tag:blogger.com,1999:blog-79243486303643567332017-02-08T20:50:04.525-08:00High Energy Physics - LatticeSite for <a href="http://communitypeerreview.blogspot.com/">Community Peer Review</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.comBlogger1635125tag:blogger.com,1999:blog-7924348630364356733.post-73453963708842847362013-08-05T00:02:00.003-07:002013-08-05T00:02:11.834-07:001308.0343 (Emil J. Bergholtz et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0343">Topological Flat Band Models and Fractional Chern Insulators</a> [<a href="http://arxiv.org/pdf/1308.0343">PDF</a>]</h2>Emil J. Bergholtz, Zhao Liu<a name='more'></a><blockquote class="abstract">Topological insulators are accompanied by exotic edge states that are protected by a bulk single-particle band gap once the filled bands are characterized by non-trivial topological invariants. Interactions can have profound effects and lead to entirely new insulating phases, with an altogether much richer and less explored phenomenology, as is particularly clear in the case of partial filling of weakly dispersive bands. Most saliently, lattice generalizations of fractional quantum Hall states, dubbed fractional Chern insulators, have recently been predicted to be stabilized by interactions within nearly dispersionless bands with non-zero Chern number, $C$. Contrary to their continuum analogues, these states do not require an external magnetic field and may potentially persist at high temperatures, which make these systems very interesting in the context of applications such as topological quantum computation. This review recapitulates the basics of tight-binding models hosting nearly flat bands with non-trivial topology, $C\neq 0$, and summarizes the present understanding of interactions and strongly correlated phases within these bands. Emphasis is put on the analogy with continuum Landau level physics, as well as qualitatively new, lattice specific, aspects including Berry curvature fluctuations, competing instabilities as well as novel collective states of matter emerging in bands with $|C|>1$. Possible experimental realizations, including oxide interfaces and cold atom implementations as well as generalizations to flat bands characterized by other topological invariants are also discussed.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0343">http://arxiv.org/abs/1308.0343</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-65082201307889238292013-08-05T00:02:00.001-07:002013-08-05T00:02:10.897-07:001308.0528 (K. Stannigel et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0528">Constrained dynamics via the Zeno effect in quantum simulation:<br /> Implementing non-Abelian lattice gauge theories with cold atoms</a> [<a href="http://arxiv.org/pdf/1308.0528">PDF</a>]</h2>K. Stannigel, P. Hauke, D. Marcos, M. Hafezi, S. Diehl, M. Dalmonte, P. Zoller<a name='more'></a><blockquote class="abstract">We show how engineered classical noise can be used to generate constrained Hamiltonian dynamics in atomic quantum simulators of many-body systems, taking advantage of the continuous Zeno effect. After discussing the general theoretical framework, we focus on applications in the context of lattice gauge theories, where imposing exotic, quasi-local constraints is usually challenging. We demonstrate the effectiveness of the scheme for both Abelian and non-Abelian gauge theories, and discuss how engineering dissipative constraints substitutes complicated, non-local interaction patterns by global coupling to laser fields.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0528">http://arxiv.org/abs/1308.0528</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-86587907323436779452013-08-04T00:03:00.011-07:002013-08-04T00:03:21.552-07:001308.0020 (Ariel R. Zhitnitsky)<h2 class="title"><a href="http://arxiv.org/abs/1308.0020">Conformal window in QCD for large numbers of colours and flavours</a> [<a href="http://arxiv.org/pdf/1308.0020">PDF</a>]</h2>Ariel R. Zhitnitsky<a name='more'></a><blockquote class="abstract">We conjecture that the phase transitions in QCD at large number of colours $N\gg 1$ is triggered by the drastic change in $\theta$ behaviour. The conjecture is motivated by the holographic model of QCD where confinement -deconfinement phase transition indeed happens precisely at temperature $T=T_c$ where $\theta$ dependence experiences a sudden change in behaviour: from $N^2\cos(\theta/N)$ at $T<T_c$ to $\cos\theta\exp(-N)$ at $T>T_c$. This conjecture is also supported by recent lattice studies. We employ this conjecture to study a possible phase transition as a function of $\kappa\equiv N_f/N$ from confinement to conformal phase in the Veneziano limit $N_f\sim N$ when number of flavours and colours are large, but the ratio $\kappa$ is finite. Technically, we consider an operator which gets its expectation value solely from nonperturbative instaton effects. When $\kappa$ exceeds some critical value $\kappa> \kappa_c$ the integral over instanton size is dominated by small-size instatons, making the instanton computations reliable with expected $\exp(-N)$ behaviour. However, when $\kappa<\kappa_c$, the integral over instaton size is dominated by large-size instantons, and the instanton expansion breaks down. This regime with $\kappa<\kappa_c$ corresponds to the confinement phase. We also compute the variation of the critical $\kappa_c(T, \mu)$ when the temperature and chemical potential $T, \mu \ll \Lambda_{QCD}$ slightly vary. We also discuss the scaling $(x_i-x_j)^{-\gamma_{\rm det}}$ in the conformal phase.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0020">http://arxiv.org/abs/1308.0020</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-39339930723813833152013-08-04T00:03:00.009-07:002013-08-04T00:03:19.433-07:001308.0027 (Mohamed M. Anber)<h2 class="title"><a href="http://arxiv.org/abs/1308.0027">The abelian confinement mechanism revisited: new aspects of the<br /> Georgi-Glashow model</a> [<a href="http://arxiv.org/pdf/1308.0027">PDF</a>]</h2>Mohamed M. Anber<a name='more'></a><blockquote class="abstract">The confinement problem remains one of the most difficult problems in theoretical physics. An important step toward the solution of this problem is the Polyakov's work on abelian confinement. The Georgi-Glashow model is a natural testing ground for this mechanism which has been surprising us by its richness and wide applicability. In this work, we shed light on two new aspects of this model in 2+1 D. First, we develop a many-body description of the effective degrees of freedom. Namely, we consider a non-relativistic gas of W-bosons in the background of monopole-instanton plasma. Many-body treatment is a standard toolkit in condensed matter physics. However, we add a new twist by supplying the monopole-instantons as external background field. Using this construction, we calculate the exact form of the potential between two electric probes as a function of their separation. This potential is expressed in terms of the Meijer-G function which interpolates between logarithmic and linear behavior at small and large distances, respectively. Second, we develop a systematic approach to integrate out the effect of the W-bosons at finite temperature in the range 0<T<M_W, where M_W is the W-boson mass, starting from the full relativistic partition function of the Georgi-Glashow model. Using a heat kernel expansion that takes into account the non-trivial thermal holonomy, we show that the partition function describes a three-dimensional two-component Coulomb gas. We repeat our analysis using the many-body description which yields the same result and provides a check on our formalism. At temperatures close to the deconfinement temperature, the gas becomes essentially two-dimensional recovering the partition function of the dual sine-Gordon model that was considered in a previous work.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0027">http://arxiv.org/abs/1308.0027</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-75703052319830152682013-08-04T00:03:00.007-07:002013-08-04T00:03:18.724-07:001308.0127 (Aleksey Cherman et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0127">Resurgence in QFT: Unitons, Fractons and Renormalons in the Principal<br /> Chiral Model</a> [<a href="http://arxiv.org/pdf/1308.0127">PDF</a>]</h2>Aleksey Cherman, Daniele Dorigoni, Gerald V. Dunne, Mithat Unsal<a name='more'></a><blockquote class="abstract">We explain the physical role of non-perturbative saddle points of path integrals in theories without instantons, using the example of the asymptotically free two-dimensional principal chiral model (PCM). Standard topological arguments based on homotopy considerations suggest no role for non-perturbative saddles in such theories. However, resurgence theory, which unifies perturbative and non-perturbative physics, predicts the existence of several types of non-perturbative saddles associated with features of the large-order structure of perturbation theory. These points are illustrated in the PCM, where we find new non-perturbative `fracton' saddle point field configurations, and give a quantum interpretation of previously discovered `uniton' unstable classical solutions. The fractons lead to a semi-classical realization of IR renormalons in the circle-compactified theory, and yield the microscopic mechanism of the mass gap of the PCM.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0127">http://arxiv.org/abs/1308.0127</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-43886952308037016892013-08-04T00:03:00.005-07:002013-08-04T00:03:17.925-07:001308.0164 (Ralf-Arno Tripolt et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0164">The Effect of Fluctuations on the QCD Critical Point in a Finite Volume</a> [<a href="http://arxiv.org/pdf/1308.0164">PDF</a>]</h2>Ralf-Arno Tripolt, Jens Braun, Bertram Klein, Bernd-Jochen Schaefer<a name='more'></a><blockquote class="abstract">We investigate the effect of a finite volume on the critical behavior of the theory of the strong interaction (QCD) by means of a quark-meson model for two quark flavors. In particular, we analyze the effect of a finite volume on the location of the critical point in the phase diagram existing in our model. In our analysis, we take into account the effect of long-range fluctuations with the aid of renormalization group techniques. We find that these quantum and thermal fluctuations, absent in mean-field studies, play an import role for the dynamics in a finite volume. We show that the critical point is shifted towards smaller temperatures and larger values of the quark chemical potential if the volume size is decreased. This behavior persists for antiperiodic as well as periodic boundary conditions for the quark fields as used in many lattice QCD simulations.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0164">http://arxiv.org/abs/1308.0164</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-50284634838431535362013-08-04T00:03:00.003-07:002013-08-04T00:03:17.140-07:001308.0233 (Abhishek Mukherjee et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0233">Metropolis Monte Carlo on the Lefschetz thimble: application to a<br /> one-plaquette model</a> [<a href="http://arxiv.org/pdf/1308.0233">PDF</a>]</h2>Abhishek Mukherjee, Marco Cristoforetti, Luigi Scorzato<a name='more'></a><blockquote class="abstract">We propose a new algorithm based on the Metropolis sampling method to perform Monte Carlo integration for path integrals in the recently proposed formulation of quantum field theories on the Lefschetz thimble. The algorithm is based on a mapping between the curved manifold defined by the Lefschetz thimble of the full action and the flat manifold associated with the corresponding quadratic action. We discuss an explicit method to calculate the residual phase due to the curvature of the Lefschetz thimble. Finally, we apply this new algorithm to a simple one-plaquette model where our results are in perfect agreement with the analytic integration. We also show that for this system the residual phase does not represent a sign problem.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0233">http://arxiv.org/abs/1308.0233</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-59119297628173765402013-08-04T00:03:00.001-07:002013-08-04T00:03:16.182-07:001308.0302 (Claudio Bonati et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0302">The Maximal Abelian Gauge in SU(N) Gauge Theories and Thermal Monopoles<br /> for N = 3</a> [<a href="http://arxiv.org/pdf/1308.0302">PDF</a>]</h2>Claudio Bonati, Massimo D'Elia<a name='more'></a><blockquote class="abstract">We discuss and propose a proper extension of the Abelian projection based on the Maximal Abelian Gauge to SU(N) gauge theories. Based, on that, we investigate the properties of thermal Abelian monopoles in the deconfined phase of the SU(3) pure gauge theory. Such properties are very similar to those already found for SU(2), confirming the relevance of the magnetic component close to Tc and the possible condensation of thermal monopoles as the deconfinement temperature is crossed from above. Moreover, we study the correlation functions among monopoles related to different U(1) subgroups, which show interesting features and reveal the presence of non-trivial interactions.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0302">http://arxiv.org/abs/1308.0302</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-89290279732453880782013-07-31T00:18:00.009-07:002013-07-31T00:18:07.195-07:001307.7748 (Denes Sexty)<h2 class="title"><a href="http://arxiv.org/abs/1307.7748">Simulating full QCD at nonzero density using the complex Langevin<br /> equation</a> [<a href="http://arxiv.org/pdf/1307.7748">PDF</a>]</h2>Denes Sexty<a name='more'></a><blockquote class="abstract">The complex Langevin method is extended to full QCD at non-zero chemical potential. The use of gauge cooling stabilizes the simulations for smooth lattices. At large fermion mass the results are compared to HQCD limit, where the spatial hoppings are neglected, and good agreement is found. The method allows simulations also at high densities, all the way up to saturation.</blockquote>View original: <a href="http://arxiv.org/abs/1307.7748">http://arxiv.org/abs/1307.7748</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-25989045536935036972013-07-31T00:18:00.007-07:002013-07-31T00:18:04.155-07:001307.7923 (Ulf-G. Meißner)<h2 class="title"><a href="http://arxiv.org/abs/1307.7923">Nuclear lattice simulations: Status and perspectives</a> [<a href="http://arxiv.org/pdf/1307.7923">PDF</a>]</h2>Ulf-G. Meißner<a name='more'></a><blockquote class="abstract">I review the present status of nuclear lattice simulations. This talk is dedicated to the memory of Gerald E. Brown.</blockquote>View original: <a href="http://arxiv.org/abs/1307.7923">http://arxiv.org/abs/1307.7923</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-6238252211645098442013-07-31T00:18:00.005-07:002013-07-31T00:18:03.380-07:001307.7924 (Zong-Gang Mou et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.7924">Ensemble fermions for electroweak dynamics and the fermion preheating<br /> temperature</a> [<a href="http://arxiv.org/pdf/1307.7924">PDF</a>]</h2>Zong-Gang Mou, Paul M. Saffin, Anders Tranberg<a name='more'></a><blockquote class="abstract">We refine the implementation of ensemble fermions for the electroweak sector of the Standard Model, introduced previously. We consider the behavior of different observables as the size of the ensemble is increased and show that the dynamics converges for ensemble sizes small enough that simulations of the entire electroweak sector become numerically tractable. We apply the method to the computation of the effective preheating temperature during a fast electroweak transition, relevant for Cold Electroweak Baryogenesis. We find that this temperature is never below 20 GeV, and this in combination with the early results convincingly rules out Standard Model CP-violation as the origin of the baryon asymmetry of the Universe.</blockquote>View original: <a href="http://arxiv.org/abs/1307.7924">http://arxiv.org/abs/1307.7924</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-45130199316717379762013-07-31T00:18:00.003-07:002013-07-31T00:18:02.715-07:001307.8063 (Claudio Bonati et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.8063">The Magnetic Susceptibility of Strongly Interacting Matter across<br /> Deconfinement</a> [<a href="http://arxiv.org/pdf/1307.8063">PDF</a>]</h2>Claudio Bonati, Massimo D'Elia, Marco Mariti, Francesco Negro, Francesco Sanfilippo<a name='more'></a><blockquote class="abstract">We propose a method to determine the total magnetic susceptibility of strongly interacting matter by lattice QCD simulations, and present first numerical results for the theory with two light flavors, which suggest a very weak magnetic activity in the confined phase and the emergence of strong paramagnetism in the deconfined, Quark-Gluon Plasma phase.</blockquote>View original: <a href="http://arxiv.org/abs/1307.8063">http://arxiv.org/abs/1307.8063</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-73428135562530344932013-07-31T00:18:00.001-07:002013-07-31T00:18:01.801-07:001307.8098 (Sylvain Mogliacci et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.8098">Equation of State of hot and dense QCD: Resummed perturbation theory<br /> confronts lattice data</a> [<a href="http://arxiv.org/pdf/1307.8098">PDF</a>]</h2>Sylvain Mogliacci, Jens O. Andersen, Michael Strickland, Nan Su, Aleksi Vuorinen<a name='more'></a><blockquote class="abstract">We perform a detailed analysis of the predictions of resummed perturbation theory for the pressure and the second, fourth and sixth order diagonal quark number susceptibilities in a hot and dense quark-gluon plasma. First, we present a full one-loop calculation of the equation of state within hard-thermal-loop perturbation theory, and then perform a resummation of the existing four-loop weak coupling expression of the pressure, motivated by dimensional reduction. The convergence properties of the results are analyzed and their agreement with state-of-the-art lattice data discussed. Finally, we compare the full one-loop hard-thermal-loop results to previous ones that employ an expansion in the ratios of thermal masses and the temperature, concluding that the expansion converges reasonably fast.</blockquote>View original: <a href="http://arxiv.org/abs/1307.8098">http://arxiv.org/abs/1307.8098</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-40286090653569583132013-07-30T00:07:00.013-07:002013-07-30T00:07:12.891-07:001102.2264 (Bahman Dehnadi et al.)<h2 class="title"><a href="http://arxiv.org/abs/1102.2264">Charm Mass Determination from QCD Charmonium Sum Rules at Order<br /> alpha_s^3</a> [<a href="http://arxiv.org/pdf/1102.2264">PDF</a>]</h2>Bahman Dehnadi, Andre H. Hoang, Vicent Mateu, S. Mohammad Zebarjad<a name='more'></a><blockquote class="abstract">We determine the MS-bar charm quark mass from a charmonium QCD sum rules analysis. On the theoretical side we use input from perturbation theory at O(alpha_s^3). Improvements with respect to previous O(alpha_s^3) analyses include (1) an account of all available e+e- hadronic cross section data and (2) a thorough analysis of perturbative uncertainties. Using a data clustering method to combine hadronic cross section data sets from different measurements we demonstrate that using all available experimental data up to c.m. energies of 10.538 GeV allows for determinations of experimental moments and their correlations with small errors and that there is no need to rely on theoretical input above the charmonium resonances. We also show that good convergence properties of the perturbative series for the theoretical sum rule moments need to be considered with some care when extracting the charm mass and demonstrate how to set up a suitable set of scale variations to obtain a proper estimate of the perturbative uncertainty. As the final outcome of our analysis we obtain m_c(m_c) = 1.282 \pm 0.006_stat \pm 0.009_syst \pm 0.019)_pert \pm 0.010_alpha \pm 0.002_GG GeV. The perturbative error is an order of magnitude larger than the one obtained in previous O(alpha_s^3) sum rule analyses.</blockquote>View original: <a href="http://arxiv.org/abs/1102.2264">http://arxiv.org/abs/1102.2264</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-37920456570311047772013-07-30T00:07:00.011-07:002013-07-30T00:07:12.102-07:001307.7205 (Xiao-Yong Jin et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.7205">Finite size scaling study of $N_{\text{f}}=4$ finite density QCD on the<br /> lattice</a> [<a href="http://arxiv.org/pdf/1307.7205">PDF</a>]</h2>Xiao-Yong Jin, Yoshinobu Kuramashi, Yoshifumi Nakamura, Shinji Takeda, Akira Ukawa<a name='more'></a><blockquote class="abstract">We explore the phase space spanned by the temperature and the chemical potential for 4-flavor lattice QCD using the Wilson-clover quark action. In order to determine the order of the phase transition, we apply finite size scaling analyses to gluonic and quark observables including plaquette, Polyakov loop and quark number density, and examine their susceptibility, skewness, kurtosis and Challa-Landau-Binder cumulant. Simulations were carried out on lattices of a temporal size fixed at $N_{\text{t}}=4$ and spatial sizes chosen from $6^3$ up to $10^3$. Configurations were generated using the phase reweighting approach, while the value of the phase of the quark determinant were carefully monitored. The $\mu$-parameter reweighting technique is employed to precisely locate the point of the phase transition. Among various approximation schemes for calculating the ratio of quark determinants needed for $\mu$-reweighting, we found the Taylor expansion of the logarithm of the quark determinant to be the most reliable. Our finite-size analyses show that the transition is first order at $(\beta, \kappa, \mu/T)=(1.58, 0.1385, 0.584\pm 0.008)$ where $(m_\pi/m_\rho, T/m_\rho)=(0.822, 0.154)$. It weakens considerably at $(\beta, \kappa, \mu/T)=(1.60, 0.1371, 0.821\pm 0.008)$ where $(m_\pi/m_\rho, T/m_\rho)=(0.839, 0.150)$, and a crossover rather than a first order phase transition cannot be ruled out.</blockquote>View original: <a href="http://arxiv.org/abs/1307.7205">http://arxiv.org/abs/1307.7205</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-8819350775647718002013-07-30T00:07:00.009-07:002013-07-30T00:07:11.340-07:001307.7251 (Mario Kieburg et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.7251">Spectral Properties of the Wilson Dirac Operator and RMT</a> [<a href="http://arxiv.org/pdf/1307.7251">PDF</a>]</h2>Mario Kieburg, Jacobus J. M. Verbaarschot, Savvas Zafeiropoulos<a name='more'></a><blockquote class="abstract">Random Matrix Theory has been successfully applied to lattice Quantum Chromodynamics. In particular, a great deal of progress has been made on the understanding, numerically as well as analytically, of the spectral properties of the Wilson Dirac operator. In this paper, we study the infra-red spectrum of the Wilson Dirac operator via Random Matrix Theory including the three leading order $a^2$ correction terms that appear in the corresponding chiral Lagrangian. A derivation of the joint probability density of the eigenvalues is presented. This result is used to calculate the density of the complex eigenvalues, the density of the real eigenvalues and the distribution of the chiralities over the real eigenvalues. A detailed discussion of these quantities shows how each low energy constant affects the spectrum. Especially we consider the limit of small and large (which is almost the mean field limit) lattice spacing. Comparisons with Monte Carlo simulations of the Random Matrix Theory show a perfect agreement with the analytical predictions. Furthermore we present some quantities which can be easily used for comparison of lattice data and the analytical results.</blockquote>View original: <a href="http://arxiv.org/abs/1307.7251">http://arxiv.org/abs/1307.7251</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-46317979201458010592013-07-30T00:07:00.007-07:002013-07-30T00:07:10.060-07:001307.7480 (Juven Wang et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.7480">A Lattice Non-Perturbative Definition of 1+1D Anomaly-Free Chiral<br /> Fermions and Bosons</a> [<a href="http://arxiv.org/pdf/1307.7480">PDF</a>]</h2>Juven Wang, Xiao-Gang Wen<a name='more'></a><blockquote class="abstract">A non-perturbative definition of anomaly-free chiral fermions and bosons in 1+1D spacetime as finite quantum systems on 1D lattice is proposed. In particular, we show that the 3-5-4-0 chiral fermion theory, with two left-moving fermions of charge-3 and charge-4, and two right-moving fermions of charge-5 and charge-0 at low energy, can be put on a 1D spatial lattice without breaking the U(1) symmetry, if we include strong interactions between fermions. In general, we show that any 1+1D anomaly-free chiral matter theory (satisfying 't Hooft anomaly matching condition) can be defined as finite quantum systems on 1D lattice with on-site symmetry, if we include strong interactions between matter fields. Our approach provides another way, apart from Ginsparg-Wilson fermions approach, to avoid Nielsen-Ninomiya theorem's fermion-doubling challenge. As an additional remark, we prove the equivalence relation between 't Hooft anomaly matching condition and the boundary fully gapping rules.</blockquote>View original: <a href="http://arxiv.org/abs/1307.7480">http://arxiv.org/abs/1307.7480</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-10812141177172480002013-07-30T00:07:00.005-07:002013-07-30T00:07:06.599-07:001307.7497 (Stefano Capitani)<h2 class="title"><a href="http://arxiv.org/abs/1307.7497">Reducing the number of counterterms with new minimally doubled actions</a> [<a href="http://arxiv.org/pdf/1307.7497">PDF</a>]</h2>Stefano Capitani<a name='more'></a><blockquote class="abstract">We study a class of nearest-neighbor minimally doubled actions which depend on 2 continuous parameters. We calculate the contributions of the 3 possible counterterms in perturbation theory, and we find that for each counterterm there are curves in the parameter space on which its coefficient vanishes. One can thus construct renormalized actions that contain only 2 counterterms instead of the 3 of the standard Karsten-Wilczek or Borici-Creutz actions. Our investigations suggest the usefulness of analogous nonperturbative searches for values of the parameters for which the number of counterterms can be reduced. They can also be an inspiration to undertake a search for ultralocal minimally doubled actions with even better counterterm-reducing properties, including the optimal case in which all counterterms can be removed. Simulations of the latter actions will be much cheaper than the cases in which one needs to add counterterms to the bare actions, like the already conveniently inexpensive standard Karsten-Wilczek fermions. Finally, we also introduce minimally doubled fermions with next-to-nearest-neighbor interactions, which depend on 4 continuous parameters, as a further possibility in the search for renormalized actions with no counterterms.</blockquote>View original: <a href="http://arxiv.org/abs/1307.7497">http://arxiv.org/abs/1307.7497</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-72581923794351013832013-07-30T00:07:00.003-07:002013-07-30T00:07:05.253-07:001307.7523 (E. Megias et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.7523">Constituent Quarks and Gluons, Polyakov loop and the Hadron Resonance<br /> Gas Model</a> [<a href="http://arxiv.org/pdf/1307.7523">PDF</a>]</h2>E. Megias, E. Ruiz Arriola, L. L. Salcedo<a name='more'></a><blockquote class="abstract">Based on first principle QCD arguments, it has been argued in arXiv:1204.2424[hep-ph] that the vacuum expectation value of the Polyakov loop can be represented in the hadron resonance gas model. We study this within the Polyakov-constituent quark model by implementing the quantum and local nature of the Polyakov loop hep-ph/0412308, hep-ph/0607338. The existence of exotic states in the spectrum is discussed.</blockquote>View original: <a href="http://arxiv.org/abs/1307.7523">http://arxiv.org/abs/1307.7523</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-76295511995225855992013-07-30T00:07:00.001-07:002013-07-30T00:07:02.603-07:001307.7699 (Ali Davody)<h2 class="title"><a href="http://arxiv.org/abs/1307.7699">Bold Diagrammatic Monte Carlo Study of $φ^4$ Theory</a> [<a href="http://arxiv.org/pdf/1307.7699">PDF</a>]</h2>Ali Davody<a name='more'></a><blockquote class="abstract">By incorporating renormalization procedure into Bold Diagrammatic Monte Carlo (BDMC), we propose a method for studying quantum field theories in the strong coupling regime. BDMC essentially samples Feynman diagrams using local Metropolis-type updates and does not suffer from the sign problem. Applying the method to three dimensional $\phi^4$ theory, we analyze the strong coupling limit of the theory and confirm the existence of a nontrivial IR fixed point in agreement with prior studies. Interestingly, we find that working with bold correlation functions as building blocks of the Monte Carlo procedure, renders the scheme convergent and no further resummation method is needed.</blockquote>View original: <a href="http://arxiv.org/abs/1307.7699">http://arxiv.org/abs/1307.7699</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-42711559272145277802013-07-29T00:02:00.005-07:002013-07-29T00:02:04.994-07:001109.5109 (Mario Kieburg)<h2 class="title"><a href="http://arxiv.org/abs/1109.5109">Surprising Pfaffian factorizations in Random Matrix Theory with Dyson<br /> index $β=2$</a> [<a href="http://arxiv.org/pdf/1109.5109">PDF</a>]</h2>Mario Kieburg<a name='more'></a><blockquote class="abstract">In the past decades, determinants and Pfaffians were found for eigenvalue correlations of various random matrix ensembles. These structures simplify the average over a large number of ratios of characteristic polynomials to integrations over one and two characteristic polynomials only. Up to now it was thought that determinants occur for ensembles with Dyson index $\beta=2$ whereas Pfaffians only for ensembles with $\beta=1,4$. We derive a non-trivial Pfaffian determinant for $\beta=2$ random matrix ensembles which is similar to the one for $\beta=1,4$. Thus, it unveils a hidden universality of this structure. We also give a general relation between the orthogonal polynomials related to the determinantal structure and the skew-orthogonal polynomials corresponding to the Pfaffian. As a particular example we consider the chiral unitary ensembles in great detail.</blockquote>View original: <a href="http://arxiv.org/abs/1109.5109">http://arxiv.org/abs/1109.5109</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-37207852490646311982013-07-29T00:02:00.003-07:002013-07-29T00:02:03.909-07:001307.6997 (M. Hayakawa et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.6997">Running coupling constant and mass anomalous dimension of six-flavor<br /> SU(2) gauge theory</a> [<a href="http://arxiv.org/pdf/1307.6997">PDF</a>]</h2>M. Hayakawa, K. -I. Ishikawa, S. Takeda, N. Yamada<a name='more'></a><blockquote class="abstract">In the exploration of viable models of dynamical electroweak symmetry breaking, it is essential to locate the lower end of the conformal window and know the mass anomalous dimensions there for a variety of gauge theories. We calculate, with the Schr\"odinger functional scheme, the running coupling constant and the mass anomalous dimension of SU(2) gauge theory with six massless Dirac fermions in the fundamental representation. The calculations are performed on 6^4 to 24^4 lattices over a wide range of lattice bare coupling to take the continuum limit. The discretization errors for both quantities are removed perturbatively, and this removal turns out to increase a possible value of infrared fixed point and the mass anomalous dimension. We find that the running slows down and comes to a stop at 0.06 \lesssim 1/g^2 \lesssim 0.15 where the mass anomalous dimension is estimated to be 0.26 \lesssim \gamma^*_m \lesssim 0.74.</blockquote>View original: <a href="http://arxiv.org/abs/1307.6997">http://arxiv.org/abs/1307.6997</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-12342115948426591962013-07-29T00:02:00.001-07:002013-07-29T00:02:03.064-07:001307.7022 (M. Padmanath et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.7022">Spectroscopy of triply-charmed baryons from lattice QCD</a> [<a href="http://arxiv.org/pdf/1307.7022">PDF</a>]</h2>M. Padmanath, Robert G. Edwards, Nilmani Mathur, Michael Peardon<a name='more'></a><blockquote class="abstract">The spectrum of excitations of triply-charmed baryons is computed using lattice QCD including dynamical light quark fields. The spectrum obtained has baryonic states with well-defined total spin up to 7/2 and the low-lying states closely resemble the expectation from models with an SU(6)x O(3) symmetry. Energy splittings between extracted states, including those due to spin-orbit coupling in the heavy quark limit are computed and compared against data at other quark masses.</blockquote>View original: <a href="http://arxiv.org/abs/1307.7022">http://arxiv.org/abs/1307.7022</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-79365012356191404232013-07-26T00:48:00.009-07:002013-07-26T00:48:04.495-07:001307.6645 (Etsuko Itou)<h2 class="title"><a href="http://arxiv.org/abs/1307.6645">A novel scheme for the wave function renormalization of the composite<br /> operators</a> [<a href="http://arxiv.org/pdf/1307.6645">PDF</a>]</h2>Etsuko Itou<a name='more'></a><blockquote class="abstract">We propose a novel renormalization scheme for the hadronic operators. The renormalization factor of the operator in this scheme is normalized by the correlation function at tree level. If we focus on the pseudo scalar operator, then its renormalization factor is related to the mass renormalization factor of the fermion through the partially conserved axial-vector current (PCAC) relation. Using the renormalization factor for the pseudo scalar operator in our scheme, we obtain the mass anomalous dimension of the SU(3) gauge theory coupled to N_f=12 massless fundamental fermions, which has an infrared fixed point (IRFP). The mass anomalous dimension at the IRFP is estimated as gamma_m^*= 0.044_{-0.024}^{+0.025} (stat.)_{-0}^{+0.057} (syst.)_{-0.032}^{+0} (syst.).</blockquote>View original: <a href="http://arxiv.org/abs/1307.6645">http://arxiv.org/abs/1307.6645</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-7924348630364356733.post-88267459000295150852013-07-26T00:48:00.007-07:002013-07-26T00:48:03.846-07:001307.6647 (Martin Weigel et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.6647">Efficient simulation of the random-cluster model</a> [<a href="http://arxiv.org/pdf/1307.6647">PDF</a>]</h2>Martin Weigel, Eren Metin Elçi<a name='more'></a><blockquote class="abstract">The simulation of spin models close to critical points of continuous phase transitions is heavily impeded by the occurrence of critical slowing down. A number of cluster algorithms, usually based on the Fortuin-Kasteleyn representation of the Potts model, and suitable generalizations for continuous-spin models have been used to increase simulation efficiency. The first algorithm making use of this representation, suggested by Sweeny in 1983, has not found widespread adoption due to problems in its implementation. However, it has been recently shown that it is indeed more efficient in reducing critical slowing down than the more well-known algorithm due to Swendsen and Wang. Here, we present an efficient implementation of Sweeny's approach for the random-cluster model using recent algorithmic advances in dynamic connectivity algorithms.</blockquote>View original: <a href="http://arxiv.org/abs/1307.6647">http://arxiv.org/abs/1307.6647</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0