arXiv subjects

Nikhil Karthik

Publications and source records attributed to Nikhil Karthik.

42 records · Page 3Linked to original sources

arXiv2015

Phase of the fermion determinant in QED_3 using a gauge invariant lattice regularization

We use canonical formalism to study the fermion determinant in different three dimensional abelian gauge field backgrounds that contain non-zero magnetic and electric flux in order to understand the non-perturbative contributions to the parity-odd and parity-even parts of the phase. We show that a certain phase associated with free fermion propagation along a closed path in a momentum torus is responsible for the parity anomaly in a background with non-zero electric flux. We consider perturbations around backgrounds with non-zero magnetic flux to understand the structure of the parity-breaking perturbative term at finite temperature and mass.

hep-th↗

arXiv2014

The equation of state of two dimensional Yang-Mills theory

We study the pressure, $P$, of SU($N$) gauge theory on a two-dimensional torus as a function of area, $A=l/t$. We find a cross-over scale that separates the system on a large circle from a system on a small circle at any finite temperature. The cross-over scale approaches zero with increasing $N$ and the cross-over becomes a first order transition as $N\to\infty$ and $l\to 0$ with the limiting value of $2Pl/(N-1)t$ depending on the fixed value of $Nl$.

hep-th↗

arXiv2014

The equation of state of QCD at finite chemical potential

We obtain the baryon number density, n, and the excess contribution to the pressure, Delta P, at finite chemical potential, mu_B, and temperature, T, by resumming the Taylor series expansion in a lattice computation with lattice spacing of 1/(4T) and two flavours of quarks at three different quark masses. The method proceeds by giving a critical mu_B and limits on the critical exponent, and permits reliable estimations of the errors in resummed quantities. We find that n and Delta P are insensitive to the quark mass. We also report the bulk isothermal compressibility, kappa, over a range of T and mu_B.

hep-lat↗

arXiv2014

A Concise Force Calculation for Hybrid Monte Carlo with Improved Actions

We present a concise way to calculate force for Hybrid Monte Carlo with improved actions using the fact that changes in thin and smeared link matrices lie in their respective tangent vector spaces. Since hypercubic smearing schemes are very memory intensive, we also present a memory optimized implementation of them.

hep-lat↗

arXiv2013

UV Suppression by Smearing and Screening Correlators

We investigate the mechanism of smearing in the APE, Stout, HYP and HEX schemes through their effect on glue and quark Fourier modes. Using this, we non-perturbatively tune the smearing parameters to their optimum values. Smearing causes a super-linear improvement in taste symmetry breaking in the high temperature phase of QCD. We use optimal smearing in the high temperature phase and find close agreement of meson screening masses with weak coupling predictions.

hep-lat↗

arXiv2013

Hadronic Screening in Improved Taste

We present our results on meson and nucleon screening masses in finite temperature two flavour QCD using smeared staggered valence quarks and staggered thin-link sea quarks with different lattice spacings and quark masses. We investigate optimization of smearing by observing its effects on the infrared (IR) and ultraviolet (UV) components of gluon and quark fields. The application of smearing to screening at finite temperature also provides a transparent window into the mechanism of the interplay of smearing and chiral symmetry. The improved hadronic operators show that above the finite temperature cross over, T_c, screening masses are consistent with weak-coupling predictions. There is also evidence for a rapid opening up of a spectral gap of the Dirac operator immediately above T_c.

hep-lat↗