@article{nguyen_singh_2023, title={Lattice regularizations of theta vacua: Anomalies and qubit models}, volume={107}, ISSN={["2470-0029"]}, DOI={10.1103/PhysRevD.107.014507}, abstractNote={Anomalies are a powerful way to gain insight into possible lattice regularizations of a quantum field theory. In this work, we argue that the continuum anomaly for a given symmetry can be matched by a manifestly-symmetric, local, lattice regularization in the same spacetime dimensionality only if (i) the symmetry action is offsite, or (ii) if the continuum anomaly is reproduced exactly on the lattice. We consider lattice regularizations of a class of prototype models of QCD: the (1+1)-dimensional asymptotically-free Grassmannian nonlinear sigma models (NLSMs) with a $\theta$ term. Using the Grassmannian NLSMs as a case study, we provide examples of lattice regularizations in which both possibilities are realized. For possibility (i), we argue that Grassmannian NLSMs can be obtained from $\mathrm{SU}(N)$ antiferromagnets with a well-defined continuum limit, reproducing both the infrared physics of $\theta$ vacua and the ultraviolet physics of asymptotic freedom. These results enable the application of new classical algorithms to lattice Monte Carlo studies of these quantum field theories, and provide a viable realization suited for their quantum simulation. On the other hand, we show that, perhaps surprisingly, the conventional lattice regularization of $\theta$ vacua due to Berg and L\"uscher reproduces the anomaly exactly on the lattice, providing a realization of the second possibility.}, number={1}, journal={PHYSICAL REVIEW D}, author={Nguyen, Mendel and Singh, Hersh}, year={2023}, month={Jan} }
 @article{nguyen_tanizaki_unsal_2023, title={Study of gapped phases of 4d gauge theories using temporal gauging of the Z(N) 1-form symmetry}, ISSN={["1029-8479"]}, DOI={10.1007/JHEP08(2023)013}, abstractNote={Abstract
                     }, number={8}, journal={JOURNAL OF HIGH ENERGY PHYSICS}, author={Nguyen, Mendel and Tanizaki, Yuya and Unsal, Mithat}, year={2023}, month={Aug} }
 @article{nguyen_tanizaki_unsal_2023, title={Winding ? and destructive interference of instantons}, ISSN={["1029-8479"]}, DOI={10.1007/JHEP09(2023)033}, abstractNote={A bstract While the θ dependence of field theories is 2 π periodic, the ground-state wavefunctions at θ and θ + 2 π often belong to different classes of symmetry-protected topological states. When this is the case, a continuous change of the θ parameter can introduce an interface that supports a nontrivial field theory localized on the wall. We consider the 2d ℂ P N −1 sigma model as an example and construct a weak-coupling setup of this interface theory by considering the small S 1 compactification with nonzero winding θ parameter and a suitable symmetry-twisted boundary condition. This system has N classical vacua connected by fractional instantons, but the anomaly constraint tells us that the fractional-instanton amplitudes should vanish completely to have N -fold degeneracy at the quantum level. We show how this happens in this purely bosonic system, uncovering that the integration over the zero modes annihilates the fractional instanton amplitudes, in sharp contrast to what happens when the θ angle is constant. Moreover, we provide another explanation of this selection rule by showing that the N perturbative vacua acquire different charges under the global symmetry with the activation of the winding θ angle. We also demonstrate a similar destructive interference between instanton effects in the ℂ P N −1 quantum mechanics with the Berry phase.}, number={9}, journal={JOURNAL OF HIGH ENERGY PHYSICS}, author={Nguyen, Mendel and Tanizaki, Yuya and Unsal, Mithat}, year={2023}, month={Sep} }
 @article{nguyen_tanizaki_unsal_2021, title={Noninvertible 1-form symmetry and Casimir scaling in 2D Yang-Mills theory}, volume={104}, ISSN={["2470-0029"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85114421307&partnerID=MN8TOARS}, DOI={10.1103/PhysRevD.104.065003}, abstractNote={Pure Yang-Mills theory in 2 spacetime dimensions shows exact Casimir scaling. Thus there are infinitely many string tensions, and this has been understood as a result of non-propagating gluons in 2 dimensions. From ordinary symmetry considerations, however, this richness in the spectrum of string tensions seems mysterious. Conventional wisdom has it that it is the center symmetry that classifies string tensions, but being finite it cannot explain infinitely many confining strings. In this note, we resolve this discrepancy between dynamics and kinematics by pointing out the existence of a non-invertible 1-form symmetry, which is able to distinguish Wilson loops in different representations. We speculate on possible implications for Yang-Mills theories in 3 and 4 dimensions.}, number={6}, journal={PHYSICAL REVIEW D}, author={Nguyen, Mendel and Tanizaki, Yuya and Unsal, Mithat}, year={2021}, month={Sep} }
 @article{nguyen_tanizaki_unsal_2021, title={Semi-Abelian gauge theories, non-invertible symmetries, and string tensions beyond N-ality}, volume={03}, ISSN={["1029-8479"]}, url={http://inspirehep.net/record/1839639}, DOI={10.1007/JHEP03(2021)238}, abstractNote={Abstract
                     }, number={3}, journal={JOURNAL OF HIGH ENERGY PHYSICS}, author={Nguyen, Mendel and Tanizaki, Yuya and Unsal, Mithat}, year={2021}, month={Mar} }