arXiv subjects

Mushtaq Loan

Publications and source records attributed to Mushtaq Loan.

At least 19 recordsLinked to original sources

arXiv2026

One-Loop Renormalization of the Improved Energy-Momentum Tensor in Lattice QCD

We present the one-loop renormalization of the improved gluonic energy-momentum tensor (EMT) by employing a three-loop-improved clover discretization of the field-strength tensor in pure SU(3) lattice gauge theory. The renormalization factor is extracted by matching the amputated two-gluon matrix element of the lattice energy-momentum tensor to the continuum MSbar scheme. The one-loop contribution is separated into sail, operator-tadpole, and external-leg corrections, each expressed in terms of a minimal set of scalar Brillouin-zone integrals to obtain the explicit expression for the finite lattice coefficient B_lat(u_0) and the multiplicative renormalization factor Z_T(u_0) associated with the traceless spin-2 component of the energy-momentum tensor. A key result, obtained in this framework, is the clear distinction between two sectors: the spin-2 sector, governed by Z_T, and the scalar trace sector, which encompasses the Yang-Mills trace anomaly. The trace is determined by the scalar operator F_{ρσ}F_{ρσ} and the Yang-Mills beta function, rather than by the spin-2 renormalization factor. The renormalized EMT modifies the normalization and short-distance behaviour of energy-density correlators through both traceless and scalar-channel contributions. Comparison with existing lattice thermodynamic data demonstrates that the improved operator accurately reproduces the expected temperature dependence of the trace anomaly and offers a systematically improvable framework for investigating the equation of state, gluon condensate, and transport coefficients in lattice QCD.

hep-lat↗

arXiv2023

Entropy Density and Speed of Sound from Improved Energy-Momentum Tensor in Lattice QCD

We present a lattice calculation of the entropy density $s/T^{3}$ and speed of sound $c_{s}^{2}$ of gluedynamics near the critical temperature, $T_{c}$, in the deconfined phase. By exploring the temperature dependence of entropy density in this region, we aim to analyse the significant discrepancies between the previous computations. The calculation of entropy density is carried out by numerical simulations of $O(a^{4})$ mean-field improved energy-momentum tensor (EMT) of SU(3) gauge theory on the lattice. We expand on reaching $O(a^{4})$ improvement using tadpole-improved Symanzik action. The entropy density is calculated directly from the expectation value of the space-time component of the improved EMT in the presence of shifted boundary conditions at several lattice spacings ($a \approx 0.043 - 0.012$ fm). The absence of ultraviolet divergences and the minimal finite-size effects allow for the precision determination of the entropy density and its extrapolation to the continuum limit. As expected, the resulting entropy density displays the expected behaviour of rapid increase near the critical temperature in the deconfined phase followed by a slow increase in $2T_{c}\leq T\leq 3T_{c}$ region, suggesting a logarithmic dependence on the temperature. A quantitative comparison of $s/T^{3}$ shows good agreement with Pade approximation and lattice results of previous high-precision data obtained using the gradient flow method. We observe that at temperatures of about $3T_{c}$, deviations of entropy density from the Stefan-Boltzmann value for a free theory are about 10$\%$. It is shown that the speed of sound in SU(3) gluedynamics is found to be $c_{s}^{2}\leq 0.333$ in the temperature region $1.06T_{c}\leq T\leq 3.05T_{c}$ explored in this study. The results are found to agree with the corresponding analytic and numerical estimates.

hep-lat↗

arXiv2011

Search for H dibaryon on the lattice

We investigate the H-dibaryon, an $I(J^{P})=0(0^{+})$ with $s=-2$, in the chiral and continuum regimes on anisotropic lattices in quenched QCD. Simulations are performed on very coarse lattices with refined techniques to obtain results with high accuracy over a spatial lattice spacing in the range of $a_{s} \sim 0.19 - 0.41$ fm. We present results for the energy difference between the ground state energy of the hexa-quark stranglet and the free two-baryon state from our ensembles. A negative binding energy observed in the chirally extrapolated results leads to the conclusion that the measured hexa-quark state is bound. This is further confirmed by the attractive interaction in the continuum limit with the observed H-dibaryon bound by $\sim 47$ MeV.

hep-lat↗

arXiv2010

Foot Bone in Vivo: Its Center of Mass and Centroid of Shape

This paper studies foot bone geometrical shape and its mass distribution and establishes an assessment method of bone strength. Using spiral CT scanning, with an accuracy of sub-millimeter, we analyze the data of 384 pieces of foot bones in vivo and investigate the relationship between the bone's external shape and internal structure. This analysis is explored on the bases of the bone's center of mass and its centroid of shape. We observe the phenomenon of superposition of center of mass and centroid of shape fairly precisely, indicating a possible appearance of biomechanical organism. We investigate two aspects of the geometrical shape, (i) distance between compact bone's centroid of shape and that of the bone and (ii) the mean radius of the same density bone issue relative to the bone's centroid of shape. These quantities are used to interpret the influence of different physical exercises imposed on bone strength, thereby contributing to an alternate assessment technique to bone strength.

physics.bio-ph↗

arXiv2010

Dynamic Principles of Center of Mass in Human Walking

We present results of an analytic and numerical calculation that studies the relationship between the time of initial foot contact and the ground reaction force of human gait and explores the dynamic principle of center of mass. Assuming the ground reaction force of both feet to be the same in the same phase of a stride cycle, we establish the relationships between the time of initial foot contact and the ground reaction force, acceleration, velocity, displacement and average kinetic energy of center of mass. We employ the dispersion to analyze the effect of the time of the initial foot contact that imposes upon these physical quantities. Our study reveals that when the time of one foot's initial contact falls right in the middle of the other foot's stride cycle, these physical quantities reach extrema. An action function has been identified as the dispersion of the physical quantities and optimized analysis used to prove the least-action principle in gait. In addition to being very significant to the research domains such as clinical diagnosis, biped robot's gait control, the exploration of this principle can simplify our understanding of the basic properties of gait.

physics.bio-ph↗

arXiv2009

Distribution Principle of Bone Tissue

Using the analytic and experimental techniques we present an exploratory study of the mass distribution features of the high coincidence of centre of mass of heterogeneous bone tissue in vivo and its centroid of geometry position. A geometric concept of the average distribution radius of bone issue is proposed and functional relation of this geometric distribution feature between the partition density and its relative tissue average distribution radius is observed. Based upon the mass distribution feature, our results suggest a relative distance assessment index between the center of mass of cortical bone and the bone center of mass and establish a bone strength equation. Analysing the data of human foot in vivo, we notice that the mass and geometric distribution laws have expanded the connotation of Wolff's law, which implies a leap towards the quantitative description of bone strength. We finally conclude that this will not only make a positive contribution to help assess osteoporosis, but will also provide guidance to exercise prescription to the osteoporosis patients.

physics.bio-ph↗

arXiv2009

f(2010) in Lattice QCD

We present a search for the possible $I(J^{P})=0(2^{+})$ tetraquark state with $ss{\bar s}{\bar s}$ quark content in quenched improved anisotropic lattice QCD. Using various local and non-local interpolating fields we determine the energies of ground-state and second ground state using variational method. The state is found to be consistent with two-particle scattering state, which is checked to exhibit the expected volume dependence of the spectral weights. In the physical limit, we obtain for the ground state, a mass of $2123(33)(58)$ MeV which is higher than the mass of experimentally observed $f(2010)$. The lattice resonance signal obtained in the physical region does not support a localized $J^{P} =2^{+}$ tetraquark state in the pion mass region of $300 - 800$ MeV. We conclude that the $4q$ system in question appears as a two-particle scattering state in the quark mass region explored here.

hep-lat↗

arXiv2009

Least Action Principle in Gait

We apply the laws of human gait vertical ground reaction force and discover the existence of the phenomenon of least action principle in gait. Using a capacitive mat transducer system, we obtain the variations of human gait vertical ground reaction force and establish a structure equation for the resultant of such a force. Defining the deviation of vertical force as an action function, we observe from our gait optimization analysis the least action principle at half of the stride time. We develop an evaluation index of mechanical energy consumption based upon the least action principle in gait. We conclude that these observations can be employed to enhance the accountability of gait evaluation.

physics.bio-ph↗

arXiv2008

Critical Behavior of Ferromagnetic Ising Model on Triangular Lattice

We apply a new updating algorithm scheme to investigate the critical behavior of the two-dimensional ferromagnetic Ising model on a triangular lattice with nearest neighbour interactions. The transition is examined by generating accurate data for large lattices with $L=8,10,12,15,20,25,30,40,50$. The spin updating algorithm we employ has the advantages of both metropolis and single-update methods. Our study indicates that the transition to be continuous at $T_c=3.6403(2)$. A convincing finite-size scaling analysis of the model yield $ν=0.9995(21)$, $β/ν=0.12400(18)$, $γ/ν=1.75223(22)$, $γ'/ν=1.7555(22)$, $α/ν=0.00077(420)$ (scaling) and $α/ν=0.0010(42)$(hyperscaling) respectively. Estimates of present scheme yield accurate estimates for all critical exponents than those obtained with Monte Carlo methods and show an excellent agreement with their well-established predicted values.

cond-mat.stat-mech↗

arXiv2008

Study of Possible Proton-Antiproton Hexaquark State in Lattice QCD

We have used standard techniques of lattice quantum chromodynamics to look for evidence of the spin-zero six quark flavour singlet state ($J^{PC}=0^{-+}$) observed by BES Collaboration, and to determine the splitting between the mass of the possible proton-antiproton and the mass of two protons, its threshold. Using the various interpolating fields we find indications that for sufficiently light quarks proton-antiproton is slightly above the $2m_{p}$ threshold. The lattice resonance signal of binding observed near the physical and continuum regimes do not support the existence of proton-antiproton state as a spin-zero hexaquark state.

hep-lat↗

arXiv2008

Lowest-lying Tetra-Quark Hadrons in Anisotropic Lattice QCD

We present a detailed study of lowest-lying $q^{2}\bar{q}^{2}$ hadrons in quenched improved anisotropic lattice QCD. Using the $ππ$ and diquark-antidiquark local and smeared operators, we attempt to isolate the signal for $I(J^{P})=0(0^{+}), 2(0^{+})$ and $1(1^{+})$ states in two flavour QCD. In the chiral limit of light-quark mass region, the lowest scalar $4q$ state is found to have a mass, $m^{I=0}_{4q}=927(12)$ MeV, which is slightly lower than the experimentally observed $f_{0}(980)$. The results from our variational analysis do not indicate a signature of a tetraquark resonance in I=1 and I=2 channels. After the chiral extrapolation the lowest $1(1^{+})$ state is found to have a mass, $m^{I=1}_{4q}=1358(28)$ MeV. We analysed the static $4q$ potential extracted form a tetraquark Wilson loop and illustrated the behaviour of the $4q$ state as a bound state, unbinding at some critical diquark separation. From our analysis we conclude that scalar $4q$ system appears as a two-pion scattering state and that there is no spatially-localised $4q$ state in the light-quark mass region.

hep-lat↗

arXiv2008

H-Dibaryon from Lattice QCD with Improved Anisotropic Actions

The six quark state(uuddss) called H dibaryon($J^P=0^+$,$S=-2$) has been calculated to study its existence and stability. The simulations are performed in quenched QCD on $8^3 \times 24$ and $16^3 \times 48$ anisotropic lattices with Symanzik improved gauge action and Clover fermion action. The gauge coupling is $β=2.0$ and aspect ratio $ξ=a_s/a_t=3.0$. Preliminary results indicate that mass of H dibaryon is 2134(100)Mev on $8^3 \times 24$ lattice and 2167(59)Mev on $16^3 \times 48$ respectively. It seems that the radius of H dibaryon is very large and the finite size effect is very obvious.

hep-lat↗

arXiv2008

Revisiting glueball wave functions at zero and finite temperature

We study the sizes and thermal properties of glueballs in a three dimensional compact Abelian gauge model on improved lattice. We predict the radii of $\sim 0.60$ and $\sim 1.12$ in the units of string tension, or $\sim 0.28$ and $\sim 0.52$ fm, for the scalar and tensor glueballs, respectively. We perform a well controlled extrapolation of the radii to the continuum limit and observe that our results agree with the predicted values. Using Monte Carlo simulations, we extract the pole-mass of the lowest scalar and tensor glueballs from the temporal correlators at finite temperature. We see a clear evidence of the deconfined phase, and the transition appears to be similar to that of the two-dimensional XY model as expected from universality arguments. Our results show no significant changes in the glueball wave functions and masses in the deconfined phase.

hep-lat↗

arXiv2006

Glueball Wave Functions in U(1) Lattice Gauge Theory

Standard Monte Carlo simulations have been performed for 3-dimensional U(1) lattice gauge model on improved lattices to measure the wavefunction and size of the scalar and the tensor glueballs. Our results show the radii of ~ 0.60 and ~ 1.12 in the units of string tension, or ~0.28 and ~0.52 fm, for the scalar and tensor glueballs, respectively. At finite temperature we see clear evidence of the deconfined phase, and the transition appears to be similar to that of the two-dimensional XY model as expected from universality arguments. Preliminary results show no significant changes in the glueball wave functions and the masses in the deconfined phase.

hep-lat↗

arXiv2006

Sizes of Lightest Glueballs in SU(3) Lattice Gauge Theory

Standard Monte Carlo simulations have been performed on improved lattices to measure the wave functions and sizes of the scalar and tensor glueballs at four lattice spacings in the range $a= 0.05 - 0.145$ fm. Systematic errors from discretization and finite volume are studied. Our results in the continuum limit show that the size of the tensor state is approximately two times as large as that of the scalar glueball.

hep-lat↗

arXiv2005

Monte Carlo study of glueball masses in the Hamiltonian limit of SU(3) lattice gauge theory

Using Standard Euclidean Monte Carlo techniques, we discuss in detail the extraction of the glueball masses of 4-dimensional SU(3) lattice gauge theory in the Hamiltonian limit, where the temporal lattice spacing is zero. By taking into account the renormalization of both the anisotropy and the Euclidean coupling, we calculate the string tension and masses of the scalar, axial vector and tensor states using standard Wilson action on increasingly anisotropic lattices, and make an extrapolation to the Hamiltonian limit. The results are compared with estimates from various other Hamiltonian and Euclidean studies. We find that more accurate determination of the glueball masses and the mass ratios has been achieved and the results are a significant improvement upon previous Hamiltonian estimates. The continuum predictions are then found by extrapolation of results obtained from smallest values of spatial lattice spacing. For the lightest scalar, tensor and axial vector states we obtain masses of $m_{0^{++}}=1654 \pm 83$ MeV, $m_{2^{++}}=2272\pm 115$ MeV and $m_{1^{+-}}=2940\pm 165$ MeV, respectively. These are consistent with the estimates obtained in the previous studies in the Euclidean limit. The consistency is a clear evidence of universality between Euclidean and Hamiltonian formulations. From the accuracy of our estimates, we conclude that the standard Euclidean Monte Carlo method is a reliable technique for obtaining results in the Hamiltonian version of the theory, just as in Euclidean case.

hep-lat↗

arXiv2004

Hamiltonian Study of Improved $U(1$ Lattice Gauge Theory in Three Dimensions

A comprehensive analysis of the Symanzik improved anisotropic three-dimensional U(1) lattice gauge theory in the Hamiltonian limit is made. Monte Carlo techniques are used to obtain numerical results for the static potential, ratio of the renormalized and bare anisotropies, the string tension, lowest glueball masses and the mass ratio. Evidence that rotational symmetry is established more accurately for the Symanzik improved anisotropic action is presented. The discretization errors in the static potential and the renormalization of the bare anisotropy are found to be only a few percent compared to errors of about 20-25% for the unimproved gauge action. Evidence of scaling in the string tension, antisymmetric mass gap and the mass ratio is observed in the weak coupling region and the behaviour is tested against analytic and numerical results obtained in various other Hamiltonian studies of the theory. We find that more accurate determination of the scaling coefficients of the string tension and the antisymmetric mass gap has been achieved, and the agreement with various other Hamiltonian studies of the theory is excellent. The improved action is found to give faster convergence to the continuum limit. Very clear evidence is obtained that in the continuum limit the glueball ratio $M_{S}/M_{A}$ approaches exactly 2, as expected in a theory of free, massive bosons.

hep-lat↗

arXiv2003

Renormalization of Anisotropy and Glueball Masses on Tadpole Improved Lattice Gauge Action

The Numerical calculations for tadpole-improved U(1) lattice gauge theory in three-dimensions on anisotropic lattices have been performed using standard path integral Monte Carlo techniques. Using average plaquette tadpole renormalization scheme, simulations were done with temporal lattice spacings much smaller than the spatial ones and results were obtained for the string tension, the renormalized anisotropy and scalar glueball masses. We find, by comparing the `regular' and `sideways' potentials, that tadpole improvement results in very little renormalization of the bare anisotropy and reduces the discretization errors in the static quark potential and in the glueball masses.

hep-lat↗