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7.0

Jun 29, 2018
06/18

by
Derar Altarawneh; Michael Engelhardt; Roman Höllwieser

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A picture of confinement in QCD based on a condensate of thick vortices with fluxes in the center of the gauge group (center vortices) is studied. Previous concrete model realizations of this picture utilized a hypercubic space-time scaffolding, which, together with many advantages, also has some disadvantages, e.g., in the treatment of vortex topological charge. In the present work, we explore a center vortex model which does not rely on such a scaffolding. Vortices are represented by closed...

Topics: High Energy Physics - Theory, High Energy Physics - Lattice

Source: http://arxiv.org/abs/1606.07115

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Jun 28, 2018
06/18

by
Derar Altarawneh; Roman Höllwieser; Michael Engelhardt

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We present static meson-meson and baryon--anti-baryon potentials in Z(2) and Z(3) random center vortex models for the infrared sector of Yang-Mills theory, i.e., hypercubic lattice models of random vortex world-surfaces. In particular, we calculate Polyakov loop correlators of two static mesons resp. (anti-)baryons in a center vortex background and observe that their expectation values follow the minimal area law and show bond rearrangement behavior. The static meson-meson and...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1508.07596

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3.0

Jun 29, 2018
06/18

by
Jeff Greensite; Roman Höllwieser

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The method of relative weights, coupled with mean field theory, is applied to the problem of simulating gauge theories with dynamical staggered fermions at finite densities. We present initial results and discuss issues so far encountered.

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1610.06239

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3.0

Jun 30, 2018
06/18

by
Jeff Greensite; Roman Höllwieser

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We consider "double-winding" Wilson loops in SU(2) gauge theory. These are contours which wind once around a loop $C_1$ and once around a loop $C_2$, where the two co-planar loops share one point in common, and where $C_1$ lies entirely in (or is displaced slightly from) the minimal area of $C_2$. We discuss the expectation value of such double-winding loops in abelian confinement pictures, where the spatial distribution of confining abelian fields is controlled by either a monopole...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1411.5091

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Sep 22, 2013
09/13

by
Manfried Faber; Jeff Greensite; Urs M. Heller; Roman Höllwieser; Štefan Olejník

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We study correlations between center vortices and the low-lying eigenmodes of the Dirac operator, in both the overlap and asqtad formulations. In particular we address a puzzle raised some years ago by Gattnar et al. [Nucl. Phys. B 716, 105 (2005)], who noted that the low-lying Dirac eigenmodes required for chiral symmetry breaking do not appear to be present in center-projected configurations. We show that the low-lying modes are in fact present in the staggered (asqtad) formulation, but not...

Source: http://arxiv.org/abs/0805.1846v2

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13

Jun 28, 2018
06/18

by
Roman Höllwieser; Derar Altarawneh

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We present meson-meson (Wilson loop) correlators in Z(2) center vortex models for the infrared sector of Yang-Mills theory, i.e., a hypercubic lattice model of random vortex surfaces and a continuous 2+1 dimensional model of random vortex lines. In particular we calculate quadratic and circular Wilson loop correlators in the two models respectively and observe that their expectation values follow the area law and show string breaking behavior. Further we calculate the catenary solution for the...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1509.00145

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3.0

Jun 30, 2018
06/18

by
Roman Höllwieser; Derar Altarawneh; Michael Engelhardt

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We present a model of center vortices, represented by closed random lines in continuous 2+1- dimensional space- time. These random lines are modeled as being piece-wise linear and an ensemble is generated by Monte Carlo methods. The physical space in which the vortex lines are defined is a cuboid with periodic boundary conditions. Besides moving, growing and shrinking of the vortex configuration, also reconnections are allowed. Our ensemble therefore contains not a fixed, but a variable number...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1411.7089

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5.0

Jun 29, 2018
06/18

by
Roman Höllwieser; Jeff Greensite

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We derive effective Polyakov line actions for SU(3) gauge theories with staggered dynamical fermions, for a small sample of lattice couplings, lattice actions, and lattice extensions in the time direction. The derivation is via the method of relative weights, and the theories are solved at finite chemical potential by mean field theory. We find in some instances that the long-range couplings in the effective action are very important to the phase structure, and that these couplings are...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1603.09654

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Jun 29, 2018
06/18

by
Roman Höllwieser; Jeff Greensite

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We extract an effective Polyakov line action from an underlying SU(3) lattice gauge theory with dynamical fermions via the relative weights method. The center-symmetry breaking terms in the effective theory are fit to a form suggested by effective action of heavy-dense quarks, and the effective action is solved at finite chemical potential by a mean field approach. We show results for a small sample of lattice couplings, lattice actions, and lattice extensions in the time direction. We find in...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1611.03973

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4.0

Jun 28, 2018
06/18

by
Roman Höllwieser; Jeff Greensite

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We apply the relative weights method to extract an effective Polyakov line action, at finite chemical potential, from an underlying $SU(3)$ lattice gauge theory with dynamical fermions. The center-symmetry breaking terms in the effective theory are fit to a form suggested by the hopping-parameter expansion, and the effective action is solved at finite chemical potential by a mean field approach. We present preliminary results for one-link staggered fermions with mass $ma=1.0$ and Wilson gauge...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1510.03824

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Jun 27, 2018
06/18

by
Roman Höllwieser; Jeff Greensite

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We present evidence that the center vortex model of confinement is more consistent with lattice results than other currently available models. In particular we show that Abelian field distributions predicted by monopole plasma, caloron gas or dual superconductor models cannot reproduce the area-law falloff of double winding Wilson loops in full $SU(2)$ and center vortex only gauge fields.

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1504.07663

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3.0

Jun 30, 2018
06/18

by
Roman Höllwieser; Manfried Faber; Thomas Schweigler; Urs M. Heller

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We analyze the creation of near-zero modes from would-be zero modes of various topological charge contributions from classical center vortices in SU(2) lattice gauge theory. We show that colorful spherical vortex and instanton configurations have very similar Dirac eigenmodes and also vortex intersections are able to give rise to a finite density of near-zero modes, leading to chiral symmetry breaking via the Banks-Casher formula. We discuss the influence of the magnetic vortex fluxes on quarks...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1410.2333

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Sep 22, 2013
09/13

by
Roman Höllwieser; Manfried Faber; Urs M. Heller

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Intersections of thick, plane SU(2) center vortices are characterized by the topological charge |Q|=1/2. We compare such intersections with the distribution of zeromodes of the Dirac operator in the fundamental and adjoint representation using both the overlap and asqtad staggered fermion formulations in SU(2) lattice gauge theory. We analyze configurations with four intersections and find that the probability density distribution of fundamental zeromodes in the intersection plane differs...

Source: http://arxiv.org/abs/1103.2669v4

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Jul 19, 2013
07/13

by
Roman Höllwieser; Manfried Faber; Urs M. Heller

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We study topological properties of classical spherical center vortices with the low-lying eigenmodes of the Dirac operator in the fundamental and adjoint representations using both the overlap and asqtad staggered fermion formulations. In particular we address the puzzle raised in a previous work of our group [Phys.\ Rev.\ D 77, 14515 (2008)], where we found a violation of the lattice index theorem with the overlap Dirac operator in the fundamental representation even for "admissible"...

Source: http://arxiv.org/abs/1005.1015v2

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Jun 27, 2018
06/18

by
Roman Höllwieser; Michael Engelhardt

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We present a method to smear (center projected) $Z(2)$ vortices in lattice gauge configurations such as to embed vortex physics into a full $SU(2)$ gauge configuration framework. In particular, we address the problem that using $Z(2)$ configurations in conjunction with overlap (or chirally improved) fermions is problematic due to their lack of smoothness. Our method allows us to regain this smoothness and simultaneously maintain the center vortex structure. We verify our method with various...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1503.00016

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Jun 30, 2018
06/18

by
Roman Höllwieser; Michael Engelhardt

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We smear Z(2) center vortices in lattice gauge configurations such as to recover thick vortices with full SU(2) Yang-Mills information. In particular, we address the problem that using Z(2) configurations in conjunction with overlap (or chirally improved) fermions is problematic due to their lack of smoothness. Our method allows us to regain this smoothness and simultaneously maintain the center vortex structure. We verify our method with various gluonic and fermionic observables and find good...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1411.7097

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109

Jul 20, 2013
07/13

by
Roman Höllwieser; Thomas Schweigler; Manfried Faber; Urs M. Heller

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We investigate the chiral properties of near-zero modes for thick classical center vortices. In particular we analyze the creation of near-zero modes from would-be zero modes of various topological charge contributions from center vortices. We show that colorful spherical vortex and instanton ensembles have very similar Dirac eigenmodes and also vortex intersections are able to give rise to a finite density of near-zero modes, leading to chiral symmetry breaking via the Banks-Casher formula. We...

Source: http://arxiv.org/abs/1304.1277v1

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Jun 29, 2018
06/18

by
Tareq Alhalholy; Roman Höllwieser

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Using the relativistic Eikonal approximation, we study the one and two photon exchange amplitudes in elastic electron-nucleon scattering for the case of transversely polarized nucleons with unpolarized electrons beam. In our approach, we utilize the convolution theory of Fourier transforms and the transverse charge density in transverse momentum space to evaluate the one and two photon exchange Eikonal amplitudes. The results obtained for the $2\gamma$ amplitude in impact parameter space are...

Topic: High Energy Physics - Phenomenology

Source: http://arxiv.org/abs/1605.05202

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Sep 23, 2013
09/13

by
Thomas Schweigler; Roman Höllwieser; Manfried Faber; Urs M. Heller

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The spherical vortex as introduced in [Phys. Rev. D77, 014515 (2008)] is generalized. A continuum form of the spherical vortex is derived and investigated in detail. The discrepancy between the gluonic lattice topological charge and the index of the lattice Dirac operator described in previous papers is identified as a discretization effect. The importance of the investigations for Monte Carlo configurations is discussed.

Source: http://arxiv.org/abs/1212.3737v2