@article{kozcaz_sulejmanpasic_tanizaki_unsal_2018, title={Cheshire Cat Resurgence, Self-Resurgence and Quasi-Exact Solvable Systems}, volume={364}, ISSN={["1432-0916"]}, url={http://inspirehep.net/record/1487463}, DOI={10.1007/s00220-018-3281-y}, abstractNote={We explore a one parameter $\zeta$-deformation of the quantum-mechanical Sine-Gordon and Double-Well potentials which we call the Double Sine-Gordon (DSG) and the Tilted Double Well (TDW), respectively. In these systems, for positive integer values of $\zeta$, the lowest $\zeta$ states turn out to be exactly solvable for DSG - a feature known as Quasi-Exact-Solvability (QES) - and solvable to all orders in perturbation theory for TDW. For DSG such states do not show any instanton-like dependence on the coupling constant, although the action has real saddles. On the other hand, although it has no real saddles, the TDW admits all-orders perturbative states that are not normalizable, and hence, requires a non-perturbative energy shift. Both of these puzzles are solved by including complex saddles. We show that the convergence is dictated by the quantization of the hidden topological angle. Further, we argue that the QES systems can be linked to the exact cancellation of real and complex non-perturbative saddles to all orders in the semi-classical expansion. We also show that the entire resurgence structure remains encoded in the analytic properties of the $\zeta$-deformation, even though exactly at integer values of $\zeta$ the mechanism of resurgence is obscured by the lack of ambiguity in both the Borel sum of the perturbation theory as well as the non-perturbative contributions. In this way, all of the characteristics of resurgence remains even when its role seems to vanish, much like the lingering grin of the Cheshire Cat. We also show that the perturbative series is Self-resurgent -a feature by which there is a one-to-one relation between the early terms of the perturbative expansion and the late terms of the same expansion -which is intimately connected with the Dunne-\"{U}nsal relation. We explicitly verify that this is indeed the case.}, number={3}, journal={COMMUNICATIONS IN MATHEMATICAL PHYSICS}, author={Kozcaz, Can and Sulejmanpasic, Tin and Tanizaki, Yuya and Unsal, Mithat}, year={2018}, month={Dec}, pages={835–878} }
 @article{sulejmanpasic_shao_sandvik_unsal_2017, title={Confinement in the Bulk, Deconfinement on the Wall: Infrared Equivalence between Compactified QCD and Quantum Magnets}, volume={119}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.119.091601}, abstractNote={In a spontaneously dimerized quantum antiferromagnet, spin-1/2 excitations (spinons) are confined in pairs by strings akin to those confining quarks in non-Abelian gauge theories. The system has multiple degenerate ground states (vacua) and domain walls between regions of different vacua. For two vacua, we demonstrate that spinons on a domain wall are liberated, in a mechanism strikingly similar to domain-wall deconfinement of quarks in variants of quantum chromodynamics. This observation not only establishes a novel phenomenon in quantum magnetism, but also provides a new direct link between particle physics and condensed-matter physics. The analogy opens doors to improving our understanding of particle confinement and deconfinement by computational and experimental studies in quantum magnetism.}, number={9}, journal={PHYSICAL REVIEW LETTERS}, author={Sulejmanpasic, Tin and Shao, Hui and Sandvik, Anders W. and Unsal, Mithat}, year={2017}, month={Sep} }
 @article{sulejmanpasic_2017, title={Global Symmetries, Volume Independence, and Continuity in Quantum Field Theories}, volume={118}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.118.011601}, abstractNote={We discuss quantum field theories with global SU(N) and O(N) symmetries for which temporal direction is compactified on a circle of size L with periodicity of fields up to a global symmetry transformation, i.e., twisted boundary conditions. Such boundary conditions correspond to an insertion of the global symmetry operator in the partition function. We argue in general and prove in particular for CP(N-1) and O(N) nonlinear sigma models that large-N volume independence holds. Further we show that the CP(N-1) theory is free from the Affleck phase transition confirming the Ünsal-Dunne continuity conjecture.}, number={1}, journal={PHYSICAL REVIEW LETTERS}, author={Sulejmanpasic, Tin}, year={2017}, month={Jan} }
 @article{behtash_dunne_schaefer_sulejmanpasic_uensal_2017, title={Toward Picard-Lefschetz theory of path integrals, complex saddles and resurgence}, volume={2}, ISSN={["2380-2898"]}, url={http://inspirehep.net/record/1397667}, DOI={10.4310/amsa.2017.v2.n1.a3}, abstractNote={We show that the semi-classical analysis of generic Euclidean path integrals necessarily requires complexification of the action and measure, and consideration of complex saddle solutions.We demonstrate that complex saddle points have a natural interpretation in terms of the Picard–Lefschetz theory. Motivated in part by the semi-classical expansion of QCD with adjoint matter on $\mathbb{R}^3 \times S^1$, we study quantum-mechanical systems with bosonic and fermionic (Grassmann) degrees of freedom with harmonic degenerate minima, as well as (related) purely bosonic systems with harmonic nondegenerate minima. We find exact finite action non-BPS bounce and bion solutions to the holomorphic Newton equations. We find not only real solutions, but also complex solution with non-trivial monodromy, and finally complex multi-valued and singular solutions. Complex bions are necessary for obtaining the correct nonperturbative structure of these models. In the supersymmetric limit the complex solutions govern the ground state properties, and their contribution to the semiclassical expansion is necessary to obtain consistency with the supersymmetry algebra. The multi-valuedness of the action is either related to the hidden topological angle or to the resurgent cancellation of ambiguities. We also show that in the approximate multi-instanton description the integration over the complex quasi-zero mode thimble produces the most salient features of the exact solutions. While exact complex saddles are more difficult to construct in quantum field theory, the relation to the approximate thimble construction suggests that such solutions may be underlying some remarkable features of approximate bion saddles in quantum field theories.}, number={1}, journal={ANNALS OF MATHEMATICAL SCIENCES AND APPLICATIONS}, author={Behtash, Alireza and Dunne, Gerald V. and Schaefer, Thomas and Sulejmanpasic, Tin and Uensal, Mithat}, year={2017}, pages={95–212} }
 @article{behtash_dunne_schaefer_sulejmanpasic_uensal_2016, title={Complexified Path Integrals, Exact Saddles, and Supersymmetry}, volume={116}, ISSN={["1079-7114"]}, url={http://inspirehep.net/record/1396147}, DOI={10.1103/physrevlett.116.011601}, abstractNote={In the context of two illustrative examples from supersymmetric quantum mechanics we show that the semiclassical analysis of the path integral requires complexification of the configuration space and action, and the inclusion of complex saddle points, even when the parameters in the action are real. We find new exact complex saddles, and show that without their contribution the semiclassical expansion is in conflict with basic properties such as the positive semidefiniteness of the spectrum, as well as constraints of supersymmetry. Generic saddles are not only complex, but also possibly multivalued and even singular. This is in contrast to instanton solutions, which are real, smooth, and single valued. The multivaluedness of the action can be interpreted as a hidden topological angle, quantized in units of π in supersymmetric theories. The general ideas also apply to nonsupersymmetric theories.}, number={1}, journal={PHYSICAL REVIEW LETTERS}, author={Behtash, Alireza and Dunne, Gerald V. and Schaefer, Thomas and Sulejmanpasic, Tin and Uensal, Mithat}, year={2016}, month={Jan} }
 @article{bruckmann_gattringer_kloiber_sulejmanpasic_2016, title={Two-dimensional O(3) model at nonzero density: From dual lattice simulations to repulsive bosons}, volume={94}, ISSN={["2470-0029"]}, DOI={10.1103/physrevd.94.114503}, abstractNote={We discuss the thermodynamics of the O(3) nonlinear sigma model in $1+1$ dimensions at nonzero chemical potential (equivalent to a magnetic field). In its conventional field theory representation the model suffers from a sign problem. By dualizing the model, we are able to fully access the nonzero density regime of an asymptotically free theory with dynamical mass gap at arbitrary chemical potential values. We find a quantum phase transition at zero temperature where as a function of the chemical potential the density assumes a nonzero value. Measuring the spin stiffness we present evidence for a corresponding dynamical critical exponent $z$ close to 2. The low energy O(3) model is conjectured to be described by a massive boson triplet with repulsive interactions. We confirm the universal square-root behavior expected for such a system at low density (and temperature) and compare our data to the results of Bethe Ansatz solutions of the relativistic and nonrelativistic one-dimensional Bose gas. We also comment on a potential Berezinskii-Kosterlitz-Thouless transition at nonzero density.}, number={11}, journal={PHYSICAL REVIEW D}, author={Bruckmann, Falk and Gattringer, Christof and Kloiber, Thomas and Sulejmanpasic, Tin}, year={2016}, month={Dec} }
 @article{bruckmann_gattringer_kloiber_sulejmanpasic_2015, title={Dual lattice representations for O(N) and CP(N - 1) models with a chemical potential (vol 749, pg 495, 2015)}, volume={751}, ISSN={["1873-2445"]}, DOI={10.1016/j.physletb.2015.10.033}, abstractNote={We derive dual representations for O(N) and CP(N-1) models on the lattice. In terms of the dual variables the partition sums have only real and positive contributions also at finite chemical potential. Thus the complex action problem of the conventional formulation is overcome and using the dual variables Monte Carlo simulations are possible at arbitrary chemical potential.}, journal={PHYSICS LETTERS B}, author={Bruckmann, Falk and Gattringer, Christof and Kloiber, Thomas and Sulejmanpasic, Tin}, year={2015}, month={Dec}, pages={595–595} }
 @article{bruckmann_gattringer_kloiber_sulejmanpasic_2015, title={Dual lattice representations for O(N) and CP(N-1) models with a chemical potential}, volume={749}, ISSN={["1873-2445"]}, DOI={10.1016/j.physletb.2015.08.015}, abstractNote={We derive dual representations for O(N) and CP(N−1) models on the lattice. In terms of the dual variables the partition sums have only real and positive contributions also at finite chemical potential. Thus the complex action problem of the conventional formulation is overcome and using the dual variables Monte Carlo simulations are possible at arbitrary chemical potential.}, journal={PHYSICS LETTERS B}, author={Bruckmann, Falk and Gattringer, Christof and Kloiber, Thomas and Sulejmanpasic, Tin}, year={2015}, month={Oct}, pages={495–501} }
 @article{bruckmann_gattringer_kloiber_sulejmanpasic_2015, title={Grand Canonical Ensembles, Multiparticle Wave Functions, Scattering Data, and Lattice Field Theories}, volume={115}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.115.231601}, abstractNote={We show that information about scattering data of a quantum field theory can be obtained from studying the system at finite density and low temperatures. In particular we consider models formulated on the lattice that can be exactly dualized to theories of conserved charge fluxes on lattice links. Apart from eliminating the complex action problem at nonzero chemical potential μ, these dualizations allow for a particle world line interpretation of the dual fluxes from which one can extract data about the two-particle wave function. As an example we perform dual Monte Carlo simulations of the two-dimensional O(3) model at nonzero μ and finite volume, whose nonperturbative spectrum consists of a massive triplet of particles. At nonzero μ particles are induced in the system, which at sufficiently low temperature give rise to sectors of fixed particle number. We show that the scattering phase shifts can be obtained either from the critical chemical potential values separating the sectors or directly from the wave function in the two-particle sector. We find that both methods give excellent agreement with the exact result. We discuss the applicability and generality of the new approaches.}, number={23}, journal={PHYSICAL REVIEW LETTERS}, author={Bruckmann, Falk and Gattringer, Christof and Kloiber, Thomas and Sulejmanpasic, Tin}, year={2015}, month={Dec} }
 @article{behtash_sulejmanpasic_schaefer_uensal_2015, title={Hidden Topological Angles in Path Integrals}, volume={115}, ISSN={["1079-7114"]}, url={http://inspirehep.net/record/1346264}, DOI={10.1103/physrevlett.115.041601}, abstractNote={We demonstrate the existence of hidden topological angles (HTAs) in a large class of quantum field theories and quantum mechanical systems. HTAs are distinct from theta-parameters in the lagrangian. They arise as invariant angle associated with saddle points of the complexified path integral and their descent manifolds (Lefschetz thimbles). Physical effects of HTAs become most transparent upon analytic continuation in n f to non-integer number of flavors, reducing in the integer n f limit to a Z2 valued phase difference between dominant saddles. In N = 1 super Yang-Mills theory we demonstrate the microscopic mechanism for the vanishing of the gluon condensate. The same effect leads to an anomalously small condensate in a QCD-like SU(N) gauge theory with fermions in the two-index representation. The basic phenomenon is that, contrary to folklore, the gluon condensate can receive both positive and negative contributions in a semi-classical expansion. In quantum mechanics, a HTA leads to a difference in semi-classical expansion of integer and half-integer spin particles.}, number={4}, journal={PHYSICAL REVIEW LETTERS}, author={Behtash, Alireza and Sulejmanpasic, Tin and Schaefer, Thomas and Uensal, Mithat}, year={2015}, month={Jul} }
 @article{anber_poppitz_sulejmanpasic_2015, title={Strings from domain walls in supersymmetric Yang-Mills theory and adjoint QCD}, volume={92}, ISSN={["1550-2368"]}, DOI={10.1103/physrevd.92.021701}, abstractNote={We study strings between static quarks in QCD with nf adjoint fermions, including N = 1 supersymmetric Yang-Mills (SYM), in the calculable regime on R-3 x S-L(1), which shares many features with the XY-spin model. We find that they have many qualitatively new features not previously known. The difference from other realizations of Abelian confinement is due to the composite nature of magnetic bions, whose Dirac quantum with fundamental quarks is two, and to the unbroken part of the Weyl group. In particular we show that strings are composed of two domain walls, that quarks are not confined on domain walls, that strings can end on domain walls, and that "Y" or "Delta" baryons can form. By similar argumentation, liberation of vortices on domain walls in the condensed matter counterparts may have important implications in the physics of transport. In the gauge theory we briefly discuss the lightest modes of strings and the decompactification limit.}, number={2}, journal={PHYSICAL REVIEW D}, author={Anber, Mohamed M. and Poppitz, Erich and Sulejmanpasic, Tin}, year={2015}, month={Jul} }
 @article{behtash_poppitz_sulejmanpasic_ünsal_2015, title={The curious incident of multi-instantons and the necessity of Lefschetz thimbles}, volume={2015}, ISSN={1029-8479}, url={http://dx.doi.org/10.1007/JHEP11(2015)175}, DOI={10.1007/jhep11(2015)175}, abstractNote={We show that compatibility of supersymmetry with exact semi-classics demands that in calculating multi-instanton amplitudes, the "separation" quasi-zeromode must be complexified and the integration cycles must be found by using complex gradient flow (or Picard-Lefschetz equations.) As a non-trivial application, we study $$ \mathcal{N}=2 $$ extended supersymmetric quantum mechanics. Even though in this case supersymmetry is unbroken, the instanton-anti-instanton amplitude (naively calculated) seems to contribute to the ground state energy. We show, however, that the instanton-anti-instanton event consists of two parts: a fermion-correlated and a scalar-correlated event. Although both of these contributions are naively of the same sign and the latter is superficially higher order in the perturbative coupling, we show that the two contributions exactly cancel when they are evaluated on Lefschetz thimbles due to their relative Hidden Topological Angles (HTAs). This gives strong evidence that the semi-classical expansion using Lefschetz thimbles is not only a meaningful prescription for higher order semi-classics, but a necessary one. This deduction seems to be universal and applicable to both supersymmetric and non-supersymmetric theories. In conclusion we speculate that similar conspiracies are responsible for the non-formation of certain molecular contributions in theories where instantons have more than two fermionic zeromodes and do not contribute to the superpotential.}, number={11}, journal={Journal of High Energy Physics}, publisher={Springer Nature}, author={Behtash, Alireza and Poppitz, Erich and Sulejmanpasic, Tin and Ünsal, Mithat}, year={2015}, month={Nov}, pages={175} }
 @article{anber_sulejmanpasic_2015, title={The renormalon diagram in gauge theories on R-3 x S-1}, ISSN={["1029-8479"]}, DOI={10.1007/jhep01(2015)139}, abstractNote={We analyze the renormalon diagram of gauge theories on $$ {\mathrm{\mathbb{R}}}^3\times {\mathbb{S}}^1 $$ . In particular, we perform exact one loop calculations for the vacuum polarization in QCD with adjoint matter and observe that all infrared logarithms, as functions of the external momentum, cancel between the vacuum part and finite volume part, which eliminates the IR renormalon problem. We argue that the singularities in the Borel plane, arising from the topological neutral bions, are not associated with the renormalon diagram, but with the proliferation of the Feynman diagrams. As a byproduct, we obtain, for the first time, an exact one-loop result of the vacuum polarization which can be adapted to the case of thermal compactification of QCD.}, number={1}, journal={JOURNAL OF HIGH ENERGY PHYSICS}, author={Anber, Mohamed M. and Sulejmanpasic, Tin}, year={2015}, month={Jan} }