5,856 research outputs found
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
-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 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
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 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
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