351 research outputs found

### New algorithms and new results for strong coupling LQCD

We present and compare new types of algorithms for lattice QCD with staggered fermions in the limit
of infinite gauge coupling. These algorithms are formulated on a discrete spatial lattice but with continuous
Euclidean time. They make use of the exact Hamiltonian, with the inverse temperature beta
as the only input parameter. This formulation turns out to be analogous to that of a quantum spin
system. The sign problem is completely absent, at zero and non-zero baryon density. We compare
the performance of a continuous-time worm algorithm and of a Stochastic Series Expansion algorithm
(SSE), which operates on equivalence classes of time-ordered interactions. Finally, we apply the SSE
algorithm to a first exploratory study of two-flavor strong coupling lattice QCD, which is manageable
in the Hamiltonian formulation because the sign problem can be controlled

### Dual Formulation and Phase Diagram of Lattice QCD in the Strong Coupling Regime

We present the computation of invariants that arise in the strong coupling
expansion of lattice QCD. These invariants are needed for Monte Carlo
simulations of Lattice QCD with staggered fermions in a dual, color singlet
representation. This formulation is in particular useful to tame the finite
density sign problem. The gauge integrals in this limiting case
$\beta\rightarrow 0$ are well known, but the gauge integrals needed to study
the gauge corrections are more involved. We discuss a method to evaluate such
integrals.
The phase boundary of lattice QCD for staggered fermions in the $\mu_B-T$
plane has been established in the strong coupling limit. We present numerical
simulations away from the strong coupling limit, taking into account the higher
order gauge corrections via plaquette occupation numbers. This allows to study
the nuclear and chiral transition as a function of $\beta$.Comment: 16 pages, 10 figures, Proceedings of the 35th International Symposium
on Lattice Field Theory, Granada, Spai

### A surprise with many-flavor staggered fermions in the strong coupling limit

It is widely believed that chiral symmetry is spontaneously broken at zero temperature in the strong coupling limit of staggered fermions, for any number of colors and flavors. Using Monte Carlo simulations, we show that this conventional wisdom, based on a mean-field analysis, is wrong. For sufficiently many fundamental flavors, chiral symmetry is restored via a bulk, first-order transition. This chirally symmetric phase appears to be analytically connected with the expected conformal window of manyflavor continuum QCD. We perform simulations in the chirally symmetric phase at zero quark mass for various system sizes L, and measure the torelon mass and the Dirac spectrum. We find that all observables scale with L, which is hence the only infrared length scale. Thus, the strong-coupling chirally restored phase appears as a convenient laboratory to study IR-conformality. Finally, we present a conjecture for the phase diagram of lattice QCD as a function of the bare coupling and the number of quark flavors

### QCD phase diagram from the lattice at strong coupling

The phase diagram of lattice QCD in the strong coupling limit can be measured
in the full $\mu$-$T$ plane, also in the chiral limit. In particular, the phase
diagram in the chiral limit features a tricritical point at some $(\mu_c,T_c)$.
This point may be related to the critical end point expected in the QCD phase
diagram. We discuss the gauge corrections to the phase diagram at strong
coupling and compare our findings with various possible scenarios in continuum
QCD. We comment on the possibility that the tricritical point at strong
coupling is connected to the tricritical point in the continuum, massless QCD.Comment: 9 pages, 5 figures. Presented at CPOD 2014 (Critical Point and Onset
of Deconfinement), November 17-21, 2014, Bielefeld, German

### The Phase Diagram of Strong Coupling QCD including Gauge Corrections

The strong coupling limit of lattice QCD with staggered fermions has been
studied for decades, both via Monte Carlo and via mean field theory. In this
model, the finite density sign problem can be made mild and the full phase
diagram can be obtained, even in the chiral limit. It is however desirable to
understand the effect of a finite lattice gauge coupling $\beta$ on the phase
diagram in the $\mu-T$ plane in order to understand how it evolves into the
phase diagram of continuum QCD. Here we discuss how to construct a partition
function for non-zero lattice coupling, exact to $\mathcal{O}(\beta)$, and
present corresponding Monte Carlo results, in particular for corrections to the
chiral susceptibility and to the phase diagram.Comment: 7 pages, 5 figures. Proceedings of the 31st International Symposium
on Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz,
Germany - Figure showing phase diagram dependence on beta correcte

### The lattice QCD phase diagram in and away from the strong coupling limit

We study lattice QCD with four flavors of staggered quarks. In the limit of
infinite gauge coupling, "dual" variables can be introduced, which render the
finite-density sign problem mild and allow a full determination of the $\mu-T$
phase diagram by Monte Carlo simulations, also in the chiral limit. However,
the continuum limit coincides with the weak coupling limit. We propose a
strong-coupling expansion approach towards the continuum limit. We show first
results, including the phase diagram and its chiral critical point, from this
expansion truncated to next-to-leading order.Comment: 5 pages, 7 figures; submitted to Phys. Rev. Let

### Hinweise zur qualitätsgerechten Planung und Ausführung von Estrich- und Fußbodenkonstruktionen im Wohn-, Gesellschafts- und Industriebau

Fußbodenkonstruktionen als Stiefkind der Planung und Ausführung? Bei der Ausführung von Fußböden gibt es viele Fehlerquellen. Ein umfassendes Kompendium mit Hinweisen aus der Praxis für die Planung und Ausführung von Fußböden ist im Jahr 2000 mit dem FUSSBODENATLAS erschienen; die vorliegende Veröffentlichung wurde in Auszügen diesem Werk entnommen

### Towards a Dual Representation of Lattice QCD

Our knowledge about the QCD phase diagram at finite baryon chemical potential
$\mu_{B}$ is limited by the well known sign problem. The path integral measure,
in the standard determinantal approach, becomes complex at finite $\mu_{B}$ so
that standard Monte Carlo techniques cannot be directly applied. As the sign
problem is representation dependent, by a suitable choice of the fundamental
degrees of freedom that parameterize the partition function, it can get mild
enough so that reweighting techniques can be used. A successful formulation,
capable to tame the sign problem, is known since decades in the limiting case
$\beta\to 0$, where performing the gauge integration first, gives rise to a
dual formulation in terms of color singlets (MDP formulation). Going beyond the
strong coupling limit represents a serious challenge as the gauge integrals
involved in the computation are only partially known analytically and become
strongly coupled for $\beta>0$. We will present explict formulae for all the
integral relevant for ${\rm SU}(N)$ gauge theories discretised \`a la Wilson,
and will discuss how they can be used to obtain a positive dual formulation,
valid for all $\beta$, for pure Yang Mills theory.Comment: 7 pages, 1 figure, proceedings to talk presented at 36th annual
International Symposium on Lattice Field Theory, 22-28 July 2018, East
Lansing, MI, US

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