Alessandra Feo

Thermodynamics of SU(N) Yang-Mills theories in 2 + 1 dimensions II — The deconfined phase

A bstractWe present a non-perturbative study of the equation of state in the deconfined phase of Yang-Mills theories in D = 2 + 1 dimensions. We introduce a holographic model, based on the improved holographic QCD model, from which we derive a non-trivial relation between the order of the deconfinement phase transition and the behavior of the trace of the energy-momentum tensor as a function of the temperature T. We compare the theoretical predictions of this holographic model with a new set of high-precision numerical results from lattice simulations of SU(N) theories with N = 2, 3, 4, 5 and 6 colors. The latter reveal that, similarly to the D = 3 + 1 case, the bulk equilibrium thermodynamic quantities (pressure, trace of the energy-momentum tensor, energy density and entropy density) exhibit nearly perfect proportionality to the number of gluons, and can be successfully compared with the holographic predictions in a broad range of temperatures. Finally, we also show that, again similarly to the D = 3 + 1 case, the trace of the energy-momentum tensor appears to be proportional to T2 in a wide temperature range, starting from approximately 1.2 Tc, where Tc denotes the critical deconfinement temperature.

Wess-Zumino model with exact supersymmetry on the lattice

A lattice formulation of the four dimensional Wess-Zumino model that uses Ginsparg-Wilson fermions and keeps exact supersymmetry is presented. The supersymmetry transformation that leaves invariant the action at finite lattice spacing is determined by performing an iterative procedure in the coupling constant. The closure of the algebra, generated by this transformation is also showed.

A Model for QCD at High Density and Large Quark Mass

We study the high density region of QCD within an effective model obtained in the frame of the hopping parameter expansion and choosing Polyakov-type loops as the main dynamical variables representing the fermionic matter. To get a first idea of the phase structure, the model is analyzed in strong coupling expansion and using a mean field approximation. In numerical simulations, the model still shows the so-called sign problem, a difficulty peculiar to nonzero chemical potential, but it permits the development of algorithms which ensure a good overlap of the Monte Carlo ensemble with the true one. We review the main features of the model and present calculations concerning the dependence of various observables on the chemical potential and on the temperature, in particular, of the charge density and the diquark susceptibility, which may be used to characterize the various phases expected at high baryonic density. We obtain in this way information about the phase structure of the model and the corresponding phase transitions and crossover regions, which can be considered as hints for the behavior of nonzero density QCD.

Information on the Super Yang-Mills spectrum

We investigate the spectrum of the lightest states of N=1 Super Yang-Mills theory. We first study the spectrum using the recently extended Veneziano Yankielowicz theory containing also the glueball states besides the gluinoball ones. Using a simple Kaehler term we show that within the effective Lagrangian approach one can accommodate either the possibility in which the glueballs are heavier or lighter than the gluinoball fields. We then provide an argument independent from the effective Lagrangian which allows, using information about ordinary QCD, to deduce that the lightest states in Super Yang-Mills theory are the gluinoballs. This helps constraining the Kaehler term of the effective Lagrangian. Using this information and the effective Lagrangian we note that there is a small mixing among the gluinoball and glueball states.

Supersymmetry breaking in two dimensions: The lattice N= 1 Wess-Zumino model

We study dynamical supersymmetry breaking by non perturbative lattice techniques in a class of two-dimensional N=1 Wess-Zumino models. We work in the Hamiltonian formalism and analyze the phase diagram by analytical strong-coupling expansions and explicit numerical simulations with Green Function Monte Carlo methods.

Phase diagram of the lattice Wess-Zumino model from rigorous lower bounds on the energy

We study the lattice

Universal signatures of the effective string in finite temperature lattice gauge theories

N=1

Exact lattice Ward-Takahashi identity for the N=1 Wess-Zumino model

Wess-Zumino model in two dimensions and we construct a sequence

Modeling Equal and Unequal Mass Binary Neutron Star Mergers Using Public Codes

{\ensuremath{\rho}}^{(L)}

Spectral analysis of gravitational waves from binary neutron star merger remnants

of exact lower bounds on its ground-state energy density