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Michael G. Endres

Publications and source records attributed to Michael G. Endres.

27 records · Page 2Linked to original sources
arXiv2011

A new approach for studying large numbers of fermions in the unitary regime

A novel lattice approach is presented for studying systems comprising a large number of interacting nonrelativistic fermions. The construction is ideally suited for numerical study of fermions near unitarity--a strongly coupled regime corresponding to the two-particle s-wave scattering phase shift delta_0 = pi/2. Such systems may be achieved experimentally with trapped atoms, and provide a starting point for an effective field theory description of nuclear physics. We discuss the construction of our lattice theory, which allows us to study systems of up to (but by no means limited to) 38 fermions with high accuracy and modest computational resources, and offer an overview of several applications of the technique. A more detailed discussion of applications and simulation results will be described in companion proceedings by A. N. N. and J-W. L.

hep-lat↗
arXiv2010

Lattice study of trapped fermions at unitarity

We present a lattice study of up to N=20 unitary fermions confined to a harmonic trap. Our preliminary results show better than 1% agreement with high precision solutions to the many-body Schrodinger equation for up to N=6. We are able to make predictions for larger N which were inaccessible by the Hamiltonian approach due to computational limitations. Harmonic traps are used experimentally to study cold atoms tuned to a Feshbach resonance. We show that they also provide certain benefits to numerical studies of many-body correlators on the lattice. In particular, we anticipate that the methods described here could be used for studying nuclear physics.

hep-lat↗
arXiv2010

Lattice calculation for unitary fermions in a finite box

A fundamental constant in systems of unitary fermions is the so-called Bertsch parameter, the ratio of the ground state energy for spin paired unitary fermions to that for free fermions at the same density. I discuss how we computed this parameter as well as the pairing gap using a recently developed lattice construction for unitary fermions, by measuring correlation functions for up to 38 fermions in a finite box. Our calculation illustrates interesting issues facing the study of many-body states on the lattice, which may eventually be confronted in QCD calculations as well.

hep-lat↗
arXiv2009

N=1 super Yang-Mills on the lattice

We present results from a numerical study of N=1 supersymmetric Yang-Mills theory using domain wall fermions. A set of dynamical simulations were performed for the gauge group SU(2) using the Wilson gauge action on 8^3x8 and 16^3x32 lattices. We considered a range of gluino masses (i.e., fifth dimension extents L_s=16-28 and input gluino mass values m_f=0.01-0.04) in order to perform chiral limit extrapolations of physical quantities. In these proceedings, we summarize our findings from a study of the Dirac spectrum and present new results for the topological charge on beta=2.3, 2.353 and 2.4 ensembles.

hep-lat↗
arXiv2009

Dynamical simulation of N=1 supersymmetric Yang-Mills theory with domain wall fermions

We present results from a numerical study of N=1 supersymmetric Yang-Mills theory using domain wall fermions. In this particular lattice formulation of the theory, supersymmetry is expected to emerge accidentally in the continuum and chiral limits without any fine-tuning of operators. Dynamical simulations were performed for the gauge group SU(2) on 8^3x8 and 16^3x32 lattice space-time volumes and at three different values of the coupling: beta = 2.3, 2.353 and 2.4. Results from this study include measurements of the static potential, residual mass, and a chirally extrapolated value for the gluino condensate at beta=2.3. In addition to these, we study the low lying eigenvalues and eigenvectors of the five dimensional Hermitian domain-wall fermion Dirac operator and present evidence that, for the choice of parameters under investigation, features of the spectrum appear qualitatively consistent with strong coupling and the presence of a large residual mass. From the five dimensional eigenvalues we explore the possibility of using the Banks-Casher relation to determine an independent value for the gluino condensate in the chiral limit.

hep-lat↗
arXiv2008

Numerical simulation of N=1 supersymmetric Yang-Mills theory

We present results from a lattice study of SU(2) color, N=1 supersymmetric Yang-Mills theory using domain wall fermions. Supersymmetry in this particular lattice formulation is expected to emerge in the continuum and chiral limits without any fine-tuning of operators. Preliminary results for the static quark potential, residual mass, chiral condensate and spectrum--a potential indicator of supersymmetry restoration--are presented and discussed.

hep-lat↗
arXiv2007

Method for simulating O(N) lattice models at finite density

We present a method for simulating relativistic and nonrelativistic scalar field theories at finite density, with matter transforming in the fundamental representation of the global symmetry group O(N). The method avoids the problem of complex probability weights which is present in conventional path integral Monte Carlo algorithms. To verify our approach, we simulate the free and interacting relativistic U(1)=O(2) theory in 2+1 dimensions. We compute the two-point correlation function and charge density as a function of chemical potential in the free theory. At weak phi^4 coupling and zero temperature we map the m^2-mu phase diagram and compare our numerical results with perturbative calculations. Finally, we compute properties of theT-mu phase diagram in the vicinity of the phase transition and at bare self-couplings large compared to the temperature and chemical potential.

hep-lat↗
arXiv2006

Avoiding the boson sign problem at finite chemical potential

The usual path integral formulation for scalar particles at finite density involves a sign problem, making numerical simulation impractical. We present alternative methods free of this difficulty. We apply these approaches to phi^4 theory in 2+1 dimensions, presenting preliminary numerical results for physical quantities in the vicinity of the phase transition in the T-mu plane.

hep-lat↗