels up to J = 3 . For some channels we find that these length scales are as large as 5fm. We investigate the origin of these large lengths and discuss their significance for the choice of momentum cutoff scales in effective field theory and universality in many-body Fermi systems.}, number={8}, journal={EUROPEAN PHYSICAL JOURNAL A}, author={Elhatisari, S. and Lee, D.}, year={2012}, month={Aug} }
 @article{koenig_lee_hammer_2012, title={Non-relativistic bound states in a finite volume}, volume={327}, ISSN={["0003-4916"]}, DOI={10.1016/j.aop.2011.12.015}, abstractNote={We derive general results for the mass shift of bound states with angular momentum ℓ≥1 in a periodic cubic box in two and three spatial dimensions. Our results have applications to lattice simulations of hadronic molecules, halo nuclei, and Feshbach molecules. The sign of the mass shift can be related to the symmetry properties of the state under consideration. We verify our analytical results with explicit numerical calculations. Moreover, we comment on the relations connecting the effective range parameter, the binding momentum of a given state and the asymptotic normalization coefficient of the corresponding wave function. We give explicit expressions for this relation in the shallow binding limit.}, number={6}, journal={ANNALS OF PHYSICS}, publisher={Elsevier }, author={Koenig, Sebastian and Lee, Dean and Hammer, H. -W.}, year={2012}, month={Jun}, pages={1450–1471} }
 @article{epelbaum_krebs_laehde_lee_meissner_2012, title={Structure and Rotations of the Hoyle State}, volume={109}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.109.252501}, abstractNote={The excited state of the (12)C nucleus known as the "Hoyle state" constitutes one of the most interesting, difficult, and timely challenges in nuclear physics, as it plays a key role in the production of carbon via fusion of three alpha particles in red giant stars. In this Letter, we present ab initio lattice calculations which unravel the structure of the Hoyle state, along with evidence for a low-lying spin-2 rotational excitation. For the (12)C ground state and the first excited spin-2 state, we find a compact triangular configuration of alpha clusters. For the Hoyle state and the second excited spin-2 state, we find a "bent-arm" or obtuse triangular configuration of alpha clusters. We also calculate the electromagnetic transition rates between the low-lying states of (12)C.}, number={25}, journal={PHYSICAL REVIEW LETTERS}, author={Epelbaum, Evgeny and Krebs, Hermann and Laehde, Timo A. and Lee, Dean and Meissner, Ulf-G.}, year={2012}, month={Dec} }
 @article{nishida_lee_2012, title={Weakly bound molecules trapped with discrete scaling symmetries}, volume={86}, ISSN={["1094-1622"]}, DOI={10.1103/physreva.86.032706}, abstractNote={When the scattering length is proportional to the distance from the center of the system, two particles are shown to be trapped about the center. Furthermore, their spectrum exhibits discrete scale invariance, whose scale factor is controlled by the slope of the scattering length. While this resembles the Efimov effect, our system has a number of advantages when realized with ultracold atoms. We also elucidate how the emergent discrete scaling symmetry is violated for more than two bosons, which may shed new light on Efimov physics. Our system thus serves as a tunable model system to investigate universal physics involving scale invariance, quantum anomaly, and renormalization group limit cycle, which are important in a broad range of quantum physics.}, number={3}, journal={PHYSICAL REVIEW A}, author={Nishida, Yusuke and Lee, Dean}, year={2012}, month={Sep} }
 @article{epelbaum_krebs_lee_meissner_2011, title={Ab Initio Calculation of the Hoyle State}, volume={106}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.106.192501}, abstractNote={The Hoyle state plays a crucial role in the helium burning of stars heavier than our Sun and in the production of carbon and other elements necessary for life. This excited state of the carbon-12 nucleus was postulated by Hoyle as a necessary ingredient for the fusion of three alpha particles to produce carbon at stellar temperatures. Although the Hoyle state was seen experimentally more than a half century ago nuclear theorists have not yet uncovered the nature of this state from first principles. In this Letter we report the first ab initio calculation of the low-lying states of carbon-12 using supercomputer lattice simulations and a theoretical framework known as effective field theory. In addition to the ground state and excited spin-2 state, we find a resonance at -85(3)  MeV with all of the properties of the Hoyle state and in agreement with the experimentally observed energy.}, number={19}, journal={PHYSICAL REVIEW LETTERS}, author={Epelbaum, Evgeny and Krebs, Hermann and Lee, Dean and Meissner, Ulf-G.}, year={2011}, month={May} }
 @article{bour_li_lee_meissner_mitas_2011, title={Precision benchmark calculations for four particles at unitarity}, volume={83}, ISSN={["1094-1622"]}, DOI={10.1103/physreva.83.063619}, abstractNote={The unitarity limit describes interacting particles where the range of the interaction is zero and the scattering length is infinite. We present precision benchmark calculations for two-component fermions at unitarity using three different ab initio methods: Hamiltonian lattice formalism using iterated eigenvector methods, Euclidean lattice formalism with auxiliary-field projection Monte Carlo methods, and continuum diffusion Monte Carlo methods with fixed and released nodes. We have calculated the ground-state energy of the unpolarized four-particle system in a periodic cube as a dimensionless fraction of the ground-state energy for the noninteracting system. We obtain values of 0.211(2) and 0.210(2) using two different Hamiltonian lattice representations, 0.206(9) using Euclidean lattice formalism, and an upper bound of 0.212(2) from fixed-node diffusion Monte Carlo methods. Released-node calculations starting from the fixed-node result yield a decrease of less than 0.002 over a propagation of 0.4E{sub F}{sup -1} in Euclidean time, where E{sub F} is the Fermi energy. We find good agreement among all three ab initio methods.}, number={6}, journal={PHYSICAL REVIEW A}, author={Bour, Shahin and Li, Xin and Lee, Dean and Meissner, Ulf-G. and Mitas, Lubos}, year={2011}, month={Jun} }
 @article{koenig_lee_hammer_2011, title={Volume Dependence of Bound States with Angular Momentum}, volume={107}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.107.112001}, abstractNote={We derive general results for the mass shift of bound states with angular momentum ℓ≥1 in a finite periodic volume. Our results have direct applications to lattice simulations of hadronic molecules as well as atomic nuclei. While the binding of S-wave bound states increases at finite volume, we show that the binding of P-wave bound states decreases. The mass shift for D-wave bound states as well as higher partial waves depends on the representation of the cubic rotation group. Nevertheless, the multiplet-averaged mass shift for any angular momentum ℓ can be expressed in a simple form, and the sign of the shift alternates for even and odd ℓ. We verify our analytical results with explicit numerical calculations. We also show numerically that similar volume corrections appear in three-body bound states.}, number={11}, journal={PHYSICAL REVIEW LETTERS}, publisher={American Physical Society}, author={Koenig, Sebastian and Lee, Dean and Hammer, H. -W.}, year={2011}, month={Sep} }
 @article{hammer_lee_2010, title={Causality and the effective range expansion}, volume={325}, ISSN={["1096-035X"]}, DOI={10.1016/j.aop.2010.06.006}, abstractNote={We derive the generalization of Wigner’s causality bounds and Bethe’s integral formula for the effective range parameter to arbitrary dimension and arbitrary angular momentum. We also discuss the impact of these constraints on the separation of low- and high-momentum scales and universality in low-energy scattering. Some of our results were summarized earlier in a letter publication. In this work, we present full derivations and several detailed examples.}, number={10}, journal={ANNALS OF PHYSICS}, author={Hammer, H. -W. and Lee, Dean}, year={2010}, month={Oct}, pages={2212–2233} }
 @article{epelbaum_krebs_lee_meiner_2010, title={Lattice Effective Field Theory Calculations for A = 3, 4, 6, 12 Nuclei}, volume={104}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.104.142501}, abstractNote={We present lattice results for the ground state energies of tritium, helium-3, helium-4, lithium-6, and carbon-12 nuclei. Our analysis includes isospin breaking, Coulomb effects, and interactions up to next-to-next-to-leading order in chiral effective field theory.}, number={14}, journal={PHYSICAL REVIEW LETTERS}, author={Epelbaum, Evgeny and Krebs, Hermann and Lee, Dean and Meiner, Ulf-G.}, year={2010}, month={Apr} }
 @article{epelbaum_krebs_lee_meissner_2010, title={Lattice calculations for A=3, 4, 6, 12 nuclei using chiral effective field theory}, volume={45}, ISSN={["1434-6001"]}, DOI={10.1140/epja/i2010-11009-x}, abstractNote={We present lattice calculations for the ground state energies of tritium, helium-3, helium-4, lithium-6, and carbon-12 nuclei. Our results were previously summarized in a letter publication. This paper provides full details of the calculations. We include isospin-breaking, Coulomb effects, and interactions up to next-to-next-to-leading order in chiral effective field theory.}, number={3}, journal={EUROPEAN PHYSICAL JOURNAL A}, author={Epelbaum, E. and Krebs, H. and Lee, D. and Meissner, U. -G.}, year={2010}, month={Sep}, pages={335–352} }
 @article{hammer_lee_2009, title={Causality and universality in low-energy quantum scattering}, volume={681}, ISSN={["1873-2445"]}, DOI={10.1016/j.physletb.2009.10.033}, abstractNote={We generalize Wigner's causality bounds and Bethe's integral formula for the effective range to arbitrary dimension and arbitrary angular momentum. Moreover, we discuss the impact of these constraints on the separation of low- and high-momentum scales and universality in low-energy quantum scattering.}, number={5}, journal={PHYSICS LETTERS B}, author={Hammer, H. -W. and Lee, Dean}, year={2009}, month={Nov}, pages={500–503} }
 @inproceedings{lee_hammer_2009, title={Causality and universality in low-energy scattering}, volume={3}, booktitle={19th international iupap conference on few-body problems in physics}, author={Lee, D. and Hammer, H. W.}, year={2009} }
 @article{epelbaum_krebs_lee_meissner_2009, title={Ground-state energy of dilute neutron matter at next-to-leading order in lattice chiral effective field theory}, volume={40}, ISSN={["1434-601X"]}, DOI={10.1140/epja/i2009-10755-0}, abstractNote={We present lattice calculations for the ground state energy of dilute neutron matter at next-to-leading order in chiral effective field theory. This study follows a series of recent papers on low-energy nuclear physics using chiral effective field theory on the lattice. In this work we introduce an improved spin- and isospin-projected leading-order action which allows for a perturbative treatment of corrections at next-to-leading order and smaller estimated errors. Using auxiliary fields and Euclidean-time projection Monte Carlo, we compute the ground state of 8, 12, and 16 neutrons in a periodic cube, covering a density range from 2% to 10% of normal nuclear density.}, number={2}, journal={EUROPEAN PHYSICAL JOURNAL A}, author={Epelbaum, E. and Krebs, H. and Lee, D. and Meissner, U. -G.}, year={2009}, month={May}, pages={199–213} }
 @article{epelbaum_krebs_lee_meissner_2009, title={Lattice chiral effective field theory with three-body interactions at next-to-next-to-leading order}, volume={41}, ISSN={["1434-6001"]}, DOI={10.1140/epja/i2009-10764-y}, abstractNote={We consider low-energy nucleons at next-to-next-to-leading order in lattice chiral effective field theory. Three-body interactions first appear at this order, and we discuss several methods for determining three-body interaction coefficients on the lattice. We compute the energy of the triton and low-energy neutron-deuteron scattering phase shifts in the spin-doublet and spin-quartet channels using Lüscher’s finite-volume method. In the four-nucleon system we calculate the energy of the $ \alpha$ -particle using auxiliary fields and projection Monte Carlo.}, number={1}, journal={EUROPEAN PHYSICAL JOURNAL A}, author={Epelbaum, E. and Krebs, H. and Lee, D. and Meissner, U. -G.}, year={2009}, month={Jul}, pages={125–139} }
 @misc{lee_2009, title={Lattice simulations for few- and many-body systems}, volume={63}, ISBN={["*****************"]}, ISSN={["0146-6410"]}, DOI={10.1016/j.ppnp.2008.12.001}, abstractNote={We review the recent literature on lattice simulations for few- and many-body systems. We focus on methods and results that combine the framework of effective field theory with computational lattice methods. Lattice effective field theory is discussed for cold atoms as well as low-energy nucleons with and without pions. A number of different lattice formulations and computational algorithms are considered, and an effort is made to show common themes in studies of cold atoms and low-energy nuclear physics as well as common themes in work by different collaborations.}, number={1}, journal={PROGRESS IN PARTICLE AND NUCLEAR PHYSICS, VOL 63, NO 1}, author={Lee, Dean}, year={2009}, pages={117–154} }
 @inproceedings{lee_epelbaum_krebs_meissner_2009, title={Nuclear lattice simulations}, volume={3}, booktitle={19th international iupap conference on few-body problems in physics}, author={Lee, D. and Epelbaum, E. and Krebs, H. and Meissner, U. G.}, year={2009} }
 @article{borasoy_epelbaum_krebs_lee_meissner_2008, title={Chiral effective field theory on the lattice at next-to-leading order}, volume={35}, ISSN={["1434-6001"]}, DOI={10.1140/epja/i2008-10544-3}, abstractNote={We study nucleon-nucleon scattering on the lattice at next-to-leading order in chiral effective field theory. We determine phase shifts and mixing angles from the properties of two-nucleon standing waves induced by a hard spherical wall in the center-of-mass frame. At fixed lattice spacing we test model independence of the low-energy effective theory by computing next-to-leading-order corrections for two different leading-order lattice actions. The first leading-order action includes instantaneous one-pion exchange and same-site contact interactions. The second leading-order action includes instantaneous one-pion exchange and Gaussian-smeared interactions. We find that in each case the results at next-to-leading order are accurate up to corrections expected at higher order.}, number={3}, journal={EUROPEAN PHYSICAL JOURNAL A}, author={Borasoy, B. and Epelbaum, E. and Krebs, H. and Lee, D. and Meissner, U.-G.}, year={2008}, month={Mar}, pages={343–355} }
 @article{borasoy_epelbaum_krebs_lee_meissner_2008, title={Dilute neutron matter on the lattice at next-to-leading order in chiral effective field theory}, volume={35}, ISSN={["1434-601X"]}, DOI={10.1140/epja/i2008-10545-2}, abstractNote={We discuss lattice simulations of the ground state of dilute neutron matter at next-to-leading order in chiral effective field theory. In a previous paper the coefficients of the next-to-leading-order lattice action were determined by matching nucleon-nucleon scattering data for momenta up to the pion mass. Here the same lattice action is used to simulate the ground state of up to 12 neutrons in a periodic cube using Monte Carlo simulations. We explore the density range from 2% to 8% of normal nuclear density and analyze the ground-state energy as an expansion about the unitarity limit with corrections due to finite scattering length, effective range, and P -wave interactions.}, number={3}, journal={EUROPEAN PHYSICAL JOURNAL A}, author={Borasoy, B. and Epelbaum, E. and Krebs, H. and Lee, D. and Meissner, U. -G.}, year={2008}, month={Mar}, pages={357–367} }
 @article{lee_2008, title={Ground state energy at unitarity}, volume={78}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.78.024001}, abstractNote={We consider two-component fermions on the lattice in the unitarity limit. This is an idealized limit of attractive fermions where the range of the interaction is zero and the scattering length is infinite. Using Euclidean time projection, we compute the ground state energy using four computationally different but physically identical auxiliary-field methods. The best performance is obtained using a bounded continuous auxiliary field and a nonlocal updating algorithm called the hybrid Monte Carlo. With this method, we calculate results for 10 and 14 fermions at lattice volumes 4{sup 3},5{sup 3},6{sup 3},7{sup 3},8{sup 3} and extrapolate to the continuum limit. For 10 fermions in a periodic cube, the ground state energy is 0.292(12) times the ground state energy for noninteracting fermions. For 14 fermions, the ratio is 0.329(5)}, number={2}, journal={PHYSICAL REVIEW C}, author={Lee, Dean}, year={2008}, month={Aug} }
 @article{lee_2008, title={The symmetric heavy-light ansatz}, volume={35}, ISSN={["1434-601X"]}, DOI={10.1140/epja/i2008-10537-2}, abstractNote={The symmetric heavy-light ansatz is a method for finding the ground state of any dilute unpolarized system of attractive two-component fermions. Operationally it can be viewed as a generalization of the Kohn-Sham equations in density functional theory applied to N -body density correlations. While the original Hamiltonian has an exact Z2 symmetry, the heavy-light ansatz breaks this symmetry by skewing the mass ratio of the two components. In the limit where one component is infinitely heavy, the many-body problem can be solved in terms of single-particle orbitals. The original Z2 symmetry is recovered by enforcing Z2 symmetry as a constraint on N -body density correlations for the two components. For the 1D, 2D, and 3D attractive Hubbard models the method is in very good agreement with exact Lanczos calculations for few-body systems at arbitrary coupling. For the 3D attractive Hubbard model there is very good agreement with lattice Monte Carlo results for many-body systems in the limit of infinite scattering length.}, number={2}, journal={EUROPEAN PHYSICAL JOURNAL A}, author={Lee, D.}, year={2008}, month={Feb}, pages={171–187} }
 @article{borasoy_epelbaum_krebs_lee_meissner_2007, title={Lattice simulations for light nuclei: Chiral effective field theory at leading order}, volume={31}, ISSN={["1434-601X"]}, DOI={10.1140/epja/i2006-10154-1}, abstractNote={We discuss lattice simulations of light nuclei at leading order in the chiral effective field theory. Using lattice pion fields and auxiliary fields, we include the physics of instantaneous one-pion exchange and the leading-order S-wave contact interactions. We also consider higher-derivative contact interactions which adjust the S-wave scattering amplitude at higher momenta. By construction our lattice path integral is positive definite in the limit of exact Wigner SU(4) symmetry for any even number of nucleons. This SU(4) positivity and the approximate SU(4) symmetry of the low-energy interactions play an important role in suppressing sign and phase oscillations in Monte Carlo simulations. We assess the computational scaling of the lattice algorithm for light nuclei with up to eight nucleons and analyze in detail calculations of the deuteron, triton, and helium-4.}, number={1}, journal={EUROPEAN PHYSICAL JOURNAL A}, author={Borasoy, B. and Epelbaum, E. and Krebs, H. and Lee, D. and Meissner, U. -G.}, year={2007}, month={Jan}, pages={105–123} }
 @article{lee_2007, title={Recent results from nuclear lattice simulations}, volume={22}, ISSN={["0217-7323"]}, DOI={10.1142/S0217732307023134}, abstractNote={ We discuss recent progress in the study of nuclear and neutron matter by combining chiral effective field theory with non-perturbative lattice methods. We present results for hot neutron matter at temperatures 20 to 40 MeV and densities below twice nuclear matter density. This proceedings article is a summary of results from work done in collaboration with Bugra Borasoy and Thomas Schaefer1. }, number={7-10}, journal={MODERN PHYSICS LETTERS A}, author={Lee, Dean}, year={2007}, month={Mar}, pages={555–564} }
 @article{lee_2007, title={Spectral convexity for attractive SU(2N) fermions}, volume={98}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.98.182501}, abstractNote={We prove a general theorem on spectral convexity with respect to particle number for 2N degenerate components of fermions. The number of spatial dimensions is arbitrary, and the system may be uniform or constrained by an external potential. We assume only that the interactions are governed by an SU(2N)-invariant two-body potential whose Fourier transform is negative definite. The convexity result implies that the ground state is in a 2N-particle clustering phase. We discuss implications for light nuclei as well as asymmetric nuclear matter in neutron stars.}, number={18}, journal={PHYSICAL REVIEW LETTERS}, author={Lee, Dean}, year={2007}, month={May} }
 @article{lee_2007, title={Superfluidity and excitations at unitarity}, volume={75}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.75.134502}, abstractNote={We present lattice results for spin-$1∕2$ fermions at unitarity, where the effective range of the interaction is zero and the scattering length is infinite. We measure the spatial coherence of difermion pairs for a system of 6, 10, 14, 18, 22, 26 particles with equal numbers of up and down spins in a periodic cube. Using Euclidean time projection, we analyze ground-state properties and transient behavior due to low-energy excitations. At asymptotically large values of $t$ we see long-range order consistent with spontaneously broken U(1) fermion-number symmetry and a superfluid ground state. At intermediate times we see exponential decay in the $t$-dependent signal due to an unknown low-energy excitation. We probe this low-energy excitation further by calculating two-particle correlation functions. We find that the excitation has the properties of a chain of particles extending across the periodic lattice.}, number={13}, journal={PHYSICAL REVIEW B}, author={Lee, Dean}, year={2007}, month={Apr} }
 @article{lee_thomson_2007, title={Temperature-dependent errors in nuclear lattice simulations}, volume={75}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.75.064003}, abstractNote={We study the temperature dependence of discretization errors in nuclear lattice simulations. We find that for systems with strong attractive interactions the predominant error arises from the breaking of Galilean invariance. We propose a local 'well-tempered' lattice action which eliminates much of this error. The well-tempered action can be readily implemented in lattice simulations for nuclear systems as well as cold atomic Fermi systems.}, number={6}, journal={PHYSICAL REVIEW C}, author={Lee, Dean and Thomson, Richard}, year={2007}, month={Jun} }
 @article{borasoy_epelbaum_krebs_lee_meissner_2007, title={Two-particle scattering on the lattice: Phase shifts, spin-orbit coupling, and mixing angles}, volume={34}, ISSN={["1434-601X"]}, DOI={10.1140/epja/i2007-10500-9}, abstractNote={We determine two-particle scattering phase shifts and mixing angles for quantum theories defined with lattice regularization. The method is suitable for any non-relativistic effective theory of point particles on the lattice. In the center-of-mass frame of the two-particle system we impose a hard spherical wall at some fixed large radius. For channels without partial-wave mixing the partial-wave phase shifts are determined from the energies of the nearly spherical standing waves. For channels with partial-wave mixing further information is extracted by decomposing the standing wave at the wall boundary into spherical harmonics, and we solve coupled-channels equations to extract the phase shifts and mixing angles. The method is illustrated and tested by computing phase shifts and mixing angles on the lattice for spin-1/2 particles with an attractive Gaussian potential containing both central and tensor force parts.}, number={2}, journal={EUROPEAN PHYSICAL JOURNAL A}, author={Borasoy, B. and Epelbaum, E. and Krebs, H. and Lee, D. and Meissner, U. -G.}, year={2007}, month={Nov}, pages={185–196} }
 @article{lee_schafer_2006, title={Cold dilute neutron matter on the lattice. I. Lattice virial coefficients and large scattering lengths}, volume={73}, ISSN={["1089-490X"]}, url={http://inspirehep.net/record/691674}, DOI={10.1103/physrevc.73.015201}, abstractNote={We study cold dilute neutron matter on the lattice using an effective field theory. We work in the unitary limit in which the scattering length is much larger than the interparticle spacing. In this article we focus on the equation of state at temperatures above the Fermi temperature and compare lattice simulations to the virial expansion on the lattice and in the continuum. We find that in the unitary limit lattice discretization errors in the second virial coefficient are significantly enhanced. As a consequence the equation of state does not show the universal scaling behavior expected in the unitary limit. We suggest that scaling can be improved by tuning the second virial coefficient rather than the scattering length.}, number={1}, journal={PHYSICAL REVIEW C}, author={Lee, D and Schafer, T}, year={2006}, month={Jan} }
 @article{lee_schafer_2006, title={Cold dilute neutron matter on the lattice. II. Results in the unitary limit}, volume={73}, ISSN={["1089-490X"]}, url={http://inspirehep.net/record/691675}, DOI={10.1103/physrevc.73.015202}, abstractNote={This is the second of two articles that investigate cold dilute neutron matter on the lattice using pionless effective field theory. In the unitary limit, where the effective range is zero and scattering length is infinite, simple scaling relations relate thermodynamic functions at different temperatures. When the second virial coefficient is properly tuned, we find that the lattice results obey these scaling relations. We compute the energy per particle, pressure, spin susceptibility, dineutron correlation function, and an upper bound for the superfluid critical temperature.}, number={1}, journal={PHYSICAL REVIEW C}, author={Lee, D and Schafer, T}, year={2006}, month={Jan} }
 @article{lee_2006, title={Ground-state energy of spin-(1)/(2) fermions in the unitary limit}, volume={73}, ISSN={["1550-235X"]}, DOI={10.1103/physrevb.73.115112}, abstractNote={We present lattice results for the ground-state energy of a spin-(1/2) fermion system in the unitary limit, where the effective range of the interaction is zero and the scattering length is infinite. We compute the ground-state energy for a system of 6, 10, 14, 18, and 22 particles, with equal numbers of up and down spins in a periodic cube. We estimate that in the limit of large number of particles, the ground-state energy is 0.25(3) times the ground-state energy of the free Fermi system.}, number={11}, journal={PHYSICAL REVIEW B}, author={Lee, D}, year={2006}, month={Mar} }
 @article{lee_2006, title={Large-N droplets in two dimensions}, volume={73}, ISSN={["1094-1622"]}, DOI={10.1103/physreva.73.063204}, abstractNote={Using lattice effective field theory, we study the ground state binding energy of N distinct particles in two dimensions with equal mass interacting weakly via an attractive SU(N)-symmetric short range potential. We find that in the limit of zero range and large N, the ratio of binding energies B{sub N}/B{sub N-1} approaches the value 8.3(6)}, number={6}, journal={PHYSICAL REVIEW A}, author={Lee, Dean}, year={2006}, month={Jun} }
 @article{hamilton_lynch_lee_2005, title={Lattice gas models derived from effective field theory}, volume={71}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.71.044005}, abstractNote={We start from a low-energy effective field theory for interacting fermions on the lattice and expand in the hopping parameter to derive the nearest-neighbor interactions for a lattice gas model. In this model, the renormalization of couplings for different lattice spacings is inherited from the effective field theory, systematic errors can be estimated a priori, and the breakdown of the lattice gas model description at low temperatures can be understood quantitatively. We apply the lattice gas method to neutron matter and compare with results from a recent quantum simulation.}, number={4}, journal={PHYSICAL REVIEW C}, author={Hamilton, M and Lynch, I and Lee, D}, year={2005}, month={Apr} }
 @article{lee_schafer_2005, title={Neutron matter on the lattice with pionless effective field theory}, volume={72}, ISSN={["1089-490X"]}, url={http://inspirehep.net/record/665772}, DOI={10.1103/physrevc.72.024006}, abstractNote={We study neutron matter by combining pionless effective field theory with non-perturbative lattice methods. The neutron contact interaction is determined by zero temperature scattering data. We simulate neutron matter on the lattice at temperatures 4 and 8 MeV and densities below one-fifth normal nuclear matter density. Our results at different lattice spacings agree with one another and match bubble chain calculations at low densities. The equation of state of pure neutron matter obtained from our simulations agrees quantitatively with variational calculations based on realistic potentials.}, number={2}, journal={PHYSICAL REVIEW C}, author={Lee, D and Schafer, T}, year={2005}, month={Aug} }
 @article{lee_2005, title={Nuclear lattice simulations with EFT}, volume={140}, ISSN={["0920-5632"]}, DOI={10.1016/j.nuclphysbps.2004.11.273}, abstractNote={This proceedings article is a summary of results from work done in collaboration with Buḡra Borasoy and Thomas Schaefer. We study nuclear and neutron matter by combining chiral effective field theory with non-perturbative lattice methods. We present results for hot neutron matter at temperatures 20 to 40 MeV and densities below twice nuclear matter density.}, journal={NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS}, author={Lee, D}, year={2005}, month={Mar}, pages={577–579} }
 @article{lee_2005, title={Pressure inequalities for nuclear and neutron matter}, volume={71}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.71.044001}, abstractNote={We prove several inequalities using lowest-order effective field theory for nucleons which give an upper bound on the pressure of asymmetric nuclear matter and neutron matter. We prove two types of inequalities, one based on convexity and another derived from shifting an auxiliary field.}, number={4}, journal={PHYSICAL REVIEW C}, author={Lee, D}, year={2005}, month={Apr} }
 @article{chen_lee_schaefer_2004, title={Inequalities for light nuclei in the Wigner symmetry limit}, volume={93}, ISSN={["1079-7114"]}, url={http://inspirehep.net/record/656802}, DOI={10.1103/physrevlett.93.242302}, abstractNote={Using effective field theory we derive inequalities for light nuclei in the Wigner symmetry limit. This is the limit where isospin and spin degrees of freedom can be interchanged. We prove that the energy of any three-nucleon state is bounded below by the average energy of the lowest two-nucleon and four-nucleon states. We show how this is modified by lowest-order terms breaking Wigner symmetry and prove general energy convexity results for SU(N). We also discuss the inclusion of Wigner-symmetric three- and four-nucleon force terms.}, number={24}, journal={PHYSICAL REVIEW LETTERS}, author={Chen, JW and Lee, D and Schaefer, T}, year={2004}, month={Dec} }
 @article{lee_2004, title={Inequalities for low-energy symmetric nuclear matter}, volume={70}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.70.064002}, abstractNote={Using effective field theory we prove inequalities for the correlations of two-nucleon operators in low-energy symmetric nuclear matter. For physical values of operator coefficients in the effective Lagrangian, the $S=1,I=0$ channel correlations must have the lowest energy and longest correlation length in the two-nucleon sector. This result is valid at nonzero density and temperature.}, number={6}, journal={PHYSICAL REVIEW C}, author={Lee, D}, year={2004}, month={Dec} }
 @article{lee_borasoy_schaefer_2004, title={Nuclear lattice simulations with chiral effective field theory}, volume={70}, number={1}, journal={Physical Review. C, Nuclear Physics}, author={Lee, D. and Borasoy, B. and Schaefer, T.}, year={2004}, pages={014007} }
 @article{maris_lee_2003, title={Chiral symmetry breaking in (2+1) dimensional QED}, volume={119}, DOI={10.1016/S0920-5632(03)01683-9}, number={2003 May}, journal={Nuclear Physics. B, Proceedings, Supplements}, author={Maris, P. and Lee, D.}, year={2003}, pages={784–786} }
 @article{lee_maris_2003, title={Massless three-dimensional Qed with explicit fermions}, volume={67}, number={7}, journal={Physical Review. D, Particles and Fields}, author={Lee, D. and Maris, P.}, year={2003}, pages={076002–1} }
 @article{lee_ipsen_2003, title={Zone determinant expansions for nuclear lattice simulations}, volume={68}, ISSN={["1089-490X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85035272077&partnerID=MN8TOARS}, DOI={10.1103/physrevc.68.064003}, abstractNote={We introduce a new approximation to nucleon matrix determinants that is physically motivated by chiral effective theory. The method involves breaking the lattice into spatial zones and expanding the determinant in powers of the boundary hopping parameter.}, number={6}, journal={PHYSICAL REVIEW C}, author={Lee, DJ and Ipsen, ICF}, year={2003}, month={Dec} }
 @article{lee_2003, title={Zone methods and the fermion sign problem}, volume={119}, ISSN={["0920-5632"]}, DOI={10.1016/S0920-5632(03)01736-5}, abstractNote={We review a recently proposed approach to the problem of alternating signs for fermionic many body Monte Carlo simulations in finite temperature simulations. We derive an estimate for fermion wandering lengths and introduce the notion of permutation zones, special regions of the lattice where identical fermions may interchange and outside of which they may not. Using successively larger permutation zones, one can extrapolate to obtain thermodynamic observables in regimes where direct simulation is impossible.}, journal={NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS}, author={Lee, D}, year={2003}, month={May}, pages={979–981} }
 @article{lee_2002, title={Dynamical fermions in Hamiltonian lattice gauge theory}, volume={106}, ISSN={["1873-3832"]}, DOI={10.1016/S0920-5632(01)01924-7}, abstractNote={We describe a first attempt to understand dynamical fermions within a Hamiltonian framework. As a testing ground we study compact QED3, which shares some important features of QCD4 such as confinement, glueballs, mesons, and chiral symmetry breaking. We discuss the methods used and show data for the chiral condensate.}, journal={NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS}, author={Lee, D}, year={2002}, month={Mar}, pages={1049–1051} }