Fourth Generation Parity

We present a very simple 4th-generation (4G) model with an Abelian gauge interaction under which only the 4G fermions have nonzero charge. The U(1) gauge symmetry can have a Z_2 residual discrete symmetry (4G-parity), which can stabilize the lightest 4G particle (L4P). When the 4G neutrino is the L4P, it would be a neutral and stable particle and the other 4G fermions would decay into the L4P leaving the trace of missing energy plus the standard model fermions. Because of the new symmetry, the 4G particle creation and decay modes are different from those of the sequential 4G model, and the 4G particles can be appreciably lighter than typical experimental bounds.Comment: Version accepted for publication in PR

Bonnor-type Black Dihole Solution in Brans-Dicke-Maxwell Theory

It was originally thought that Bonnor's solution in Einstein-Maxwell theory describes a singular point-like magnetic dipole. Lately, however, it has been demonstrated that indeed it may describe a black {\it dihole}, i.e., a pair of static, oppositely-charged extremal black holes with regular horizons. Motivated particularly by this new interpretation, in the present work, the construction and extensive analysis of a solution in the context of the Brans-Dicke-Maxwell theory representing a black dihole are attempted. It has been known for some time that the solution-generating algorithm of Singh and Rai produces stationary, axisymmetric, charged solutions in Brans-Dicke-Maxwell theory from the known such solutions in Einstein-Maxwell theory. Thus this algorithm of Singh and Rai's is employed in order to construct a Bonnor-type magnetic black dihole solution in Brans-Dicke-Maxwell theory from the known Bonnor solution in Einstein-Maxwell theory. The peculiar feature of the new solution including internal infinity nature of the symmetry axis and its stability issue have been discussed in full detail.Comment: 29 pages, Revtex4, Int. J. Mod. Phys. A (IJMPA), in pres

Vacuum decay and internal symmetries

We study the effects of internal symmetries on the decay by bubble nucleation of a metastable false vacuum. The zero modes about the bounce solution that are associated with the breaking of continuous internal symmetries result in an enhancement of the tunneling rate into vacua in which some of the symmetries of the initial state are spontaneously broken. We develop a general formalism for evaluating the effects of these zero modes on the bubble nucleation rate in both flat and curved space-times.Comment: LaTex, 11 pages, No figures, one minor chang

The Making of the Standard Model

This is the edited text of a talk given at CERN on Septembr 16, 2003, as part of a celebration of the 30th anniversary of the discovery of neutral currents and the 20th anniversary of the discovery of the W and Z particles.Comment: 21 page

Emergence of supersymmetry on the surface of three dimensional topological insulators

We propose two possible experimental realizations of a 2+1 dimensional spacetime supersymmetry at a quantum critical point on the surface of three dimensional topological insulators. The quantum critical point between the semi-metallic state with one Dirac fermion and the s-wave superconducting state on the surface is described by a supersymmetric conformal field theory within $\epsilon$-expansion. We predict the exact voltage dependence of the differential conductance at the supersymmetric critical point.Comment: 8 pages, 2 figures; published versio

Conformal anomaly and the vector coupling in dense matter

We construct an effective chiral Lagrangian for hadrons implemented by the conformal invariance and discuss the properties of nuclear matter at high density. The model is formulated based on two alternative assignment, "naive" and mirror, of chirality to the nucleons. It is shown that taking the dilaton limit, in which the mended symmetry of Weinberg is manifest, the vector-meson Yukawa coupling becomes suppressed and the symmetry energy becomes softer as one approaches the chiral phase transition. This leads to softer equations of state (EoS) and could accommodate the EoS without any exotica consistent with the recent measurement of a $1.97 \pm 0.04\,M_\odot$ neutron star.Comment: v2:10 pages, 2 figures, typos corrected, a rough estimate of m0 adde

SU(2) Chiral Sigma Model Study of Phase Transition in Hybrid Stars

We use a modified SU(2) chiral sigma model to study nuclear matter component and simple bag model for quark matter constituting a neutron star. We also study the phase transition of nuclear matter to quark matter with the mixed phase characterized by two conserved charges in the interior of highly dense neutron stars. Stable solutions of Tolman-Oppenheimer-Volkoff equations representing hybrid stars are obtained with a maximum mass of 1.67$M_{\odot}$ and radius around 8.9 km.Comment: 14 pages, 5 figure

Law, Language, and Forensic Psychiatry

Dr. Thomas Szaz, a controversial figure in psychiatry today, attacks the use of a medical model to explain abnormal behavior. The authors analyze Szaz\u27 views and their implications on the issues of the insanity plea, competency to stand trial, the right to medical treatment, involuntary civil commitment, and victimless crimes

Soft two-meson-exchange nucleon-nucleon potentials. II. One-pair and two-pair diagrams

Two-meson-exchange nucleon-nucleon potentials are derived where either one or both nucleons contains a pair vertex. Physically, the meson-pair vertices are meant to describe in an effective way (part of) the effects of heavy-meson exchange and meson-nucleon resonances. {}From the point of view of ``duality,'' these two kinds of contribution are roughly equivalent. The various possibilities for meson pairs coupling to the nucleon are inspired by the chiral-invariant phenomenological Lagrangians that have appeared in the literature. The coupling constants are fixed using the linear $\sigma$ model. We show that the inclusion of these two-meson exchanges gives a significant improvement over a potential model including only the standard one-boson exchanges.Comment: 21 pages RevTeX, 7 postscript figures; revised version as to appear in Phys. Rev.

Cancellation of soft and collinear divergences in noncommutative QED

In this paper, we investigate the behavior of non-commutative IR divergences and will also discuss their cancellation in the physical cross sections. The commutative IR (soft) divergences existing in the non-planar diagrams will be examined in order to prove an all order cancellation of these divergences using the Weinberg's method. In non-commutative QED, collinear divergences due to triple photon splitting vertex, were encountered, which are shown to be canceled out by the non-commutative version of KLN theorem. This guarantees that there is no mixing between the Collinear, soft and non-commutative IR divergences