Yao-Yuan Mao, Ting-Wai Chiu
We derive the topological susceptibility to the one-loop order in the chiral effective theory of QCD, for an arbitrary number of flavors.
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We have computed the chiral susceptibility in quark-gluon plasma in presence of finite chemical potential and weak magnetic field within hard thermal loop approximation. First we construct the massive effective quark propagator in a thermomagnetic medium. Then we obtain completely analytic expression for the chiral susceptibility in weak magnetic field approximation. In the absence of magnetic field the thermal chiral susceptibility increases in presence of finite chemical potential. The effect of thermomagnetic correction is found to be very marginal as temperature is the dominant scale in we…
In the early days of QCD, the axial $U(1)$ anomaly was considered as a trigger for the breaking of the $SU(2)_L\times SU(2)_R$ symmetry through topological excitations of gluon fields. However, it has been a challenge for lattice QCD to quantify the effect. In this work, we simulate QCD at high temperatures with chiral fermions. The exact chiral symmetry enables us to separate the contribution from the axial $U(1)$ breaking from others among the susceptibilities in the scalar and pseudoscalar channels. Our result in two-flavor QCD indicates that the chiral susceptibility, which is conventional…
We calculate chiral susceptibilities in (2+1)-flavour QCD for different masses of the light quarks using the functional renormalisation group (fRG) approach to first-principles QCD. We follow the evolution of the chiral susceptibilities with decreasing masses as obtained from both the light-quark and the reduced quark condensate. The latter compares very well with recent results from the HotQCD collaboration for pion masses $m_π\gtrsim 100\,\text{MeV}$. For smaller pion masses, the fRG and lattice results are still consistent. In particular, the estimates for the chiral critical temperature ar…
The first two non-trivial moments of the distribution of the topological charge (or gluonic winding number), i.e., the topological susceptibility and the fourth cumulant, can be computed in lattice QCD simulations and exploited to constrain the pattern of chiral symmetry breaking. We compute these two topological observables at next-to-leading order in three-flavour Chiral Perturbation Theory, and we discuss the role played by the eta propagation in these expressions. For hierarchies of light-quark masses close to the physical situation, we show that the fourth cumulant has a much better sensi…
The chiral susceptibility is given by the scalar vacuum polarisation at zero total momentum. This follows directly from the expression for the vacuum quark condensate so long as a nonperturbative symmetry preserving truncation scheme is employed. For QCD in-vacuum the susceptibility can rigorously be defined via a Pauli-Villars regularisation procedure. Owing to the scalar Ward identity, irrespective of the form or Ansatz for the kernel of the gap equation, the consistent scalar vertex at zero total momentum can automatically be obtained and hence the consistent susceptibility. This enables ca…
In this work we compute the axion mass and, from this (exploiting a well-known relation), we also derive an expression for the QCD topological susceptibility in the finite-temperature case, both below and above the chiral phase transition at $T_c$, making use of a chiral effective Lagrangian model which includes the axion, the scalar and pseudoscalar mesons and implements the $U(1)$ axial anomaly of the fundamental theory. We also provide a numerical estimate of the topological susceptibility at $T=0$ (in the physical case of three light quark flavors) and discuss the question of the temperatu…
The SU(2) gauge theory with 8 fundamental fermions is studied using unimproved staggered regularization. A phase transition or a crossover at strong coupling, which can be a bulk transition. By using chiral random matrix model we analyze the chiral condensate of this system. We also report the chiral susceptibility and its volume dependence near the transition point.
We compute the magnetic susceptibility of the quark condensate and the polarization of quarks at zero temperature and in a uniform magnetic background. Our theoretical framework consists of two chiral models that allow to treat self-consistently the spontaneous breaking of chiral symmetry: the linear $σ-$model coupled to quarks, dubbed quark-meson model, and the Nambu-Jona-Lasinio model. We also perform analytic estimates of the same quantities within the renormalized quark-meson model, both in the regimes of weak and strong fields. Our numerical results are in agreement with the recent litera…
The topological susceptibility of the vacuum in quantum chromodynamics has been simulated numerically using the Asqtad improved staggered fermion formalism. At nonzero lattice spacing the residual fermion doublers (fermion ``tastes'') in the staggered fermion formalism give contributions to the susceptibility that deviate from conventional continuum chiral perturbation theory. In this brief report we estimate the taste-breaking artifact and compare it with results of recent simulations, finding that it accounts for roughly half of the scaling violation.
The chiral susceptibility, or the first derivative of the chiral condensate with respect to the quark mass, is often used as a probe for the QCD phase transition since the chiral condensate is an order parameter of $SU(2)_L \times SU(2)_R$ symmetry breaking. However, the chiral condensate also breaks the axial $U(1)$ symmetry, which is usually not paid attention to as it is already broken by anomaly and apparently gives little impact on the transition. We investigate the susceptibilities in the scalar and pseudoscalar channels in order to quantify how much the axial $U(1)$ breaking contributes…
Short-distance singularities in lattice correlators can modify their Symanzik expansion by leading to additional O($a$) lattice artifacts. At the example of the chiral condensate and the topological susceptibility, we show how to account for these lattice artifacts for Wilson twisted mass fermions and show that the property of automatic O($a$) improvement is preserved at maximal twist.
Chiral susceptibility and axial U(1) anomaly near the (pseudo-)critical temperature
利用精确手征对称Dirac算符，在理论上干净地分离两味格点QCD临界温度附近connected与disconnected chiral susceptibility中的纯axial U(1)破缺效应，并给出初步结果。
We investigate the QCD magnetic susceptibility chi_q for flavor SU(2) at finite temperature (T) beyond the chiral limit, using the liquid instanton model, defined in Euclidean space and modified by the T-dependent caloron solution. The background electromagnetic fields are induced to the QCD vacuum, employing the Schwinger method. We first compute the scalar (chiral) and tensor condensates as functions of T as well the current-quark mass m, signaling the correct universal chiral restoration patterns. It turns out that chi_q, given by the ratio of the two condensates, is a smoothly decreasing f…
In lattice QCD with Wilson-type quarks, the chiral symmetry is explicitly broken by the Wilson term on finite lattices. Though the symmetry is guaranteed to recover in the continuum limit, a series of non-trivial procedures are required to recover the correct renormalized theory in the continuum limit. Recently, a new use of the gradient flow technique was proposed, in which correctly renormalized quantities are evaluated in the vanishing flow-time limit. This enables us to directly study the chiral condensate and its susceptibility with Wilson-type quarks. Extending our previous study of the …
We study the 'spectral projector' method for the computation of the chiral condensate and the topological susceptibility, using $N_f=2+1+1$ dynamical flavors of maximally twisted mass Wilson fermions. In particular, we perform a study of the quark mass dependence of the chiral condensate $Σ$ and topological susceptibility $χ_{top}$ in the range $270 MeV < m_π < 500 MeV$ and compare our data with analytical predictions. In addition, we compute $χ_{top}$ in the quenched approximation where we match the lattice spacing to the $N_f=2+1+1$ dynamical simulations. Using the Kaon, $η$ and $η^{\prime}$…
We derive a novel model-independent result for the pion susceptibility in QCD via the isovector-pseudoscalar vacuum polarisation. In the neighbourhood of the chiral-limit, the pion susceptibility can be expressed as a sum of two independent terms. The first expresses the pion-pole contribution. The second is identical to the vacuum chiral susceptibility, which describes the response of QCD's ground-state to a fluctuation in the current-quark mass. In this result one finds a straightforward explanation of a mismatch between extant estimates of the pion susceptibility.
We compute the topological susceptibility $χ_t$ of 2+1-flavor lattice QCD with dynamical Möbius domain-wall fermions, whose residual mass is kept at 1 MeV or smaller. In our analysis, we focus on the fluctuation of the topological charge density in a "slab" sub-volume of the simulated lattice, as proposed by Bietenholz et al. The quark mass dependence of our results agrees well with the prediction of the chiral perturbation theory, from which the chiral condensate is extracted. Combining the results for the pion mass $M_π$ and decay constant $F_π$, we obtain $χ_t$ = 0.227(02)(11)$M_π^2 F_π^2$ …
We present results on QCD with four dynamical flavors in the temperature range $150$ MeV $\lesssim T \lesssim 500$ MeV. We have performed lattice simulations with Wilson fermions at maximal twist and measured Polyakov loop, chiral condensate and disconnected susceptibility, on lattices with spacings as fine as 0.065 fm. For most observables spacing effects are below statistical errors, which enables us to identify lattice results with continuum estimates. Our estimate of the pseudocritical temperature compares favorably with continuum results from staggered and domain wall fermions, confirming…
The chiral phase transition in the conventional random matrix model is the second order in the chiral limit, irrespective of the number of flavors N_f, because it lacks the U_A(1)-breaking determinant interaction term. Furthermore, it predicts an unphysical value of zero for the topological susceptibility at finite temperatures. We propose a new chiral random matrix model which resolves these difficulties by incorporating the determinant interaction term within the instanton gas picture. The model produces a second-order transition for N_f=2 and a first-order transition for N_f=3, and recovers…
We demonstrate that the QCD topological susceptibility nonperturbatively gets a significant contribution signaled by flavor-nonuniversal quark condensates at around the pseudo-critical temperature of the chiral crossover. It implies a remarkable flavor breaking in the axial anomaly as well as the QCD theta vacuum in high temperature QCD, which are almost flavor universal in the vacuum. A nontrivial flavor breaking is triggered by nonperturbative thermal loop corrections at around the chiral crossover, which is different from the trivial flavor violation just scaled by the quark mass ratio, obs…
We show that the nonlocal two-flavor Nambu--Jona-Lasinio model predicts the enhancement of both chiral and axial symmetry breaking as the chiral imbalance of hot QCD matter, regulated by a chiral chemical potential $μ_5$, increases. The two crossovers are reasonably close to each other in the range of $μ_5$ examined here and the pseudocritical temperatures rise with $μ_5$. The curvatures of the chiral and axial crossovers for the chiral quark chemical potential approximately coincide and give $κ_5 \simeq - 0.011$. We point out that the presence of $μ_5$ in thermodynamic equilibrium is inconsis…
We study the $U(1)_A$ anomaly in the high-temperature phase of $N_f=2+1$ lattice QCD with chiral fermions. Gauge ensembles are generated with Möbius domain-wall (MDW) fermions, and in the measurements the determinant is reweighted to that of overlap fermions. We report the results for the overlap Dirac spectrum, $U(1)_A$ susceptibility, and topological susceptibility at $T=204$ and $175$ MeV.
We determine the topological susceptibility $χ_t$ in two-flavor QCD using the lattice simulations at a fixed topological sector. The topological charge density is unambiguously defined on the lattice using the overlap-Dirac operator which possesses exact chiral symmetry. Simulations are performed on a $16^3 \times 32$ lattice at lattice spacing $\sim$ 0.12 fm at six sea quark masses $m_q$ ranging in $m_s/6$--$m_s$ with $m_s$ the physical strange quark mass. The $χ_t$ is extracted from the constant behavior of the time-correlation of flavor-singlet pseudo-scalar meson two-point function at larg…
We present a scheme for the analytic computation of renormalization functions on the lattice, using a symbolic manipulation computer language. Our first nontrivial application is a new three-loop result for the topological susceptibility.
We determine the topological susceptibility of the gauge configurations generated by lattice simulations using two flavors of optimal domain-wall fermion on the $ 16^3 \times 32 $ lattice with length 16 in the fifth dimension, at the lattice spacing $ a \simeq 0.1 $ fm. Using the adaptive thick-restart Lanczos algorithm, we project the low-lying eigenmodes of the overlap Dirac operator, and obtain the topological charge of each configuration, for eight ensembles with pion masses in the range $ 220-550 $ MeV. From the topological charge, we compute the topological susceptibility and the second …
The topological susceptibility is one of the few physical quantities that directly measure the properties of the QCD vacuum. Chiral perturbation theory predicts that in the small quark mass limit the topological susceptibility depends quadratically on the pion mass, approaching zero in the chiral limit. Lattice calculations have difficulty reproducing this behavior. In this paper we study the topological susceptibility on dynamical staggered fermion configurations. Our results indicate that the lattice spacing has to be small, around a~0.1fm for thin link staggered fermion actions to show the …
We calculate the quark number susceptibility in the deconfined phase of QCD using the hard thermal loop (HTL) approximation for the quark propagator. This improved perturbation theory takes into account important medium effects such as thermal quark masses and Landau damping in the quark-gluon plasma. We explicitly show that the Landau damping part in the quark propagator for spacelike quark momenta does not contribute to the quark number susceptibility due to the quark number conservation. We find that the quark number susceptibility only due to the collective quark modes deviates from that o…
We reanalyse the topological susceptibility assuming the possibility of a significant paramagnetic suppression of the three-flavour quark condensate and a correlated enhancement of vacuum fluctuations of $s\bar{s}$ pairs. Using the framework of resummed ChPT, we point out that simulations performed near the physical point, with a significant mass hierarchy between u,d and s dynamical quarks, are not able to disentangle the contributions from the quark condensate and sea $s\bar{s}$-pair fluctuations, and that simulations with three light quark masses of the same order are better suited for this…
This is the last in a series of papers on the topological susceptibility in the interacting instanton liquid model (IILM). We will derive improved finite temperature interactions to study the thermodynamic limit of grand canonical Monte Carlo simulations in the quenched and unquenched case with light, physical quark masses. In particular, we will be interested in chiral symmetry breaking. The paper culminates by giving, for the first time, a well-motivated temperature-dependent axion mass. Especially, this work finally provides a computation of the axion mass in the low temperature regime, $m^…
Topological Susceptibility and QCD Axion Mass: QED and NNLO corrections
通过QED和NNLO修正提高QCD拓扑易变性精度，从而提升QCD轴子质量的确定精度。
The divergences of the generating functional of quenched Chiral Perturbation theory (qCHPT) to one loop are computed in closed form. We show how the quenched chiral logarithms can be reabsorbed in the renormalization of the $B_0$ parameter of the leading order Lagrangian. Finally, we do the chiral power counting for the quenched case and show that also finite loop corrections may diverge in the chiral limit.
We consider chiral loop corrections to the effective couplings which describe the strong interactions of two heavy mesons of even or odd parities and a light pseudoscalar meson, within a framework which combines heavy quark effective theory and chiral perturbation theory. The strong couplings are extracted from the experimental results for the decay widths, after including chiral corrections. We find that the introduction of positive parity heavy meson fields into the framework gives relevant contributions to the chiral loop corrections of the effective couplings. The counterterms' contributio…
Polyakov Loop Susceptibility and Correlators in the Chiral Limit
本文在 $N_f=2+1$ HISQ 模型中研究轻夸克质量趋近手征极限时 Polyakov loop 的磁化率、拐点及关联行为，初步结果表明其对手征相变不敏感且对轻夸克质量依赖性极小。
QCD thermodynamics with dynamical chiral fermions
本研究采用含overlap费米子的格点模拟研究热QCD性质，测定拓扑磁化率并对各拓扑扇区手征可观测量求和，验证手征磁化率体积依赖与相变交叉特性相符，还分析了overlap Dirac算符能谱的体积、温度依赖，结果基于$N_t=8$的时间格点设置。
As a test of the chiral properties of the improved Asqtad (staggered fermion) action, we have been measuring the topological susceptibility as a function of quark masses for 2 + 1 dynamical flavors. We report preliminary results, which show reasonable agreement with leading order chiral perturbation theory for lattice spacing less than 0.1 fm. The total topological charge, however, shows strong persistence over Monte Carlo time.
We calculate the divergences of the generating functional of quenched Chiral Perturbation Theory at one loop, and renormalize the theory by an appropriate definition of the counterterms. We show that the quenched chiral logarithms can be reabsorbed in the renormalization of the B_0 parameter which, at lowest order, is proportional to the vacuum expectation value of the scalar quark density. Finally, we calculate several quantities at one loop to analyze the modifications induced by quenching in the finite part of the one-loop corrections. We point out that some of the finite loop corrections m…
We report preliminary results on the chiral and deconfinement aspects of the QCD transition at finite temperature using the Highly Improved Staggered Quark (HISQ) action on lattices with temporal extent of N_τ=6 and 8. The chiral aspects of the transition are studied in terms of quark condensates and the disconnected chiral susceptibility. We study the deconfinement transition in terms of the strange quark number susceptibility and the renormalized Polyakov loop. We made continuum estimates for some quantities and find reasonably good agreement between our results and the recent continuum extr…
We investigate the QCD topological susceptibility $χ_t$ by using the nonlocal chiral quark model (NL$χ$QM). This model is based on the liquid instanton QCD-vacuum configuration in which $\mathrm{SU}(3)$ flavor symmetry is explicitly broken by the current quark mass $(m_{u,d},m_s)\approx(5,135)$ MeV. To compute $χ_t$, the local topological charge density operator $Q_t(x)$ is derived from the effective partition function of NL$χ$QM. We take into account the contributions from the leading-order (LO) ones $\sim\mathcal{O}(N_c)$ in the $1/N_c$ expansion. We also verify that the analytical expressio…
We calculate the finite volume corrections to meson masses and decay constants in two and three flavour Chiral Perturbation Theory to two-loop order. The analytical results are compared with the existing result for the pion mass in two-flavour ChPT and the partial results for the other quantities. We present numerical results for all quantities.
In this paper we present chiral extrapolation formulas for the generalized form factors connected to the first moments of chiral-even generalized parton distributions. For the description of QCD at low energies we employ the framework of two-flavor covariant baryon chiral perturbation theory at full one-loop accuracy. Our results are well suited for the extrapolation of lattice QCD data to physical quark masses.
We study the region of the QCD phase transition using 2+1 flavors of domain wall fermions (DWF) and a $16^3 \times 8$ lattice volume with a fifth dimension of $L_s = 32$. The disconnected light quark chiral susceptibility, quark number susceptibility and the Polyakov loop suggest a chiral and deconfining crossover transition lying between 155 and 185 MeV for our choice of quark mass and lattice spacing. In this region the lattice scale deduced from the Sommer parameter $r_0$ is $a^{-1} \approx 1.3$ GeV, the pion mass is $\approx 300$ MeV and the kaon mass is approximately physical. The peak in…
Chiral perturbation theory predicts that in quantum chromodymamics light dynamical quarks suppress the topological (instanton) susceptibility. We investigate this suppression through direct numerical simulation using the Asqtad improved lattice fermion action. This action holds promise for carrying out nonperturbative simulations over a range of quark masses for which chiral perturbation theory is expected to converge. To test the effectiveness of the action in capturing instanton physics, we measure the topological susceptibility as a function of quark masses with 2+1 dynamical flavors. Our r…
Topological susceptibility and QCD phase transition with 2+1 flavor Möbius domain wall fermion at finite temperature
研究有限温度下2+1味莫比乌斯域墙费米子的拓扑易变性与QCD相变，计算楚塞尔凝聚和断开易变性，探讨不同温度下的结果。
Using a reweighting technique combined with a low-mode truncation of the fermionic determinant, we estimate the quark-mass dependence of the QCD topological susceptibility with overlap fermions. In contrast to previous lattice simulations which all used non-chiral fermions, our results appear to be consistent with the simple continuum model of Dürr. This indicates that at current lattice spacings the use of the index theorem might not be justified and the fermionic definition of the charge might be needed.
We compute the topological susceptibility $χ_t$ of lattice QCD with $2+1$ dynamical quark flavors described by the Möbius domain wall fermion. Violation of chiral symmetry as measured by the residual mass is kept at $\sim$1 MeV or smaller. We measure the fluctuation of the topological charge density in a `slab' sub-volume of the simulated lattice using the method proposed by Bietenholz {\it et al.} The quark mass dependence of $χ_t$ is consistent with the prediction of chiral perturbation theory, from which the chiral condensate is extracted as $Σ^{\overline{\rm MS}} (\mbox{2GeV}) = [274(13)(2…
There are currently two singularity-free universal expressions for the topological susceptibility in QCD, one based on the Yang-Mills gradient flow and the other on density-chain correlation functions. While the latter link the susceptibility to the anomalous chiral Ward identities, the gradient flow permits the emergence of the topological sectors in lattice QCD to be understood. Here the two expressions are shown to coincide in the continuum theory, for any number of quark flavours in the range where the theory is asymptotically free.
We examine quenched chiral logarithms in lattice QCD with overlap Dirac quarks. From our data of m_pi^2, we determine the coefficient of quenched chiral logarithm delta = 0.203(14), 0.176(17), 0.193(17) and 0.200(13) for lattices of sizes 8^3 times 24, 10^3 times 24, 12^3 times 24 and 16^3 times 32 respectively. Also, for the first three lattice sizes, we measure the index susceptibility of the overlap Dirac operator, and use the exact relation between the index susceptibility and the eta' mass in quenched chiral perturbation theory to obtain an independent determination of delta = 0.198(27), …
In this paper we study the properties of QCD at nonzero chiral density $ρ_5$, which is introduced through chiral chemical potential $μ_5$. The study is performed within lattice simulation of QCD with dynamical rooted staggered fermions. We first check that $ρ_5$ is generated at nonzero $μ_5$ and in the chiral limit observe $ρ_5 \sim Λ_{QCD}^2 μ_5$. We also test the possible connection between confinement and topological fluctuations. To this end, we measured the topological susceptibility $χ_{\mbox{\footnotesize top}}$ and string tension $σ$ for various values of $μ_5$. We observed that both s…
Chiral and $U(1)_A$ symmetries in background magnetic fields from lattice QCD
该研究利用晶格量子色动力学，在背景磁场中研究量子色动力学的手征和单重态U(1)_A对称性，确定相关磁化率差，通过数值计算得出在特定系综上的结果，首次对背景磁场中手征和单重态U(1)_A伙伴磁化率分裂进行晶格量子色动力学研究。
We compute the topological charge and its susceptibility in finite temperature (2+1)-flavor QCD on the lattice applying a gradient flow method. With the Iwasaki gauge action and nonperturbatively $O(a)$-improved Wilson quarks, we perform simulations on a fine lattice with~$a\simeq0.07\,\mathrm{fm}$ at a heavy $u$, $d$ quark mass with $m_π/m_ρ\simeq0.63$ but approximately physical $s$ quark mass with $m_{η_{ss}}/m_ϕ\simeq0.74$. In a temperature range from~$T\simeq174\,\mathrm{MeV}$ ($N_t=16$) to $697\,\mathrm{MeV}$ ($N_t=4$), we study two topics on the topological susceptibility. One is a compa…
The chiral magnetization properties of cold and hot vacua are studied using quenched simulations in lattice Yang-Mills theory. In weak external magnetic fields the magnetization is proportional to the first power of the magnetic field. We evaluate numerically the coefficient of the proportionality (the chiral susceptibility) using near-zero eigenmodes of overlap fermions. We found that the product of the chiral susceptibility and the chiral condensate equals to 46(3) MeV. This value is very close to the phenomenological value of 50 MeV. In strong fields the magnetization is a nonlinear functio…
We address a long standing problem regarding topology in lattice simulations of QCD with unimproved Wilson fermions. Earlier attempt with unimproved Wilson fermions at β=5.6 to verify the suppression of topological susceptibility with decreasing quark mass (m_q) was unable to unambiguously confirm the suppression. We carry out systematic calculations for two degenerate flavours at two different lattice spacings (β= 5.6 and 5.8). The effects of quark mass, lattice volume and the lattice spacing on the spanning of different topological sectors are presented. We unambiguously demonstrate the supp…
We study the topological susceptibility, chi, in QCD with two quark flavours using lattice field configurations that have been produced with an O(a)-improved clover quark action. We find clear evidence for the expected suppression at small quark mass, m_q, and examine the variation of $χ$ with this mass and the lattice spacing, a. A joint continuum and chiral extrapolation yields good agreement with theoretical expectations as (a, m_q) -> 0. A moderate increase in autocorrelation is observed on the more chiral ensembles, but within large statistical errors. Finite volume effects are negligible…
We present results of our computation of the topological susceptibility with $N_f=2$ and $N_f=2+1+1$ flavours of maximally twisted mass fermions, using the method of spectral projectors. We perform a detailed study of the quark mass dependence and discretization effects. We make an attempt to confront our data with chiral perturbation theory and extract the chiral condensate from the quark mass dependence of the topological susceptibility. We compare the value with the results of our direct computation from the slope of the mode number. We emphasize the role of autocorrelations and the necessi…
We study the spatial inhomogeneity of the Polyakov loop induced by inhomogeneous chiral condensates. We formulate an effective model of gluons on the background fields of chiral condensates, and perform its lattice simulation. On the background of inhomogeneous chiral condensates, the Polyakov loop exhibits an in-phase spatial oscillation with the chiral condensates. We also analyze the heavy quark potential and show that the inhomogeneous Polyakov loop indicates the inhomogeneous confinement of heavy quarks.
In preparation of lattice studies of the two-color QCD phase diagram we study chiral restoration and deconfinement at finite temperature with two flavors of staggered quarks using an RHMC algorithm on GPUs. We first study unquenching effects in local Polyakov loop distributions, and the Polyakov loop potential obtained via Legendre transformation, in a fixed-scale approach for heavier quarks. We also present the chiral condensate and the corresponding susceptibility over the lattice coupling across the chiral transition for lighter quarks. Using Ferrenberg-Swendsen reweighting we extract the m…
We reexamine the estimate of the neutron Electric Dipole Moment (NEDM) from chiral and QCD spectral sum rules (QSSR) approaches. In the former, we evaluate the pion mass corrections which are about 5% of the leading Log. results. However, the chiral estimate can be affected by the unknown value of the renormalizaton scale nu. For QSSR, we analyze the effect of the nucleon interpolating currents on the existing predictions. We conclude that previous QSSR results are not obtained within the optimal choice of these operators, which lead to an overestimate of these results by about a factor 4. The…
We present a study of the topological susceptibility $χ$ on the lattice for full QCD with 2 and 4 flavours of staggered fermions at zero and finite temperature T. We find that $χ$ presents a sharp drop across the deconfinement transition. We also study the dependence of $χ$ on the quark mass at T=0: we have no conclusive evidence for the expected chiral behaviour.
Considering the strong field approximation we compute the hard thermal loop pressure at finite temperature and chemical potential of hot and dense deconfined QCD matter in lowest Landau level in one-loop order. We consider the anisotropic pressure in the presence of the strong magnetic field i.e., longitudinal and transverse pressure along parallel and perpendicular to the magnetic field direction. As a first effort, we compute and discuss the anisotropic quark number susceptibility of deconfined QCD matter in lowest Landau level. The longitudinal quark number susceptibility is found to increa…
We compare lattice QCD determinations of topological susceptibility using a gluonic definition from the gradient flow and a fermionic definition from the spectral projector method. We use ensembles with dynamical light, strange and charm flavors of maximally twisted mass fermions. For both definitions of the susceptibility we employ ensembles at three values of the lattice spacing and several quark masses at each spacing. The data are fitted to chiral perturbation theory predictions with a discretization term to determine the continuum chiral condensate in the massless limit and estimate the o…
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