D.L. Boyda

New approach to canonical partition functions computation in

We propose and test a new approach to computation of canonical partition functions in lattice QCD at finite density. We suggest a few steps procedure. We first compute numerically the quark number density for imaginary chemical potential

N_f=2

imu_{qI}

lattice QCD at finite baryon density

. Then we restore the grand canonical partition function for imaginary chemical potential using fitting procedure for the quark number density. Finally we compute the canonical partition functions using high precision numerical Fourier transformation. Additionally we compute the canonical partition functions using known method of the hopping parameter expansion and compare results obtained by two methods in the deconfining as well as in the confining phases. The agreement between two methods indicates the validity of the new method. Our numerical results are obtained in two flavor lattice QCD with clover improved Wilson fermions.

Lattice Study of QCD Phase Structure by Canonical Approach

We investigate the potential for using the canonical ensemble approach to determine the QCD phase diagram in the temperature - density plane. This approach allows us to study the finite baryon density regions where the well-known sign problem obstructs the standard lattice QCD numerical study. Using the canonical ensemble approach, we perform lattice QCD simulations at the pure imaginary quark chemical potential. In this case no sign problem occurs. We then calculate physical quantities at the real chemical potential through the canonical partition functions. nIn this approach, the canonical partition functions,

Novel approach to deriving the canonical generating functional in lattice QCD at a finite chemical potential

Z_n

Restoring canonical partition functions from imaginary chemical potential

, play an essential role for mapping the information from the pure imaginary chemical potential values to the real ones. We analyze how inaccuracies in the numerical data obtained at the imaginary chemical potential affect the results for the real values, where the QCD predictions confront experimental quark-gluon plasma (QGP) data. nWe compute the higher moments of the baryon number including the kurtosis and compare our results with information from relativistic heavy-ion collisions.

Lattice QCD at finite baryon density using analytic continuation

A novel approach to the problem of deriving the generating functional for the canonical ensemble in lattice QCD at a nonzero chemical potential is proposed. The derivation proceeds in several steps. First, the baryon density for imaginary values of the chemical potential is obtained. Then, again for imaginary values of the chemical potential, the generating functional of the grand canonical ensemble is derived. In this analysis, a fit of baryon density is employed toward simplifying the procedure of numerical integration. Finally, the generating potential for the canonical ensemble is derived using a high-precision numerical Fourier transform. The generating functional for the canonical ensemble is also derived using the known hopping-parameter expansion, and the results obtained with the two methods are compared for the deconfinement phase in the lattice QCD with two flavors.

Study of lattice QCD at finite baryon density using the canonical approach

Using GPGPU techniques and multi-precision calculation we developed the code to study QCD phase transition line in the canonical approach. The canonical approach is a powerful tool to investigate sign problem in Lattice QCD. The central part of the canonical approach is the fugacity expansion of the grand canonical partition functions. Canonical partition functions

Study of lattice QCD at finite chemical potential using the canonical ensemble approach

Z_n(T)

Sign problem in finite density lattice QCD

are coefficients of this expansion. Using various methods we study properties of