Finite temperature QCD in the quark-composites approach

We investigate QCD at finite temperature in the quark composites approach, which is based on the use of quark composites with hadronic quantum numbers as fundamental variables. We find that chiral symmetry restoration and quark deconfinement are one and the same first order phase transition, whose critical temperature, in a one loop approximation, is $T= 2\sqrt{\Omega} \rho^{-2}m_{\pi}$, where $m_{\pi}$ is the pion mass, $\Omega=24$ the number of up and down quark components, and $\rho$ a parameter of order 1 whose precise value can be determined by the study of the pion-pion interaction.Comment: LaTex, 5 page

Noncompact Gauge-Invariant Simulations of U(1), SU(2), and SU(3)

We have applied a new gauge-invariant, noncompact, Monte Carlo method to simulate the $U(1)$, $SU(2)$, and $SU(3)$ gauge theories on $8^4$ and $12^4$ lattices. The Creutz ratios of the Wilson loops agree with the exact results for $U(1)$ for $\beta \ge 0.5$ apart from a renormalization of the charge. The $SU(2)$ and $SU(3)$ Creutz ratios robustly display quark confinement at $\beta = 0.5$ and $\beta = 2$, respectively. At much weaker coupling, the $SU(2)$ and $SU(3)$ Creutz ratios agree with perturbation theory after a renormalization of the coupling constant. For $SU(3)$ the scaling window is near $\beta = 2$, and the relation between the string tension $\sigma$ and our lattice QCD parameter $\Lambda_L$ is $\sqrt{\sigma} \approx 5 \Lambda_L$.Comment: For U(1), we switched from beta = 2 / g^2 to beta = 1 / g^2; 3 pages; latex and espcrc2.sty; one figure generated by PiCTeX; our contribution to Lattice '9

From topological to topologically massive gravity through the gauge principle

It is well known that three-dimensional Einstein's gravity without matter is topological, i.e. it does not have local propagating degrees of freedom. The main result of this work is to show that dynamics in the gravitational sector can be induced by employing the gauge principle on the matter sector. This is described by a non-dynamical fermion model that supports a global gauge symmetry. By gauging this symmetry, a vector-spinor field is added to the original action to preserve the local gauge invariance. By integrating out this spin-3/2 field, we obtain a gravitational Chern-Simons term that gives rise to local propagating degrees of freedom in the gravitational sector. This is defined, after the gauging, by topologically massive gravity.Comment: 5 pages, this essay has received an Honorable Mention from the Gravity Research Foundation - 2019 Awards for Essays on Gravitatio

On the Emergent Dynamics of Fermions in Curved Spacetime

Relativistic spin-1/2 particles in curved spacetime are naturally described by Dirac theory, which is a dynamical and Lorentz-invariant field theory. In this work, we propose a non-dynamical fermion theory in 3+1 dimensions dubbed spinor topological field theory, built in terms of a spinor field and a Cartan connection related to de Sitter group. We show that our model gives rise to the Dirac theory in curved spacetime when the local de Sitter gauge invariance of the model breaks down to the Lorentz gauge invariance, providing also a geometric origin to the fermion mass. Finally, we show that other gauge fields and suitable four-fermion interactions can be included in a straightforward way.Comment: 3 pages, published versio