arXiv subjects

Tomoya Hayata

Publications and source records attributed to Tomoya Hayata.

58 records · Page 4Linked to original sources

arXiv2013

Sign problem and the chiral spiral on the finite-density lattice

We investigate the sign problem of the fermion determinant at finite baryon density in (1+1) dimensions, in which the ground state in the chiral limit should be free from the sign problem by forming a chiral spiral. To confirm it, we evaluate the fermion determinant in the continuum theory at the one-loop level and find that the determinant becomes real as expected. The conventional lattice formulation to implement a chemical potential is, however, not compatible with the spiral transformation. We discuss an alternative of the finite-density formulation and numerically verify the chiral spiral on the finite-density lattice.

hep-ph↗

arXiv2013

Time-dependent heavy-quark potential at finite temperature from gauge-gravity duality

The potential between a heavy quark and an anti-quark inside the quark-gluon plasma (QGP) is studied on the basis of the gauge/gravity duality. A real-time complex potential V_{Q\bar{Q}}(t,r) is derived from the Wilson loop with the Euclidean five-dimensional anti-de-Sitter black hole metric. To make the analytic continuation from the imaginary time to the real time, specific variational configurations of the string world sheet in the Euclidean metric are introduced. Rapid approach of V_{Q\bar{Q}}(t,r) to its stationary value is found at the time scale t=1/πT independent of the 't Hooft coupling λ. Also, the imaginary part of V_{Q\bar{Q}}(\infty,r) is found to be significant above the length scale r=1.72/πT independent of λ. Implications of these results to the properties of heavy quarkonia in QGP are briefly discussed.

hep-ph↗

arXiv2013

Dynamical Mass Generation of Vector Mesons from QCD Trace Anomaly

Mass formulas for the light-vector mesons written in terms of the gluon condensate i.e., the trace anomaly in quantum chromodynamics (QCD), are derived on the basis of finite energy QCD sum rules. We utilize sum rules with $s^n$ and $s^{n+1/2}$ weights, which relate the energy-weighted spectral sums to the vacuum expectation values of certain commutation relations. After evaluating the commutation relations, the sum rules with $s^n$ weights are reduced to the familiar ones obtained from the operator product expansion (OPE). On the other hand, the sum rules with $s^{n+1/2}$ weights cannot be derived from OPE. They give new relations between the spectral sums and QCD vacuum fluctuations. To derive simple mass formula, we adopt the pole + continuum Ansatz for the spectral function, and solve coupled equations given by the sum rules with $s^{0,1}$ weights and the new sum rule with $s^{1/2}$ weight. Application of our approach to the axial-vector meson is also discussed.

hep-ph↗

arXiv2010

Rescaled Perturbation Theory

A non-perturbative method which can go beyond the weak coupling perturbation theory is introduced. Essential idea is to formulate a set of exact differential equations as a function of the coupling strength $g$. Unlike other resummation in which information of the higher order terms is necessary, we only need a leading order perturbative formula in every step to reach the large value of $g$. The method is applied to the quantum anharmonic oscillator and quantum double well potential in one dimension. Both are known to have divergent series in the weak coupling perturbation and the latter is not Borel summable. Our method is shown to work well from the weak coupling to the strong coupling for the energy eigenvalues and the wave functions. The method is also applied successfully to the system with time-dependent external field.

quant-ph↗