On unitarity of a linearized Yang-Mills formulation for massless and massive gravity with propagating torsion

A perturbative regime based on contortion as a dynamical variable and metric as a (classical) fixed background, is performed in the context of a pure Yang-Mills formulation for gravity in a $2+1$ dimensional space-time. In the massless case we show that the theory contains three degrees of freedom and only one is a non-unitary mode. Next, we introduce quadratical terms dependent on torsion, which preserve parity and general covariance. The linearized version reproduces an analogue Hilbert-Einstein-Fierz-Pauli unitary massive theory plus three massless modes, two of them represents non-unitary ones. Finally we confirm the existence of a family of unitary Yang-Mills-extended theories which are classically consistent with Einstein's solutions coming from non massive and topologically massive gravity. The unitarity of these YM-extended theories is shown in a perturbative regime. A possible way to perform a non-perturbative study is remarked.Comment: To appear in International Journal of Modern Physics

Rare top quark decays in extended models

Flavor changing neutral currents (FCNC) decays t to H + c, t to Z + c, and H to t + bar{c} are discussed in the context of Alternative Left-Right symmetric Models (ALRM) with extra isosinglet heavy fermions where FCNC decays may take place at tree-level and are only suppressed by the mixing between ordinary top and charm quarks, which is poorly constraint by current experimental values. The non-manifest case is also briefly discussed.Comment: Contributed talk given at the 10th Mexican Workhop on Particles and Fields, Morelia, Michoacan, Mexico, 7-12 Nov 200

Top quark Chromoelectric and Chromomagnetic Dipole Moments in a Two Higgs Doublet Model with CP violation

In this work we study the anomalous top quark-gluon couplings Chromoelectric Dipole Moment (CEDM) and Chromomagnetic Dipole Moment (CMDM) in a general THDM with CP violation. We find that this model provides an important contribution from the $Y_{tt}$ Yukawa coupling that needs to be taken into account. The CMDM and CEDM obtained are -0.03<\Delta\tilde{k} < 0.005} and $|\Delta \tilde{d}| < 0.005$, respectively.Comment: 9 Pages, 2 tables, 4 figure

2D massless QED Hall half-integer conductivity and graphene

Starting from the photon self-energy tensor in a magnetized medium, the 3D complete antisymmetric form of the conductivity tensor is found in the static limit of a fermion system $C$ non-invariant under fermion-antifermion exchange. The massless relativistic 2D fermion limit in QED is derived by using the compactification along the dimension parallel to the magnetic field. In the static limit and at zero temperature the main features of quantum Hall effect (QHE) are obtained: the half-integer QHE and the minimum value proportional to $e^2/h$ for the Hall conductivity . For typical values of graphene the plateaus of the Hall conductivity are also reproduced.Comment: 14 pages, 2 figure