Aspects of Confinement and Chiral Dynamics in 2-d QED at Finite Temperature

We evaluate the Polyakov loop and string tension at zero and finite temperature in $QED_2.$ Using bozonization the problem is reduced to solving the Schr\"odinger equation with a particular potential determined by the ground state. In the presence of two sources of opposite charges the vacuum angle parameter $\theta$ changes by $2\pi (q/e)$, independent of the number of flavors. This, in turn, alters the chiral condensate. Particularly, in the one flavor case through a simple computer algorithm, we explore the chiral dynamics of a heavy fermion.Comment: 4 pages, 2 ps files, uses sprocl.sty. To appear in Proceedings of DPF96 (August, Minnesota

Confinement and Chiral Dynamics in the Multi-flavor Schwinger Model

Two-dimensional QED with $N$ flavor fermions is solved at zero and finite temperature with arbitrary fermion masses to explore QCD physics such as chiral condensate and string tension. The problem is reduced to solving a Schr\"odinger equation for $N$ degrees of freedom with a specific potential determined by the ground state of the Schr\"odinger problem itself.Comment: 9 pages. 3 ps files and sprocl.sty attached. To appear in the Proceedings of the QCD 96 workshop (March, Minnesota

Berezinskii-Kosterlitz-Thouless Transition in Spin-Charge Separated Superconductor

A model for spin-charge separated superconductivity in two dimensions is introduced where the phases of the spinon and holon order parameters couple gauge-invariantly to a statistical gauge-field representing chiral spin-fluctuations. The model is analyzed in the continuum limit and in the low-temperature limit. In both cases we find that physical electronic phase correlations show a superconducting-normal phase transition of the Berezinskii-Kosterlitz-Thouless type, while statistical gauge-field excitations are found to be strictly gapless. The normal-to-superconductor phase boundary for this model is also obtained as a function of carrier density, where we find that its shape compares favorably with that of the experimentally observed phase diagram for the oxide superconductors.Comment: 35 pages, TeX, CSLA-P-93-

Rare top decay and CP violation in THDM

We discuss the formalism of two Higgs doublet model type III with CP violation from CP-even CP-odd mixing in the neutral Higgs bosons. The flavor changing interactions among neutral Higgs bosons and fermions are presented at tree level in this type of model. These assumptions allow the study rare top decays mediated by neutral Higgs bosons, particularly we are interested in $t\rightarrow c l^+l^-$. For this process we estimated upper bounds of the branching ratios $\textrm{Br}(t\rightarrow c \tau^+\tau^-)$ of the order of $10^{-9}\sim 10^{-7}$ for a neutral Higgs boson mass of 125 GeV and $\tan\beta=1$, 1.5, 2, 2.5. For the case of $t\rightarrow c \tau^+\tau^-$ the number of possible events is estimated from 1 to 10 events which could be observed in future experiments at LHC with a luminosity of 300 $\textrm{fb}^{-1}$ and 14 GeV for the energy of the center of mass. Also we estimate that the number of events for the process $t\rightarrow c l^+l^-$ in different scenarios is of order of $2500$.Comment: 8 pages, 5 figure