title:
On the Possibility of Second-Order Phase Transitions in Spontaneously
  Broken Gauge Theories

abstract:
  In the ``Type-II'' regime, $m_{\rm Higgs}\gap m_{\rm gauge}$, the
finite-temperature phase transition in spontaneously-broken gauge theories
(including the standard model) must be be studied using a renormalization group
treatment. Previous studies within the $(4-\ep)$-expansion suggest a 1st-order
transition in this regime. We use analogies with experimentally accessible
phase transitions in liquid crystals, and theoretical investigations of
superconductor phase transitions to argue that, in this range, the critical
behavior of a large class of gauge-Higgs-fermion systems changes from 1st to
2nd-order as a function of Higgs mass. We identify a set of models which,
within the $(2+\ep)$-expansion, possess fixed points that can describe this
2nd-order behavior. As usual, a definitive demonstration that the claimed
critical behavior occurs (and a reliable estimate of $m_{\rm Higgs}$ at the
tricritical point) will probably require numerical simulations. This paper uses
the ``phyzzx'' macro package. To obtain figure contact the author.


title: Multiple photon effects in $pp$ scattering at SSC energies

abstract:
  The Monte Carlo program SSCYFS2 is used in conjunction with available parton
distribution functions to calculate the effects of multiple photon radiation on
pp scattering at SSC energies. Effects relevant to precision SSC physics such
as Higgs discovery and exploration are illustrated.


title: Density Perturbations,Gravity Waves and the Cosmic Microwave Background

abstract:
  We asses the contribution to the observed large scale anisotropy of the
cosmic microwave background radiation, arising from both gravity waves as well
as adiabatic density perturbations, generated by a common inflationary
mechanism in the early Universe.
  We find that for inflationary models predicting power law primordial spectra
%$a(t) \propto t^p, p > 1$, $\dk^2 \propto k^n$, the relative contribution to
the quadrupole anisotropy from gravity waves and scalar density perturbations,
depends crucially upon $n$. For $n < 0.87$, gravity waves perturb the CMBR by a
larger amount than density perturbations, whereas for $n > 0.87$ the reverse is
true. %For nearly exponential inflation, on the other hand, the contribution to
the %microwave anisotropy from scalar density perturbations always exceeds
%that due to gravity waves. Normalising the amplitude of the density
perturbation spectrum at large scales, using the observed value of the COBE
quadrupole, we determine $(\delta M /M)_{16}$ -- the rms density contrast on
scales $\sim 16 h_{50}^{-1}$ Mpc, for cosmological models with cold dark
matter. We find that for $n < 0.75$, a large amount of biasing is required in
order to reconcile theory with observations.


title: On the Stability of Electroweak Strings (New Version)

abstract:
  We map the parameter space that leads to stable Z-vortices in the electroweak
model. For $sin^2 \theta_W = 0.23$, we find that the strings are unstable for a
Higgs mass larger than 24 GeV. Given the latest constraints on the Higgs mass
from LEP, this shows that, if the standard electroweak model is realized in
Nature, the Z-vortex (in the bare model) is unstable.


title: Quantum effects near a point mass in 2+1 dimensional gravity

abstract:
  We investigate the behaviour of classical and quantum fields in the conical
space-time associated with a point mass in 2+1 dimensions. We show that the
presence of conical boundary conditions alters the electrostatic field of a
point charge leading to the presence of a finite self-force on the charge from
the direction of the point mass exactly as if the point mass itself were
charged. The conical space-time geometry also affects the zero point
fluctuations of a quantum scalar field leading to the existence of a vacuum
polarisation --- $\langle T_\mn \rangle$, in the 2+1 dimensional analog of the
Schwarzschild metric. The resulting linearised semi-classical Einstein
equations --- $G_\mn = 8 \pi G \langle T_\mn \rangle$, possess a well defined
Newtonian limit, in marked contrast to the classical case for which no
Newtonian limit is known to exist. An elegant reformulation of our results in
terms of the method of images is also presented.
  Our analysis also covers the non-static de Sitter--Schwarzschild metric in
2+1 dimensions, in which in addition to the vacuum polarisation, a non-zero
vacuum flux ofenergy -- $\langle T_{rt} \rangle $ is also found to exist.As
part of this analysis, we evaluate the scalar field propagator in an
$n$-dimensional de Sitter space,


title:
Study of gamma gamma -> W_L W_L and gamma gamma -> Z_L Z_L reactions
  with Chiral Lagrangians

abstract:
  We analyze the effects of a strongly interacting symmetry breaking sector of
the Standard Model in $\gamma \gamma -> W_L^+ W_L^-$ and $\gamma \gamma -> Z_L
Z_L$ reactions at TeV energies by using Chiral Lagrangians and Chiral
Perturbation Theory. We find significant deviations from the Standard Model
predictions for the differential cross sections at high invariant mass of the
gauge bosons pair. We study the experimental signals that could be obtained in
a high energy and high luminosity dedicated $\gamma\gamma$ collider and
estimate the sensitivity that such experiments could reach to the values of the
effective lagrangian parameters.


title: Properties of Baryons Containing a Heavy Quark in the Skyrme Model

abstract:
  The properties of baryons containing one heavy quark are studied in the
Skyrme model, where they are treated as bound states of a heavy meson with an
$SU(2)$ chiral soliton. In the large $N_c$ limit, the baryon spectrum is an
infinite tower of degenerate states with isospin and spin of the light degrees
of freedom $I=s_\ell=0,1,2,\dots$, and total spin $s=\abs{s_\ell\pm1/2}$.
Exotic states with no quark model analogues in the large $N_c$ limit are found
to be unbound. The $\Sigma_c-\Lambda_c$ mass difference is computed and found
to be in good agreement with experiment. The $\Sigma_c\,\Sigma_c\,\pi$ and
$\Sigma_c\,\Lambda_c\,\pi$ coupling constants are calculated to leading order
in $N_c$ in terms of $g_A$, the axial coupling constant of the nucleon. We
discuss the extension of our results to $SU(3)$ chiral solitons.


title: Quaternions and the heuristic role of mathematical structures in physics

abstract:
  One of the important ways development takes place in mathematics is via a
process of generalization. On the basis of a recent characterization of this
process we propose a principle that generalizations of mathematical structures
that are already part of successful physical theories serve as good guides for
the development of new physical theories. The principle is a more formal
presentation and extension of a position stated earlier this century by Dirac.
Quaternions form an excellent example of such a generalization, and we consider
a number of the ways in which their use in physical theories illustrates this
principle.


title: Neutrino Helioseismology

abstract:
  The observed deficit of $\rm ^8B$ solar neutrinos may call for an improved
standard model of the sun or an expanded standard model of particle physics
({\it e.g.,} with neutrino masses and mixing). In the former case, contemporary
fluid motions and thermal fluctuations in the sun's core may modify nuclear
reaction rates and restore agreement. To test this notion, we propose a search
for short--term variations of the solar neutrino flux.


title: Calculating the Critical Temperature for Coleman-Weinberg GUTs

abstract:
  We study the finite temperature effective potential of the Higgs scalar in
GUTs with Coleman-Weinberg symmetry breaking. The critical temperature is
derived without employing a high temperature approximation to the effective
potential, and the limitations of such approximations are discussed.


title:
Two- and Three Vector Boson Production in e+ e- Collisions within the
  BESS Model

abstract:
  The BESS model is the Higgsless alternative to the standard model of
electroweak interaction with nonlinear realized spontaneous symmetry breaking.
Since it is non-renormalizable new couplings (not existing in the SM) are
induced at each loop order. On the basis of the one loop induced gauge boson
self-couplings we calculated the cross sections for the two and three gauge
boson production processes in $e^+e^-$ collisions. Measurements of these cross
sections in a planned $e^+e^-$ linear collider at $\sqrt s = 500 GeV$ (NLC)
will supply a good empirical test of the gauge boson self interactions and thus
should enable to discriminate between SM and its alternatives (BESS).


title: Higgs boson bounds in non-minimal supersymmetric standard models

abstract:
  In the minimal supersymmetric standard model (MSSM), when radiative
corrections are included, the mass of the $CP=+1$ lightest Higgs boson is
bounded by $\sim 110\ GeV$ for $m_t < 150\ GeV$ and a scale of supersymmetry
breaking $\sim\ 1\ TeV$. In non-minimal supersymmetric standard models (NMSSM)
upper bounds on the mass of the corresponding scalar Higgs boson arise if the
theory is required to remain perturbative up to scales $\gg G_F^{-1/2}$. We
have computed those bounds for two illustrative NMSSM: i) A model with an
arbitrary number of gauge singlets; ii) A model with three $SU(2)_L$ triplets
with $Y=0,\pm 1$. We have integrated numerically the corresponding
renormalization group equations (RGE), including the top and bottom quark
Yukawa couplings, and added one-loop radiative corrections. For $m_t > 91\ GeV$
the absolute bounds are $\sim 140\ GeV$ for both models.


title: Two Stage Phase Transition in Two Higgs Models

abstract:
  We present a mechanism in which models with two Higgs fields can undergo a
two stage phase transition as the temperature falls. The first stage is a
conventional second order (or weakly first order) transition in which the
symmetry is broken. Shortly thereafter follows a first order transition with
barrier penetration, bubble production and loss of thermal equilibrium. For
Higgs potentials with CP violation, we show that the second stage of the
transition has all the features required for weak scale baryogenesis.


title: Prospect of Heavy Right-Handed Neutrino Search at SSC/LHC Energies

abstract:
  Right-handed neutrinos with large Majorana mass occur naturally in the
left-right symmetric model. We explore the prospect of such heavy Right-handed
Neutrino search Via $W_R$ decay in the Like Sign Dilepton channel at SSC/LHC.
The standard model background can be effectively eliminated by suitable lepton
$p_T$ and isolation cuts without affecting the signal cross section seriously.
In this way it seems possible to explore the bulk of the parameter space $0 <
M_{N_R} < M_{W_R}$, with $M_{W_R}$ going upto 3000 (2000) GeV at SSC (LHC)
energy.


title: Decay of the Z Boson into Scalar Particles

abstract:
  In extensions of the standard model, light scalar particles are often
possible because of symmetry considerations. We study the decay of the Z boson
into such particles. In particular, we consider for illustration the scalar
sector of a recently proposed model of the 17-keV neutrino which satisfies all
laboratory, astrophysical, and cosmological constraints.


title: Planck scale effects in neutrino physics

abstract:
  We study the phenomenology and cosmology of the Majoron (flavon) models of
three active and one inert neutrino paying special attention to the possible
(almost) conserved generalization of the Zeldovich-Konopinski-Mahmoud lepton
charge. Using Planck scale physics effects which provide the breaking of the
lepton charge, we show how in this picture one can incorporate the solutions to
some of the central issues in neutrino physics such as the solar and
atmospheric neutrino puzzles, dark matter and a 17 keV neutrino. These
gravitational effects induce tiny Majorana mass terms for neutrinos and
considerable masses for flavons. The cosmological demand for the sufficiently
fast decay of flavons implies a lower limit on the electron neutrino mass in
the range of 0.1-1 eV.


title: Critical Behavior in the Electroweak Phase Transition

abstract:
  We examine the behavior of the standard-model electroweak phase transition in
the early Universe. We argue that close to the critical temperature it is
possible to estimate the {\it effective} infrared corrections to the 1-loop
potential using well known $\varepsilon$-expansion results from the theory of
critical phenomena in 3 spatial dimensions. The theory with the
$\varepsilon$-corrected potential exhibits much larger fluctuations in the
spatial correlations of the order parameter, considerably weakening the
strength of the transition.


title:
Effects of Collective Potentials on Pion Spectra in Relativistic Heavy
  Ion Collisions

abstract:
  The effect of collective potentials on pion spectra in ultrarelativistic
heavy ion collisions is investigated. We find the effect of these potential to
be very small, too small to explain the observed enhancement at low transverse
momenta. (7 figures, bill be send on request)


title:
The Cosmological Kibble Mechanism in the Laboratory: String Formation in
  Liquid Crystals

abstract:
  We have observed the production of strings (disclination lines and loops) via
the Kibble mechanism of domain (bubble) formation in the isotropic to nematic
phase transition of a sample of uniaxial nematic liquid crystal. The probablity
of string formation per bubble is measured to be $0.33 \pm 0.01$. This is in
good agreement with the theoretical value $1/ \pi$ expected in two dimensions
for the order parameter space $S^2/{\bf Z}_2$ of a simple uniaxial nematic
liquid crystal.


title: On the Infrared Behavior of the Pressure in Thermal Field Theories

abstract:
  We study non-perturbatively, via the Schwinger-Dyson equations, the leading
infrared behavior of the pressure in the ladder approximation. This problem is
discussed firstly in the context of a thermal scalar field theory, and the
analysis is then extended to the Yang-Mills theory at high temperatures. Using
the Feynman gauge, we find a system of two coupled integral equations for the
gluon and ghost self-energies, which is solved analytically. The solutions of
these equations show that the contributions to the pressure, when calculated in
the ladder approximation, are finite in the infrared domain.


title: E6 GUT and Large Neutrino Mixing

abstract:
  All experimental results concerning possible neutrino oscillations are
naturally and simultaneously accounted for in an $E_6$ GUT model. The fermionic
mass matrices are dictated by the symmetry breaking and specific radiative
corrections and not by the use of ``Ans\"atze'' or discrete symmetries.


title: The Generational Seesaw Mechanism in [SU(6)]$^{3}\times$Z$_{3}$}

abstract:
  In the context of the left-right symmetric gauge group [SU(6)]$^3\times$
Z$_3$ which unifies nongravitational forces with flavors, we analyze the
generational seesaw mechanism. At tree level we get
m$_{\nu_\tau}\sim$m$_{\nu_\mu}\sim$M$^2_L$/M$_H$, m$_{\nu_e}=0$, where
M$_L\sim10^2$ GeVs and M$_H\ge 100$ TeVs is the mass scale at which the
horizontal interactions get spontaneously broken. The right handed neutrinos
get a Majorana mass M$_R\gg $M$_H$ of the order of the scale where SU(2)$_R$ is
broken. An exotic neutral lepton with a mass of the order of M$^2_H$/M$_R$ is
predicted. First order radiative corrections will produce m$_{\nu_e}\neq0$
which is at least two orders of magnitude smaller than the other two neutrino
masses.


title:
Renormalization Group Coefficients for the Un-Truncated Derivative
  Expansion in Effective Field Theory

abstract:
  We investigate the renormalization of ``nonlocal" interactions which arise as
an infinite sum of higher derivative interactions in an effective field theory.
Using dimensional regularization with minimal subtraction in a general scalar
field theory, we write an integro-differential renormalization group equation
for the most general graph at one loop order.


title:
Hyperfine Splittings of Baryons Containing a Heavy Quark in the Skyrme
  Model

abstract:
  The $\Sigma_c^*-\Sigma_c$ and $\Sigma_b^*-\Sigma_b$ hyperfine mass splittings
are computed in the Skyrme model. The hyperfine splittings are suppressed by
both $1/N_c$ and by $1/m_Q$, where $N_c$ is the number of colors and $m_Q$ is
the mass of the heavy quark. The $\Sigma_c$, $\Sigma_c^*$, $\Sigma_b$,
$\Sigma_b^*$, and $\Lambda_b$ masses are predicted in terms of the known values
of the $\Lambda_c$, $D$, $D^*$, $B$ and $B^*$ masses.


title:
Large- and Small-Scale Constraints on Power Spectra in $\Omega=1$
  Universes

abstract:
  The cold dark matter (CDM) model of structure formation, normalized on large
scales, leads to excessive pairwise velocity dispersions on small scales. In an
attempt to circumvent this problem, we study three scenarios (all with
$\Omega=1$) which have more large-scale power and less small-scale power than
the CDM model: 1) an admixture of cold and hot dark matter; 2) cold dark matter
with a non-scale-invariant, power-law primordial power spectrum; and 3) cold
dark matter with coupling of dark matter to a long-range vector field. Despite
the {reduced} small-scale power, when such models are evolved in the nonlinear
regime to large amplitude, the velocities on small scales are actually {\it
increased} over CDM with the same value of $\sigma_8$. This `flip-over', in
disagreement with the expectation from linear perturbation theory, arises from
the nonlinear coupling of the extra power on large scales with shorter
wavelengths. However, due to the extra large-scale power, the recent COBE DMR
results indicate smaller amplitudes for these models, $\sigma_8 \sim 0.5 -
0.7$, than for CDM (for which $\sigma_8 \sim 1.2$). Therefore, when normalized
to COBE on large scales, such models do lead to reduced velocities on small
scales and they produce fewer halos compared with CDM. Quantitatively it seems,
however, that models that produce sufficiently low small-scale velocities fail
to produce an adequate distribution of halos.


title: On the QCD corrections to the charged Higgs decay of a heavy quark

abstract:
  Using dimensional regularization for both infrared and ultraviolet
divergences, we confirm that the QCD corrections to the decay width
$\Gamma(t\to H^+b)$ are equal to those to $\Gamma(t\to W^+b)$ in the limit of a
large $t$ quark mass.


title: Solar Neutrinos with Three Flavor Mixings

abstract:
  The recent 71Ga solar neutrino observation is combined with the 37Cl and
Kamiokande-II observations in an analysis for neutrino masses and mixings. The
allowed parameter region is found for matter enhanced mixings among all three
neutrino flavors. Distortions of the solar neutrino spectrum unique to three
flavors are possible and may be observed in continuing and next generation
experiments.


title:
Composite Vector Leptoquarks in $e^+ e^-$, $\gamma e$, and
  $\gamma\gamma$ Colliders

abstract:
  We study the signals for composite vector leptoquarks in $e^+ e^-$ colliders
(LEP II, NLC, and CLIC) through their effects on the production of jet pairs,
as well as their single and pair productions. We also analyze their production
in $\gamma e$ and $\gamma\gamma$ collisions.


title: Neutrino masses and mixings in a predictive theory of fermion masses

abstract:
  A framework for predicting charged fermion masses in supersymmetric grand
unified theories is extended to make predictions in the neutrino sector. Eight
new predictions are made, and their relevance to neutrino oscillation
experiments and the solar neutrino problem are discussed.


title: Heavy Hadron Chiral Perturbation Theory

abstract:
  The formalism and applications of chiral perturbation theory for hadrons
containing a single heavy quark are discussed. We emphasize the utility of
working directly with the velocity dependent ``super'' fields which appear in
the chiral Lagrangian and whose interactions manifestly preserve heavy quark
spin symmetry rather than their individual spin components. Chiral logarithm
corrections to meson and baryon Isgur-Wise functions are found using these
fields.
  We also identify a unique dimension-five operator which couples the axial
vector Goldstone current to the heavy antitriplet baryon field $T_\Q$. We then
compute the differential rate for the spin symmetry violating decay $T_b(v) \to
T_c(v') \ell \bar{\v}_\ell \pi$. The ratio of this decay rate to that for the
corresponding pure semileptonic transition can be studied away from the zero
recoil point.


title: Metastable Cosmic Strings in Realistic Models

abstract:
  We investigate the stability of the electroweak Z-string at high
temperatures. Our results show that while finite temperature corrections can
improve the stability of the Z-string, their effect is not strong enough to
stabilize the Z-string in the standard electroweak model. Consequently, the
Z-string will be unstable even under the conditions present during the
electroweak phase transition. We then consider phenomenologically viable models
based on the gauge group $SU(2)_L \times SU(2)_R \times U(1)_{B-L}$ and show
that metastable strings exist and are stable to small perturbations for a large
region of the parameter space for these models. We also show that these strings
are superconducting with bosonic charge carriers. The string superconductivity
may be able to stabilize segments and loops against dynamical contraction.
Possible implications of these strings for cosmology are discussed.


title:
Gravitationally Induced Scalar Field Fluctuations in the Radiation
  Dominated R-W Universe

abstract:
  It is shown that quantum fluctuations due to a nontrivial gravitational
background in the flat radiation dominated universe can play an important
cosmological role generating nonvanishing cosmological global charge, e.g.
baryon number, asymmetry. The explicit form of the fluctuations at vacuum and
at finite temperature is given. Implications for particle physics are
discussed.


title: COBE vs Cosmic Strings: An Analytical Model

abstract:
  We construct a simple analytical model to study the effects of cosmic strings
on the microwave background radiation. Our model is based on counting random
multiple impulses inflicted on photon trajectories by the string network
between the time of recombination and today. We construct the temperature
auto-correlation function and use it to obtain the effective power spectrum
index n, the rms-quadrupole-normalized amplitude $Q_{rms-PS}$ and the rms
temperature variation smoothed on small angular scales. For the values of the
scaling solution parameters obtained in Refs.\cite{bb90},\cite{as90} we obtain
$n=1.14 \pm 0.5$, $Q_{rms-PS}=(4.5\pm 1.5) G\mu$ and $({{\Delta T}\over
T})_{rms}=5.5 G\mu$. Demanding consistency of these results with the COBE data
leads to $G\mu=(1.7 \pm 0.7)\times 10^{-6}$ (where $\mu$ is the string mass per
unit length), in good agreement with direct normalizations of $\mu$ from
observations.


title: The Baryon Isgur-Wise Function in the Large $N_c$ Limit

abstract:
  In the large $N_c$ limit, the $\Lambda_b$ and $\Lambda_c$ can be treated as
bound states of chiral solitons and mesons containing a heavy quark. We show
that the soliton and heavy meson are bound in an attractive harmonic oscillator
potential. The Isgur-Wise function for $\Lambda_b\rightarrow\Lambda_c\,
e^-\,\bar\nu_e$ decay is computed in the large $N_c$ limit. Corrections to the
form factor which depend on $m_N/ m_Q$ can be summed exactly ($m_N$ and $m_Q$
are the nucleon and heavy quark masses). We find that this symmetry breaking
correction at zero recoil is only $1\%$.


title: Large Jets at Hadron Colliders at Order $\alpha_s^3$: A Look Inside

abstract:
  Results from the study of hadronic jets in hadron-hadron collisions at order
$\alpha_s^3$ in perturbation theory are presented. The focus is on various
features of the internal structure of jets. The numerical results of the
calculation are compared with data where possible and exhibit reasonable
agreement.


title:
Spin-Spin Asymmetries in Large Transverse Momentum Higgs Boson
  Production

abstract:
  We examine the spin-dependence of standard model Higgs boson production at
large transverse momentum via the processes $gg \rightarrow gH^0$, $qg
\rightarrow qH^0$, and $q\overline{q} \rightarrow gH^0$. The partonic level
spin-spin asymmetries ($\hat{a}_{LL}$) for these processes are large at SSC/LHC
energies.


title: Coannihilation Effects and Relic Abundance of Higgsino-Dominant LSPs

abstract:
  We calculate the relic abundance of Higgsino-dominant lightest
superparticles, taking account of coannihilations with the superparticles which
are almost degenerate with the lightest one. We show that their relic abundance
is reduced drastically by the coannihilation processes and hence they are
cosmologically of no interest.


title:
The structure of the pion and effective electroweak currents in soliton
  models of the nucleon

abstract:
  Nonminimal substitution terms in electroweak currents are studied in
effective chiral soliton models. It is found that the terms describing the
structure of the pion lead to sizable effects in form factors and
polarizabilities of the nucleon.


title:
The role of the Delta isobar in chiral perturbation theory and hedgehog
  soliton models

abstract:
  Hedgehog model predictions for the leading nonanalytic behavior (in
$m^{2}_{\pi }$) of certain observables are shown to agree with the predictions
of chiral perturbation theory up to an overall factor which depends on the
operator. This factor can be understood in terms of contributions of the
$\Delta$ isobar in chiral loops. These physically motivated contributions are
analyzed in an expansion in which both $m_{\pi}$ and $M_{\Delta}-M_N$ are taken
as small parameters, and are shown to yield large corrections to both hedgehog
models and chiral perturbation theory.


title: P-Wave Charmonium Production in B-Meson Decays

abstract:
  We calculate the decay rates of $B$ mesons into P-wave charmonium states
using new factorization formulas that are valid to leading order in the
relative velocity of the charmed quark and antiquark and to all orders in the
running coupling constant of QCD. We express the production rates for all four
P states in terms of two nonperturbative parameters, the derivative of the
wavefunction at the origin and another parameter related to the probability for
a charmed-quark-antiquark pair in a color-octet S-wave state to radiate a soft
gluon and form a P-wave bound state. Using existing data on $B$ meson decays
into $\chi_{c1}$ to estimate the color-octet parameter, we find that the
color-octet mechanism may account for a significant fraction of the $\chi_{c1}$
production rate and that $B$ mesons should decay into $\chi_{c2}$ at a similar
rate.


title: Searching for TeV dark matter by atmospheric Cerenkov techniques

abstract:
  There is a growing interest in the possibility that dark matter could be
formed of weakly interacting particles with a mass in the 100 GeV - 2 TeV
range, and supersymmetric particles are favorite candidates. If they constitute
the dark halo of our Galaxy, their mutual annihilations produce energetic gamma
rays that could be detected using existing atmospheric \u{C}erenkov techniques.


title:
Response of nucleons to external probes in hedgehog models: I.
  Electromagnetic polarizabilities

abstract:
  Electromagnetic polarizabilities of the nucleon are analyzed in a hedgehog
model with quark and meson degrees of freedom.


title:
Response of nucleons to external probes in hedgehog models: II. General
  formalism

abstract: Linear response theory for SU(2) hedgehog soliton models is developed.


title: Parton-Hadron duality in event generators

abstract:
  The validity of local parton-hadron duality within the framework of HERWIG
and JETSET event generators is investigated. We concentrate on ${\rm e}^{+}{\rm
e}^{-}$ annihilations in LEP 2 energy range as these interactions provide
theoretically the cleanest condition for the discussion of this concept.


title: Extended Technicolor Corrections to the $Z b\bar b$ Vertex

abstract:
  Extended technicolor theories generate potentially large corrections to the
$\Zbb$ vertex. These can be observed in current experiments at LEP.


title: Bounds on mini-charged neutrinos in the minimal standard model

abstract:
  In the minimal Standard Model (MSM) with three generations of quarks and
leptons, neutrinos can have tiny charges consistent with electromagnetic gauge
invariance. There are three types of non-standard electric charge, given by
$Q_{st} + \epsilon(L_i - L_j)$, where $i, j = e, \mu, \tau$ $(i \neq j)$,
$Q_{st}$ is standard electric charge, $L_i$ is a family-lepton--number, and
$\epsilon$ is an arbitrary parameter which is put equal to zero in the usual
incarnation of the MSM. These three non-standard electric charges are of
considerable theoretical interest because they are compatible with the MSM
Lagrangian and $SU(3)_c \otimes SU(2)_L \otimes U(1)_Y$ gauge anomaly
cancellation. The two most conspicuous implications of such non-standard
electric charges are the presence of two generations of massless charged
neutrinos and a breakdown in electromagnetic universality for $e$, $\mu$ and
$\tau$. We use results from (i) charge conservation in $\beta$-decay, (ii)
physical consequences of charged atoms in various contexts, (iii) the anomalous
magnetic moments of charged leptons, (iv) neutrino-electron scattering, (v)
energy loss in red giant and white dwarf stars, and (vi) limits on a
cosmologically induced thermal photon mass, to place bounds on $\epsilon$.
While the constraints derived for $\epsilon$ 10^{-21}$), the $L_{\mu}-L_{\tau}$
case allows $\epsilon$ to be as large as $10^{-14}$.


title: Bilocal Field Approach and Semileptonic Heavy Meson Decays

abstract:
  In this paper we consider the bilocal field approach for $QCD$. We obtain a
bilocal effective meson action with a potential kernel given in relativistic
covariant form. The corresponding Schwinger--Dyson and Bethe--Salpeter
equations are investigated in detail. By introducing weak interactions into the
theory we study heavy meson properties as decay constants and semileptonic
decay amplitudes. Thereby, the transition from the bilocal field description to
the heavy quark effective theory is discussed. Considering as example the
semileptonic decay of a pseudoscalar $B$--meson into a pseudoscalar $D$--meson
we obtain an integral expression for the corresponding Isgur--Wise function in
terms of meson wave functions.


title: New Neutrino Physics Without Fine Tuning

abstract:
  We show how a 17 keV neutrino, the solar neutrino problem, and the
atmospheric muon-neutrino deficit could all be the low-energy residues of the
same pattern of lepton-number breaking at and above the weak scale, with no
requirement for fine-tuning a symmetry-breaking scale at lower energies. Talk
given at ``Beyond the Standard Model III'', Carleton University, June 1992.


title:
Minimal Supersymmetric Standard Model Extended by One Additional Higgs
  Singlet and its Influence on the Anomalous Magnetic Moment of the Muon

abstract:
  We present the results of the influence of the minimal supersymmetric
standard model extended by an additional
  Higgs singlet N, with vacuum expectation value $v_N$, on the anomalous
magnetic moment of the muon.
  This gives different mass matrices for the charginos and neutralinos, which
are taken into account within the relevant penguin diagrams leading to a
contribution $\Delta a_{\mu}$\ to the anomalous magnetic moment of the muon. We
show that a large vacuum expectation value for the Higgs singlet leads to a
suppression of the supersymmetric contribution making it difficult to see in an
experiment in the near future.}\hfill


title: Compact Lattice QED and the Coulomb Potential

abstract:
  The potential energy of a static charge distribution on a lattice is
rigorously computed in the standard compact quantum electrodynamic model. The
method used follows closely that of Weyl for ordinary quantum electrodynamics
in continuous space-time. The potential energy of the static charge
distribution is independent of temperature and can be calculated from the
lattice version of Poisson's equation. It is the usual Coulomb potential.


title: Summing tree graphs at threshold

abstract:
  The solution of the classical field equation generates the sum of all tree
graphs. We show that the classical equation reduces to an easily solved
ordinary differential equation for certain multiparticle threshold amplitudes
and compute these amplitudes.


title:
Electromagnetic Polarisability of the Nucleon in Chiral Perturbation
  Theory

abstract:
  We compute the polarisability of the nucleon to leading order in chiral
perturbation theory. The contributions from kaons and baryon resonances as
intermediate states are included in addition to the contribution from pions and
nucleons that had been previously computed. The isoscalar operators are
dominated by the infrared behaviour of pion loops giving rise to a $1/m_{\pi}$
coefficient. In contrast, the isovector operators are dominated by loops
involving kaons, giving a $1/m_{k}$ coefficient, and further demonstrates that
the strange quark is an important component of the nucleon. In addition, the
inclusion of the decuplet of baryon resonances as intermediate states
substantially modifies the result found from the octet baryons alone for the
isoscalar polarisability.


title: Total cross sections

abstract:
  Regge theory provides a very simple and economical description of all total
cross sections


title:
17 keV neutrino and large magnetic moment solution of the solar neutrino
  puzzle

abstract:
  Zee-type models with Majorons naturally incorporate the 17 keV neutrino but
in their minimal version fail to simultaneously solve the solar neutrino
puzzle. If there is a sterile neutrino state, we find a particularly simple
solution to the solar neutrino problem, which besides $\nu_{17}$ predicts a
light Zeldovich-Konopinski-Mahmoud neutrino $\nu_{light}=\nu_e+\nu_{\mu}^c$
with a magnetic moment being easily as large as $10^{-11}\mu_B$ through the
Barr-Freire-Zee mechanism.


title:
The Production of $Z'$ Associated With Photons or Jets as a Probe of New
  Gauge Boson Couplings

abstract:
  We examine the production of a new $Z'$ gauge boson in association with
photons or jets at future hadron supercolliders as a probe of its couplings to
fermions. Associated jet production is found to be rather insensitive to these
couplings and suffers from large uncertainties as well as substantial
backgrounds. On the other hand, the ratio of rates for associated photon $Z'$
production to that of conventional $Z'$ production has a rather clean signature
(once appropriate cuts are made), and is found to be quite sensitive to the
choice of extended electroweak model, while being simultaneously insensitive to
structure function uncertainties and QCD corrections. Rates at both the SSC and
LHC are significant for $Z'$ masses in the 1 TeV range.


title: Discrete Gauge Symmetries in Axionic Extensions of the SSM

abstract:
  We examine discrete gauge symmetries in axionic extensions of the SSM which
provide a solution of the $\mu$-problem. Automatic-PQ symmetry and proton
stability are shown to be guaranteed by certain discrete symmetries. Focusing
on the L-violating discrete symmetries we discuss two sources of neutrino
masses and their relevance for the solar neutrino problem.


title: The Large Scale Structure of the Universe: Theory {\it vs.} Observations

abstract:
  Invited talk delivered at the International Conference on General Relativity
and Cosmology (ICGC), Ahmedabad, India; 13 - 18 December 1991. To appear in its
proceedings.


title: Decay of Metastable Topological Defects

abstract:
  We systematically analyze the decay of metastable topological defects that
arise from the spontaneous breakdown of gauge or global symmetries.
Quantum-mechanical tunneling rates are estimated for a variety of decay
processes. The decay rate for a global string, vortex, domain wall, or kink is
typically suppressed compared to the decay rate for its gauged counterpart. We
also discuss the decay of global texture, and of semilocal and electroweak
strings.


title: Loop Calculations with Anomalous Gauge Boson Couplings

abstract:
  Analyses which use loop calculations to put constraints on anomalous
trilinear gauge boson couplings (TGC's) often give bounds which are much too
stringent. The reason has nothing to do with gauge invariance, in contrast to
the recent claims of de Rujula et. al., since the lagrangians used in these
calculations ARE gauge invariant, with the SU(2)L X U(1)Y symmetry nonlinearly
realized. We trace the true cause of the problem to the improper interpretation
of cutoffs in the calculation. The point is that the cutoff dependence of a
loop integral does not necessarily reflect the true dependence on the heavy
physics scale M. We illustrate that, if done carefully, one finds that the true
constraints on anomalous TGC's are much weaker.


title: Dynamical Approach to Pair Production from Strong Fields

abstract:
  Lectures Given at the Nato Advanced Study Institute-Particle Production in
Highly Excited Matter Il Ciocco, Italy July 1992 figure available on request.
Input harvmac.tex


title:
Next-to-next-to-leading order QCD analysis of the Gross-Llewellyn Smith
  sum rule and the higher twist effects

abstract:
  We present the next-to-next-to-leading order QCD analysis of the
Gross-Llewellyn Smith (GLS) sum rule in deep inelastic lepton-nucleon
scattering, taking into account dimension-two, twist-four power correction. We
discuss in detail the renormalization scheme dependence of the perturbative QCD
approximations, propose a procedure for an approximate treatment of the quark
mass threshold effects and compare the results of our analysis to the recent
experimental data of the CCFR collaboration. From this comparison we extract
the value of the strong coupling constant $\alpha_{s}^{nnl}(M_{Z},\overline{\rm
MS})= 0.115\pm0.001(stat)\pm0.005(syst)\pm0.003(twist)\pm0.0005(scheme)$. We
stress the importance of an accurate measurement of the GLS sum rule and in
particular of its $Q^{2}$ dependence.


title: From Fermion Mass Matrices to Neutrino Oscillations

abstract:
  We present an ansatz for the quark and lepton mass matrices, derivable from
SO(10) type GUTs, which accommodates a heavy $(> 92 GeV)$ top quark and permits
large mixings in the $\nu_\mu \leftrightarrow \nu_\tau$ sector (as suggested by
the recent Kamiokande and IMB data on the atmospheric neutrinos). The well
known asymptotic relations $m_b = m_\tau$, $m_s = \frac{1}{3} m_\mu$ and
$m_dm_s = m_e m_\mu$ all hold to a good approximation. Depending on $\nu_\mu
\leftrightarrow \nu_\tau$ mixing which can even be maximal, the mixing angle
relevant for solar neutrino oscillation lies in the range $7.8 \times 10^{-3}
\stackrel{_<}{_\sim} \sin^2 2\theta_{e\mu} \stackrel{_<}{_\sim} 2.1 \times
10^{-2}$. For the $^{71}$Ga experiment the event rate, normalized against the
standard solar model prediction of 132 SNU, is estimated to be between 80 and
20 SNU.


title: Predictive Neutrino Spectrum in Minimal $SO(10)$ Grand Unification

abstract:
  We show that minimal SO(10) Grand Unification models where the fermions have
Yukawa couplings to only one (complex) {\bf 10} and one {\bf 126} of Higgs
scalars lead to a very predictive neutrino spectrum. This comes about since the
standard model doublet contained in the {\bf 126} of Higgs (needed for the
see--saw mechanism) receives an induced vacuum expectation value at
tree--level, which, in addition to correcting the bad asymptotic mass relations
$m_d=m_e$ and $m_s=m_\mu$, also relates the Majorana neutrino mass matrix to
observables in the charged fermion sectors. We find that (i) the
$\nu_e-\nu_{\mu}$ mixing angle relevant for the solar neutrinos can be
considerably smaller than the Cabibbo angle and lies in the range ${\rm
sin}\theta_{e \mu}= 0-0.3$, (ii) $\nu_e-\nu_\tau$ mixing is sin$\theta_{e \tau}
\simeq 3|V_{td}| \simeq 0.05$, (iii) the $\nu_\mu-\nu_\tau$ mixing angle is
large, ${\rm sin}\theta_{\mu \tau} \simeq 3|V_{cb}|=0.12-0.16$, and (iv)
$m_{\nu_\tau}/m_{\nu_\mu} \ge 10^3$, implying that $\nu_{\mu}-\nu_\tau$
oscillations should be accessible to forthcoming experiments.


title:
A Comparison of the Use of Binary Decision Trees and Neural Networks in
  Top Quark Detection

abstract:
  The use of neural networks for signal vs.~background discrimination in
high-energy physics experiment has been investigated and has compared favorably
with the efficiency of traditional kinematic cuts. Recent work in top quark
identification produced a neural network that, for a given top quark mass,
yielded a higher signal to background ratio in Monte Carlo simulation than a
corresponding set of conventional cuts. In this article we discuss another
pattern-recognition algorithm, the binary decision tree. We have applied a
binary decision tree to top quark identification at the Tevatron and found it
to be comparable in performance to the neural network. Furthermore,
reservations about the "black box" nature of neural network discriminators do
not apply to binary decision trees; a binary decision tree may be reduced to a
set of kinematic cuts subject to conventional error analysis.


title: Vacuum Polarization and the Electric Charge of the Positron

abstract:
  We show that higher-order vacuum polarization would contribute a measureable
net charge to atoms, if the charges of electrons and positrons do not balance
precisely. We obtain the limit $|Q_e+Q_{\bar e}| < 10^{-18} e$ for the sum of
the charges of electron and positron. This also constitutes a new bound on
certain violations of PCT invariance.


title: A Quantitative Investigation of the Pomeron

abstract:
  A comparative investigation of various Pomeron models is carried out through
the study of their predicted values of $ \sigma_{tot}$, B, and
$\frac{\sigma_{el}}{\sigma_{tot}}$ in high energy pp and p$\bar{p}$ scattering.
Our results strongly support a picture of the Pomeron in which we have both
moderate blackening and expansion of the p($\bar{p}$) - p amplitude in impact
parameter space as a function of energy in the ISR-SSC domain. In particular,
we obtain an excellent reproduction of the data with a hybrid eikonal model
which combines the hard Lipatov-like QCD Pomeron with the old fashioned soft
Pomeron and Regge terms. Our analysis shows that the additive quark model, at
least in the naive form, is not compatible with the data.


title:
QCD and QED Corrections to Higgs Boson Production in Charged Current
  $ep$ Scattering

abstract:
  First order QCD and leading QED corrections to Higgs boson production in the
channel $e^-p \to \nu H^0 X; H^0 \to b\bar{b}$ are calculated for the
kinematical conditions at LEP $\otimes$ LHC ($\sqrt{s} = 1360 \GeV$) and the
interesting mass range $80 < M_H < 150 \GeV$. In the DIS scheme the QCD
corrections (not including the corrections to the branching ratio, which are
well-known) are found to be about 1\% for the total cross section and $-13\%$
to $-10\%$ for the observable cross section as defined by appropriate cuts. The
latter results depend on the definition of these cuts. The QED corrections
amount to about $-5\%$. Also obtainable with anonymous ftp from
gluon.hep.physik.uni-muenchen.de.


title:
Proton Decay and Cosmology Strongly Constrain the Minimal SU(5)
  Supergravity Model

abstract:
  We present the results of an extensive exploration of the five-dimensional
parameter space of the minimal $SU(5)$ supergravity model, including the
constraints of a long enough proton lifetime ($\tau_p>1\times10^{32}\y$) and a
small enough neutralino cosmological relic density ($\Omega_\chi h^2_0\le1$).
We find that the combined effect of these two constraints is quite severe,
although still leaving a small region of parameter space with $m_{\tilde
g,\tilde q}<1\TeV$. The allowed values of the proton lifetime extend up to
$\tau_p\approx1\times10^{33}\y$ and should be fully explored by the
SuperKamiokande experiment. The proton lifetime cut also entails the following
mass correlations and bounds: $m_h\lsim100\GeV$,
$m_\chi\approx{1\over2}m_{\chi^0_2}\approx0.15\gluino$, $m_{\chi^0_2}\approx
m_{\chi^+_1}$, and $m_\chi<85\,(115)\GeV$,
$m_{\chi^0_2,\chi^+_1}<165\,(225)\GeV$ for $\alpha_3=0.113\,(0.120)$. Finally,
the {\it combined} proton decay and cosmology constraints predict that if
$m_h\gsim75\,(80)\GeV$ then $m_{\chi^+_1}\lsim90\,(110)\GeV$ for
$\alpha_3=0.113\,(0.120)$. Thus, if this model is correct, at least one of
these particles will likely be observed at LEPII.


title: Possible Finiteness of the Higgs-Boson Mass Renormalization

abstract:
  It is shown by explicit calculation that the one-loop mass renormalization of
the Higgs boson in the standard model is gauge-independent. It could even be
rendered finite if the following mass relationships were satisfied: $m_t^2
\simeq m_H^2 = (2 M_W^2 + M_Z^2)/3$. Numerically, this would imply $m_t \simeq
84~GeV$ which is below the current experimental lower bound of 91 GeV, but
since higher-order corrections are yet to be calculated, the above hypothesis
could still have a chance of being realized.


title: Loops, Cutoffs and Anomalous Gauge Boson Couplings

abstract:
  We discuss several issues regarding analyses which use loop calculations to
put constraints on anomalous trilinear gauge boson couplings (TGC's). Many such
analyses give far too stringent bounds. This is independent of questions of
gauge invariance, contrary to the recent claims of de Rujula et. al., since the
lagrangians used in these calculations ARE gauge invariant, but the SU(2)_L X
U(1)_Y symmetry is nonlinearly realized. The real source of the problem is the
incorrect use of cutoffs -- the cutoff dependence of a loop integral does not
necessarily reflect the true dependence on the heavy physics scale M. If done
carefully, one finds that the constraints on anomalous TGC's are much weaker.
We also compare effective lagrangians in which SU(2)_L X U(1)_Y is realized
linearly and nonlinearly, and discuss the role of custodial SU(2) in each
formulation.


title:
Z', new fermions and flavor changing processes, constraints on E$_6$
  models from $\mu$ --> eee

abstract:
  We study a new class of flavor changing interactions, which can arise in
models based on extended gauge groups (rank $>$4) when new charged fermions are
present together with a new neutral gauge boson. We discuss the cases in which
the flavor changing couplings in the new neutral current coupled to the
$Z^\prime$ are theoretically expected to be large, implying that the observed
suppression of neutral flavor changing transitions must be provided by heavy
$Z^\prime$ masses together with small $Z$-$Z^\prime$ mixing angles.
Concentrating on E$_6$ models, we show how the tight experimental limit on $\mu
\rightarrow eee$ implies serious constraints on the $Z^\prime$ mass and mixing
angle. We conclude that if the value of the flavor changing parameters is
assumed to lie in a theoretically natural range, in most cases the presence of
a $Z^\prime$ much lighter than 1 TeV is unlikely.


title: Grand Unification in Non-Commutative Geometry

abstract:
  The formalism of non-commutative geometry of A. Connes is used to construct
models in particle physics. The physical space-time is taken to be a product of
a continuous four-manifold by a discrete set of points. The treatment of Connes
is modified in such a way that the basic algebra is defined over the space of
matrices, and the breaking mechanism is planted in the Dirac operator. This
mechanism is then applied to three examples. In the first example the discrete
space consists of two points, and the two algebras are taken respectively to be
those of $2\times 2$ and $1\times 1$ matrices. With the Dirac operator
containing the vacuum breaking $SU(2)\times U(1)$ to $U(1)$, the model is shown
to correspond to the standard model. In the second example the discrete space
has three points, two of the algebras are identical and consist of $5\times 5$
complex matrices, and the third algebra consists of functions. With an
appropriate Dirac operator this model is almost identical to the minimal
$SU(5)$ model of Georgi and Glashow. The third and final example is the
left-right symmetric model $SU(2)_L\times SU(2)_R\times U(1)_{B-L}.$


title: Angular Diameters as a Probe of a Cosmological Constant and $\Omega$

abstract:
  The lensing effect of curved space, which can cause the angular diameter of a
fixed reference length seen on the sky to reach a minimum and then increase
with redshift, depends sensitively on the value of the cosmological constant,
$\Lambda$, in a flat universe. The redshift of an observed minimum and the
asymptotic slope can in principle provide strong constraints on $\Lambda$. The
sensitivity to a non-zero cosmological constant in a flat universe is compared
to the sensitivity to $q_0$ in an open universe without a cosmological
constant, and to inherent ambiguities due to uncertainties in distance measures
and the possible effects of evolution. If evolutionary uncertainties can be
overcome, the reported observations of the angular diameter of compact radio
jets as a function of redshift, which appear to exhibit such a minimum, could
provide the strongest available limit on the cosmological constant in a flat
universe, and on $\Omega$ in an open universe.


title: On a Noncommutative Extension of Electrodynamics

abstract:
  The Maxwell vector potential and the Dirac spinor used to describe the
classical theory of electrodynamics both have components which are considered
to be ordinary smooth functions on space-time. We reformulate electrodynamics
by adding an additional structure to the algebra of these functions in the form
of the algebra $M_n$ of $n \times n$ complex matrices. This involves a
generalization of the notions of geometry to include the geometry of matrices.
Some rather general constraints on the reformulation are imposed which can be
motivated by considering matrix geometry in the limit of very large $n$. A few
of the properties of the resulting models are given for the values $n=2,3$. One
of the more interesting is the existence of several distinct stable phases or
vacua. The fermions can be quark-like in one and lepton-like in another.


title:
The 3d effective field theory of the high temperature abelian Higgs
  model

abstract:
  We study the 3d effective theory of the high T Abelian Higgs model with N
real scalars and gauge and scalar couplings denoted g and $\lambda$,
respectively. We find for the three cases a) $6g^2/\lambda =0(1)$, b)
$6g^2/\lambda=0(N)$ and c) $6g^2/\lambda=O(N^{2\over3})$ the following results:
a) The O(N)+O(1) potential admits only a second order phase transition, b) The
O(1) potential admits a first order transition and c) the O(N^{1\over3}) +O(1)
result gives a first order transition whose strength diminshes with N.


title: Color--Sextet Quark Condensation In QCD

abstract:
  We present the minimal sextet--quark condensation model as an attractive
alternative to the standard model. The model is constructed by a simple and
natural extension beyond the standard model and has many new interesting
features some of which can be tested readily at the existing colliders. A
crucial test may be a short--lived axion-- like $\eta_6$ of mass 30--60 GeV,
which can produce high energy photons diffractively at hadron colliders and
radiatively in $e^+ e^-$ colliders.


title:
Baryon Number Diffusion and Instabilities in the Quark/Hadron Phase
  Transition

abstract:
  Hadron bubbles that nucleate with radius $R_{nuc}$ in a quark sea (if the
phase transition is first order) are shown to be unstable to the growth of
nonspherical structure when the bubble radii exceed a critical size of $20 -
10^3$ $R_{nuc}$. This instability is driven by a very thin layer of slowly
diffusing excess baryon number that forms on the surface of the bubble wall and
limits its growth. This instability occurs on a shorter length scale than those
studied previously and these effects can thus be important for both cosmology
and heavy ion collisions.


title:
Can perturbative QCD predict a substantial part of diffractive LHC/SSC
  physics?

abstract:
  We examine a model of hadronic diffractive scattering which interpolates
between perturbative QCD and non-perturbative fits. We restrict the
perturbative QCD resummation to the large transverse momentum region, and use a
simple Regge-pole parametrization in the infrared region. This picture allows
us to account for existing data, and to estimate the size of the perturbative
contribution to future diffractive measurements. At LHC and SSC energies, we
find that a cut-off BFKL equation can lead to a measurable perturbative
component in traditionally soft processes. In particular, we show that the
total pp cross section could become as large as 228 mb (160 mb) and the rho
parameter as large as 0.23 (0.24) at the SSC (LHC).


title: Rare Kaon Decays in the $1/N_c$-Expansion

abstract:
  We study the unknown coupling constants that appear at order $p^4$ in the
Chiral Perturbation Theory analysis of $K \to \pi \gamma^* \to \pi l^+ l^-$,
$K^{+-} \to \pi^{+-} \gamma \gamma$ and $K \to \pi \pi \gamma$ decays. To that
end, we compute the chiral realization of the $\Delta S \, = \, 1$ Hamiltonian
in the framework of the $1/N_c$-expansion of the low-energy action. The
phenomenological implications are also discussed.


title:
Supersymmetric Grand Unified Theories: Two Loop Evolution of Gauge and
  Yukawa Couplings

abstract:
  We make a numerical study of gauge and Yukawa unification in supersymmetric
grand unified models and examine the quantitative implications of fermion mass
ans\"{a}tze at the grand unified scale. Integrating the renormalization group
equations with $\alpha _1(M_Z)$ and $\alpha _2(M_Z)$ as inputs, we find $\alpha
_3(M_Z)\simeq 0.111 (0.122)$ for $M_{SUSY}^{}=m_t$ and $\alpha _3(M_Z)\simeq
0.106 (0.116)$ for $M_{SUSY}^{}=1$ TeV at one-loop (two-loop) order. Including
$b$ and $\tau $ Yukawa couplings in the evolution, we find an upper limit
$m_t\ltap 200$ GeV from Yukawa unification. For given $m_t\ltap 175$ GeV, there
are two solutions for $\beta$, one with $\tan \beta > m_t/m_b$, and one with
$\sin \beta \simeq 0.78(m_t/150\;{\rm GeV})$. Taking a popular ansatz for the
mass matrices at the unified scale, we obtain a lower limit on the top quark
mass of $m_t\gtap 150 (115)$ GeV for $\alpha _3(M_Z)=0.11 (0.12)$ and an upper
limit on the supersymmetry parameter $\tan \beta \ltap 50$ if $\alpha
_3(M_Z)=0.11$. The evolution of the quark mixing matrix elements is also
evaluated.


title:
On the Finite Temperature Effective Potential in Scalar QED with N
  Flavors

abstract:
  The effective potential of scalar quantum electrodynamics with N flavors of
complex scalar fields is studied, by performing a self consistent 1/N expansion
up to next to leading order in $1/N$. Starting from the broken phase at zero
temperature, the theory exhibits a phase transition to the symmetric phase at
some finite temperature $T_c$. We work in general covariant gauges and
demonstrate the gauge invariance of both, the critical temperature $T_c$ and
the minimization condition at any finite temperature T. Furthermore, the only
minimum of the potential is at zero scalar vacuum expectation value for any
temperature $T \geq T_c$ and varies continuously to nonzero values for
temperatures below $T_c$, implying the existence of a second order phase
transition.


title: On the Anomalous Discrete Symmetry

abstract:
  We examine an interesting scenario to solve the domain wall problem recently
suggested by Preskill, Trivedi, Wilczek and Wise. The effective potential is
calculated in the presence of the QCD axial anomaly. It is shown that some
discrete symmetries such as CP and Z_2 can be anomalous due to a so-called
$K$-term induced by instantons. We point out that Z_2 domain-wall problem in
the two-doublet standard model can be resolved by two types of solutions: the
CP-conserving one and the CP-breaking one. In the first case, there exist two
Z_2-related local minima whose energy splitting is provided by the instanton
effect. In the second case, there is only one unique vacuum so that the domain
walls do not form at all. The consequences of this new source of CP violation
are discussed and shown to be well within the experimental limits in weak
interactions.


title: The Measure of Strong CP Violation

abstract:
  We investigate a controversial issue on the measure of CP violation in strong
in teractions. In the presence of nontrivial topological gauge configurations,
the $\theta$-term in QCD has a profound effect: it breaks the CP symmetry. The
CP-violating amplitude is shown to be determined by the vacuum tunneling
process, where the semiclassical method makes most sense. We discuss a
long-standing dispute on whether the instanton dynamics satisfies or not the
anomalous Ward identity (AWI). The strong CP violation measure, when complying
with the vacuum alignment, is proportional to the topological susceptibility.
We obtain an effective CP-violating lagrangian different from that provided by
Baluni. To solve the IR divergence problem of the instanton computation, We
present a ``classically gauged'' Georgi-Manohar model and derive an effective
potential which uniquely determines an explicit $U(1)_A$ symmetry breaking
sector. The CP violation effects are analyzed in this model. It is shown that
the strong CP problem and the $U(1)$ problem are closely related. Some possible
solutions to both problems are also discussed with new insights.


title: Cosmic Neutrinos from Unstable Relic Particles

abstract:
  We derive constraints on the relic abundance of a generic particle of mass
$\sim~1-10^{14}$ TeV which decays into neutrinos at cosmological epochs, using
data from the Fr\'ejus and IMB nucleon decay detectors and the Fly's Eye air
shower array. The lifetime of such unstable particles which may constitute the
dark matter today is bounded to be greater than $\sim~10^{14}-10^{18}$ yr,
depending on the mass. For lifetimes shorter than the age of the universe,
neutrino energy losses due to scattering and the expansion redshift become
important and set limits to the ability of neutrino observatories to probe the
early universe.


title: Anomalous Gauge-Boson Couplings at Hadron Supercolliders

abstract:
  We discuss anomalous gauge boson couplings at hadron supercolliders. We
review the usual description of these couplings, as well as the studies of a
strongly interacting electroweak symmetry breaking sector. We present an
effective field theory formulation of the problem that relates the two
subjects, and that allows a consistent and systematic analysis. We end with
some phenomenology.


title: Primordial magnetic fields from pseudo-Goldstone bosons

abstract:
  The existence of large-scale magnetic fields in galaxies is well established,
but there is no accepted mechanism for generating a primordial field which
could grow into what is observed today. We discuss a model which attempts to
account for the necessary primordial field by invoking a pseudo-Goldstone boson
coupled to electromagnetism. The evolution of this boson during inflation
generates a magnetic field; however, it seems difficult on rather general
grounds to obtain fields of sufficient strength on astrophysically interesting
scales.


title: Electromagnetic Interactions in Heavy Hadron Chiral Theory

abstract:
  Electromagnetic interactions are incorporated into Heavy Hadron Chiral
Perturbation Theory. Short and long distance magnetic moment contributions to
the chiral Lagrangian are identified, and $M1$ radiative decays of heavy vector
mesons and sextet baryons are studied. Using recent CLEO $D^*$ branching
fraction ratio data, we fit the meson coupling to the axial vector Goldstone
current and find $g_1^2 = 0.34 \pm 0.48$ for $\mc = 1700 \MeV$. Finally, we
obtain model independent predictions for total and partial widths of charm and
bottom vector mesons.


title: Summing One-Loop Graphs at Multi-Particle Threshold

abstract:
  It is shown that the technique recently suggested by Lowell Brown for summing
the tree graphs at threshold can be extended to calculate the loop effects.
Explicit result is derived for the sum of one-loop graphs for the amplitude of
threshold production of $n$ on-mass-shell particles by one virtual in the
unbroken $\lambda \phi^4$ theory. It is also found that the tree-level
amplitude of production of $n$ particles by two incoming on-mass-shell
particles vanishes at the threshold for $n > 4$.


title: Radiative $D^*$ Decay Using Heavy Quark and Chiral Symmetry

abstract:
  The implications of chiral $SU(3)_L \times SU(3)_R$ symmetry and heavy quark
symmetry for the radiative decays $D^{*0}\to D^0\gamma$, $D^{*+}\to D^+\gamma$,
and $D_s^*\to D_s\gamma$ are discussed. Particular attention is paid to $SU(3)$
violating contributions of order $m_q^{1/2}$. Experimental data on these
radiative decays provide constraints on the $D^* D\pi$ coupling.


title: Meson Mass Splittings in the Nonrelativistic Model

abstract:
  Mass splittings between isodoublet meson pairs and between $0^{-}$ and
$1^{-}$ mesons of the same valence quark content are computed in a detailed
nonrelativistic model. The field theoretic expressions for such splittings are
shown to reduce to kinematic and Breit-Fermi terms in the nonrelativistic
limit. Algebraic results thus obtained are applied to the specific case of the
linear-plus-Coulomb potential, with resultant numbers compared to experiment.


title: The $\mu$ Problem and the Invisible Axion

abstract:
  The $\mu$ term in the supersymmetric standard model is known to" be nonzero.
Supersymmetry breaking at the intermediate scale may provide the needed $\mu$
term and the invisible axion. A possible solution of this $\mu$ problem in
superstring models is also discussed.


title: Physics from Vacuum Alignment in A Technicolor Model

abstract:
  I describe a technicolor model (without walking) of all interactions up to
energies of the order of 1000~TeV. The low energy extended technicolor model
has the CTSM form. But at intermediate energy scales, additional interactions
are required to give the KM mixing. I discuss the characteristic flavor
changing neutral current interactions arising from this flavor physics below
1000~TeV.


title: Supersymmtric Baryogenesis

abstract:
  Requiring that the baryon number of the universe be generated by anomalous
electroweak interactions places strong constraints on the minimal
supersymmetric standard model. In particular, the electric dipole moment of the
neutron must be greater than $10^{-27}$e-cm. Improvement of the current
experimental bound on the neutron's electric dipole moment by one order of
magnitude would constrain the lightest chargino to be lighter than 88 GeV, and
the the lightest neutralino to be lighter than 44 GeV. In extensions of this
model with gauge singlet superfields all of these bounds are eliminated.


title:
Vortex Production in a First Order Phase-Transition at Finite
  Temperature

abstract:
  We simulate the production of vortices in a first order phase transition at
finite temperature. The transition is carried out by randomly nucleating
critical bubbles and the effects of thermal fluctuations (which could be
relevant for vortex production) are represented by randomly nucleating
subcritical bubbles. Our results show that the presence of subcritical bubbles
suppresses vortices with clear and prominent profiles, though net number of
vortices is consistent with theoretical estimates. We also determine the
typical speed of vortices arising due to randomness associated with the phase
transition to be about 0.5.


title: Estimates with an Effective Chiral Lagrangian for Heavy Mesons

abstract:
  On the basis of an effective lagrangian incorporating approximate chiral
symmetry and heavy-quark spin and flavor symmetries, and by use of information
on leptonic decays, we estimate the effective $D^\star D\pi$ coupling.


title:
Light Vector Resonances in the Effective Chiral Lagrangian for Heavy
  Mesons

abstract:
  We modify a chiral effective lagrangian recently suggested to describe
interactions of the light pseudoscalars with mesons containing a heavy quark,
so as to incorporate light vector resonances, such as $\rho$, etc. The
modification uses the hidden gauge symmetry approach. As a preliminary example
we present an application to the semileptonic $D\to K^\star$ decay.


title: Exclusive Rare Decay $B\rightarrow K^{\ast}\gamma$

abstract:
  We show that the exclusive decay $B\rightarrow K^{\ast}\gamma$ can be related
to the semileptonic decay $B\rightarrow\rho e\bar{\nu}$ using heavy-quark
symmetry and $SU(3)$ flavor symmetry. A direct measurement of the
$q^{2}$-spectrum for the semileptonic decay can provide relevant information
for the exclusive rare decay.


title: Precise predictions for mt, Vcb and tan

abstract:
  The fermion mass and mixing angle predictions of a recently proposed
framework are investigated for large b and $\tau$ Yukawa couplings. A new
allowed region of parameters is found for this large $\tan \beta$ case. The two
predictions which are substantially altered, $m_t$ and $\tan \beta$, are
displayed, including the dependence on the inputs $|V_{cb}|$, $m_c$, $m_b$ and
$\alpha_s$. A simple restriction on this framework yields an additional
prediction, for $|V_{cb}|$. If the b,t, and $\tau$ Yukawas are equal at the GUT
scale then $|\Vcb|$ is predicted and the top quark mass is constrained to lie
in the range $\mt = 179. \pm 4.$ GeV.


title: Tau Signals of R-parity breaking at LEP 200

abstract:
  The detectability at LEP 200 of explicit $R$-parity breaking by tau-number
$(L_\tau)$ violating operators is considered. The assumption of
$L_\tau$-violation is motivated by the relative lack of constraints on such
couplings but similar considerations apply to explicit $L_e$- or
$L_\mu$-violation. The $LSP$, now unstable, and not necessarily neutral, decays
via $L_\tau$-violating modes. Only signals from the production and decays of
$LSP$ pairs are considered, thereby avoiding any dependence on the sparticle
mass spectrum. Rather spectacular signals are predicted: spherical events with
$m$ leptons (usually containing at least one $\tau$) and $n$ jets $(m,n \leq
4)$, the most characteristic of which are like-sign $\tau\tau$ events. These
signals are enumerated for each $LSP$ candidate and quantitative estimates are
provided for the favoured case when the $LSP$ is a neutralino. Other new
physics signals, which can mimic these signatures, are also briefly discussed.


title:
A New Time Contour for Equilibrium Real-Time Thermal Field Theories (7
  characters altered for email)

abstract:
  A new time contour is used to derive real-time thermal field theory. Unlike
previous path integral approaches, no contributions to the generating
functional are dropped.


title:
Thermal Bosonic Green Functions Near Zero Energy (6 characters removed
  for email)

abstract:
  The properties of the various types of bosonic Green functions at finite
temperature in the zero energy limit are considered in the light of recent
work.


title: Can a strongly interacting Higgs boson rescue SU(5)?

abstract:
  Renormalization group analyses show that the three running gauge coupling
constants of the Standard Model do not become equal at any energy scale. These
analyses have not included any effects of the Higgs boson's self-interaction.
In this paper, I examine whether these effects can modify this conclusion.


title: Technicolor Theories with Negative S

abstract:
  We show that the pseudo Nambu--Goldstone boson contribution to the
Peskin--Takeuchi electroweak parameter $S$ can be negative in a class of
technicolor theories. This negative contribution can be large enough to cancel
the positive techni-hadron contribution, showing that electroweak precision
tests alone cannot be used to rule out technicolor as the mechanism of
electroweak symmetry breaking.


title: Role of Light Vector Mesons in the Heavy Particle Chiral Lagrangian

abstract:
  We give the general framework for adding "light" vector particles to the
heavy hadron effective chiral Lagrangian. This has strong motivations both from
the phenomenological and aesthetic standpoints. An application to the already
observed $D \rightarrow \overbar{K^*} $ weak transition amplitude is discussed.


title: Three-Body Interactions Among Nucleons and Pions

abstract:
  A chiral invariant effective Lagrangian may be used to calculate the
three-body interactions among low-energy pions and nucleons in terms of known
parameters. This method is illustrated by the calculation of the pion-nucleus
scattering length.


title: Collapsing Sub-Critical Bubbles

abstract:
  In the standard scenario, the electroweak phase transition is a first order
phase transition which completes by the nucleation of critical bubbles.
Recently, there has been speculation that the standard picture of the
electroweak phase transition is incorrect. Instead, it has been proposed that
throughout the phase transition appreciable amounts of both broken and unbroken
phases of $SU(2)$ coexist in equilibrium. I argue that this can not be the
case. General principles insure that the universe will remain in a homogenous
state of unbroken $SU(2)$ until the onset of critical bubble production.


title: Electric Charge Quantization

abstract:
  Experimentally it has been known for a long time that the electric charges of
the observed particles appear to be quantized. An approach to understanding
electric charge quantization that can be used for gauge theories with explicit
$U(1)$ factors -- such as the standard model and its variants -- is
pedagogically reviewed and discussed in this article. This approach uses the
allowed invariances of the Lagrangian and their associated anomaly cancellation
equations. We demonstrate that charge may be de-quantized in the
three-generation standard model with massless neutrinos, because differences in
family-lepton--numbers are anomaly-free. We also review the relevant
experimental limits. Our approach to charge quantization suggests that the
minimal standard model should be extended so that family-lepton--number
differences are explicitly broken. We briefly discuss some candidate extensions
(e.g. the minimal standard model augmented by Majorana right-handed neutrinos).


title:
CP Violating Form Factors for Three Gauge Boson Vertex in the Two Higgs
  Doublet and Left-Right symmetric Models

abstract:
  In this paper we calculate the one loop contributions to the CP violating
three gauge boson couplings in two-Higgs doublet and Left--Right symmetric
models. In the two-Higgs doublet model only a P conserving and CP violating
coupling is generated, and it can be large as $10^{-3}$. In the Left--Right
symmetric model both P conserving and violating couplings are generated. Due to
constraints on the $W_L$--$W_R$ mixing, these couplings are small.


title: Radiative Semileptonic Kaon Decays

abstract:
  We evaluate the matrix elements for the radiative kaon decays $K^+ \to
l^+\nu_l\gamma$, $l^+ \nu_l l'^+ l'^-$ and $K \to \pi l \nu_l\gamma$ \ ($l,\ l'
= e,\mu$) to next-to-leading order in chiral perturbation theory. We calculate
total rates and rates with several kinematical cuts and confront the results
with existing data. Measurements at future kaon facilities will allow for a
more detailed comparison between theory and experiment.


title: Chiral Lagrangians for Radiative Decays of Heavy Hadrons

abstract:
  The radiative decays of heavy mesons and heavy baryons are studied in a
formalism which incorporates both the heavy quark symmetry and the chiral
symmetry. The chiral Lagrangians for the electromagnetic interactions of heavy
hadrons consist of two pieces: one from gauging electromagnetically the
strong-interaction chiral Lagrangian, and the other from the anomalous magnetic
moment interactions of the heavy baryons and mesons. Due to the heavy quark
spin symmetry, the latter contains only one independent coupling constant in
the meson sector and two in the baryon sector. These coupling constants only
depend on the light quarks and can be calculated in the nonrelativistic quark
model. However, the charm quark is not heavy enough and the contribution from
its magnetic moment must be included. Applications to the radiative decays
$D^\ast \rightarrow D \gamma~,~B^\ast \rightarrow B \gamma~,~ \Xi^\prime_c
\rightarrow \Xi_c \gamma~, \Sigma_c \rightarrow \Lambda_c \gamma$ and $\Sigma_c
\rightarrow \Lambda_c \pi \gamma$ are given. Together with our previous results
on the strong decay rates of $D^\ast \rightarrow D \pi$ and $\Sigma_c
\rightarrow \Lambda_c \pi$, predictions are obtained for the total widths and
branching ratios of $D^\ast$ and $\Sigma_c$. The decays $\Sigma^+_c \rightarrow
\Lambda^+_c \pi^0 \gamma $ and $\Sigma^0_c \rightarrow \Lambda^+_c \pi^- \gamma
$ are discussed to illustrate the important roles played by both the heavy
quark symmetry and the chiral symmetry.


title: Heavy Quark Symmetry Violation in Semileptonic Decays of D Mesons

abstract:
  The decays of $D$ mesons to $K l \nu$ and $K^* l \nu$ final states exhibit
significant deviations from the predictions of heavy-quark symmetry, as one
might expect since the strange quark's mass is of the same order as the QCD
scale. Nonetheless, in order to understand where the most significant effects
might lie for heavier systems (such as $B \to D l\nu$ and $B \to D^* l\nu$),
the pattern of these deviations is analyzed from the standpoint of perturbative
QCD and ${\cal O}(1/m_s)$ corrections. Two main effects are noted. First, the
perturbative QCD corrections lead to an overall decrease of predicted rates,
which can be understood in terms of production of excited kaonic states.
Second, ${\cal O}(1/m_s)$ effects tend to cancel the perturbative QCD
corrections in the case of $Kl\nu$ decay, while they have minimal effect in
$K^*l\nu$ decay.


title:
Exclusive heavy meson pair production by $\gamma\gamma$ collision in
  heavy quark effective theory

abstract:
  The spin and flavor symmetries of the heavy quark effective theory are
employed to discuss the exclusive cross sections for pair production of heavy
mesons in photon-photon collision. The ratios of the exclusive cross sections
for heavy mesons are obtained explicitly and the validity of results is
discussed.


title: The 3-graviton vertex function in thermal quantum gravity

abstract:
  The high temperature limit of the 3-graviton vertex function is studied in
thermal quantum gravity, to one loop order. The leading ($T^4$) contributions
arising from internal gravitons are calculated and shown to be twice the ones
associated with internal scalar particles, in correspondence with the two
helicity states of the graviton. The gauge invariance of this result follows in
consequence of the Ward and Weyl identities obeyed by the thermal loops, which
are verified explicitly.


title:
Nrqed in Bound States: Applying Renormalization to an Effective Field
  Theory

abstract:
  This is a pedagogical introduction to NRQED, a low enery approximation of QED
which can be made to reproduce QED to an arbitrary precision. It is especially
useful when applied to nonrelativistic bound states. We start by explaining why
QED is so difficult to apply to nr bound states, why NRQED makes it much
simpler and then proceed to do an explicit calculation. We also briefly discuss
what this can teach us about ``new'' physics beyond QED. This is based on a
talk given at the XIV MRST meeting in Toronto.


title: CP violation in top pair production at an e^+e^- collider

abstract:
  We investigate a possible CP violating effect in $e^+e^-$ annihilation into
$t\bar t$ top quark pairs. As an illustrative example, we assume the source of
the CP nonconservation is in the Yukawa couplings of a neutral Higgs boson
which contain both scalar and pseudoscalar pieces. One of the interesting
observable effects is the difference in production rates between the two CP
conjugate polarized $t\bar t$ states.


title:
Second Order Power Corrections in the Heavy Quark Effective Theory I.
  Formalism and Meson Form Factors

abstract:
  In the heavy quark effective theory, hadronic matrix elements of currents
between two hadrons containing a heavy quark are expanded in inverse powers of
the heavy quark masses, with coefficients that are functions of the kinematic
variable $v\cdot v'$. For the ground state pseudoscalar and vector mesons, this
expansion is constructed at order $1/m_Q^2$. A minimal set of universal form
factors is defined in terms of matrix elements of higher dimension operators in
the effective theory. The zero recoil normalization conditions following from
vector current conservation are derived. Several phenomenological applications
of the general results are discussed in detail. It is argued that at zero
recoil the semileptonic decay rates for $B\to D\,\ell\,\nu$ and $B\to
D^*\ell\,\nu$ receive only small second order corrections, which are unlikely
to exceed the level of a few percent. This supports the usefulness of the heavy
quark expansion for a reliable determination of $V_{cb}$.


title:
Second Order Power Corrections in the Heavy Quark Effective Theory II.
  Baryon Form Factors

abstract:
  The analysis of $1/m_Q^2$ corrections of the previous paper is extended to
the semileptonic decays of heavy baryons. We focus on the simplest case, the
ground state $\Lambda_Q$ baryons, in which the light degrees of freedom are in
a state of zero total angular momentum. The formalism, while identical in
spirit, is considerably less cumbersome than for heavy mesons. The general
results are applied to the semileptonic decay
$\Lambda_b\to\Lambda_c\,\ell\,\nu$. An estimate of the leading power
corrections to the decay rate at zero recoil, which are of order $1/m_Q^2$, is
presented. It is pointed out that a measurement of certain asymmetry parameters
would provide a direct measurement of $1/m_Q^2$ corrections. Finally, it is
shown how the analysis could be extended to include excited heavy baryons such
as the $\Sigma_Q$ and the $\Sigma_Q^*$.


title: Comment on "Summing One-Loop Graphs at Multi-Particle Threshold"

abstract:
  The propagator of a virtual $\phi$-field with emission of $n$ on-mass-shell
particles all being exactly at rest is calculated at the tree-level in $\lambda
\phi^4$ theory by directly solving recursion equations for the sum of Feynman
graphs. It is shown that the generating function for these propagators is
equivalent to a Fourier transform of the recently found Green's function within
the background-field technique for summing graphs at threshold suggested by
Lowell Brown. Also the derivation of the result that the tree-level
on-mass-shell scattering amplitudes of the processes $2 \to n$ are exactly
vanishing at threshold for $n > 4$ is thus given in the more conventional
Feynman diagram technique.


title:
QCD Sum Rule Analysis of the Subleading Isgur-Wise Form Factor
  $\chi_2(v\cdot v')$

abstract:
  We present a QCD sum rule calculation of the spin-symmetry violating
universal function $\chi_2(v\cdot v')$, which appears at order $1/m_Q$ in the
heavy quark expansion of meson form factors. This function vanishes in the
standard approximation, where radiative effects are neglected. For the first
time, the complete set of diagrams arising at order $\alpha_s$ is evaluated. In
particular, we find $\chi_2(1) = -(3.8\pm 0.4)\%$ at zero recoil, indicating
that $1/m_Q$ corrections induced by the chromo-magnetic moment operator are
small.


title: Chiral effective action with heavy quark symmetry

abstract:
  We derive an effective action combining chiral and heavy quark symmetry,
using approximate bosonization techniques of QCD. We explicitly show that the
heavy-quark limit is compatible with the large $N_c$ (number of color) limit in
the meson sector, and derive specific couplings between the light and heavy
mesons ($D$, $D^*$, ...) and their chiral partners. The relevance of this
effective action to solitons with heavy quarks describing heavy baryons is
discussed.


title: Feynman Parametrization and the Degenerate Electron Gas

abstract:
  We give an alternate derivation of Weldon's formula for combining products of
factors with non identical analytic behavior. While such a formula would appear
to be useful in finite temperature calculations, we give an example of a zero
temperature calculation, namely, the degenerate electron gas, to justify the
result.


title:
Note on Tests of the Factorization Hypothesis and the Determination of
  Meson Decay Constants

abstract:
  We discuss various tests of the factorization hypothesis making use of the
close relationship between semi-leptonic and factorized nonleptonic decay
amplitudes. It is pointed out that factorization leads to truely
model-independent predictions for the ratio of nonleptonic to semi-leptonic
decay rates, if in the nonleptonic decay a spin one meson of arbitrary mass or
a pion take the place of the lepton pair. Where the decay constants of those
mesons are known, these predictions represent ideal tests of the factorization
hypothesis. In other cases they may be used to extract the decay constants.
Currently available data on the decays $\bar B^0 \to D^+\pi^-,\, D^{*+}\pi^-,\,
D^+\varrho^-,\, D^{*+}\varrho^-$ are shown to be in excellent agreement with
the factorization results. A weighted average of the four independent values
for the QCD coefficient $a_1$ extracted from the data gives $a_1=1.15\pm 0.06$
suggesting that it may be equal to the Wilson coefficient $c_1(\mu)$ evaluated
at the scale $\mu = m_b$.


title: Soliton Structure of Heavy Baryons

abstract:
  Heavy-quark baryons are described as a bound heavy-meson-soliton system in a
Lagrangian that combines chiral symmetry and heavy-quark symmetry. We introduce
a ``Wess-Zumino type" term and show that it dominates the binding of a heavy
meson to a soliton. The connection between this model and the Callan-Klebanov
model is established to $O(N_c^{-1} \cdot m_\Phi^0)$ where $m_\Phi$ is the mass
of the heavy-meson (isospin) doublet $\Phi$ or $\Phi^*$.


title: Non-Abelian Boltzmann Equation for Mixing and Decoherence

abstract:
  We consider particle oscillations and their damping in second-quantized form.
We find that the damping or "decoherence" may be described by a Boltzmann-like
collision integral with "non-abelian blocking factors" (fermions). Earlier
results are generalized in that the momentum degrees of freedom are included
and that the mixing equations become intrinsically non-linear at high
densities.


title:
The Isgur-Wise Function to $O(\alpha_s)$ from Sum Rules in the Heavy
  Quark Effective Theory

abstract:
  Radiative corrections to both perturbative and non-perturbative contributions
are added to existing calculations of the Isgur-Wise function $\xi_{IW}$. To
this end, we develop a method for calculating two-loop integrals in the heavy
quark effective theory involving two different scales. The inclusion of
$O(\alpha_s)$ terms causes $\xi_{IW}$ to decrease as compared to the lowest
order result and shows the importance of quantum effects. The slope parameter
$\rho^2$ violates the bound given by de Rafael and Taron.


title: On Testing V-A in Lambda_b Decays

abstract:
  We comment on a recent suggestion by Amundson, Rosner, Worah and Wise to test
the chirality of the $b$-quark decay coupling via polarized $\Lambda_b$ baryons
produced in $e^+e^-\rightarrow Z\rightarrow \Lambda_b +X$. We study the effect
of contributions from an amplitude in which a right-handed $b$ to $c$ current
couples to a V-A lepton current.


title: Large Penguin effects in the CP Asymmetry of B0d ->pi+pi-

abstract:
  Penguin effects in the CP asymmetries of $B^0_d\rightarrow \pi^+\pi^-$ ,
$\bd\rightarrow\rho^{\pm}\pi^{\mp}$ and $\bd\rightarrow a^{\pm}_1 \pi^{\mp}$
are studied as function of the CKM unitarity triangle $\alpha$. Despite a
fairly small penguin amplitude, it leads to quite sizable uncertainties in the
determination of $\sin(2\alpha)$ from all but very large asymmetries. This
effect is maximal for vanishing final state interaction phases, for which it
can cause, for instance, an asymmetry of 40\%\ if $\alpha=\pi/2$.


title: Stable diquark matter ?

abstract:
  Two-quark correlations ({\it diquarks}) may play an important role in
hadronic physics, particularly near the deconfinement point. This opens the
possibility of a net energy gain by means of a (non-perturbative) quark pairing
effect, perheps up to stabilize diquark droplets. We address in this work the
possibility of a self-bound, stable state of bulk diquark matter.


title:
Numerical Study of the Lowest Energy Configurations for Global
  String-Antistring Pairs

abstract:
  We investigate the lowest energy configurations for string - antistring pairs
at fixed separations by numerically minimizing the energy. We show that for
separations smaller than a critical value, a region of false vacuum develops in
the middle due to large gradient energy density. Consequently, well defined
string - antistring pairs do not exist for such separations. We present an
example of vortex - antivortex production by vacuum bubbles where this effect
seems to play a dynamical role in the annihilation of the pair. We also study
the dependence of the energy of an string-antistring pair on their separation
and find deviations from a simple logarithmic dependence for small separations.


title: Temperature Renormalization Group and Resummation

abstract:
  The temperature renormalization group equation (TRGE) is compared with a
diagrammatic expansion for the $(\phi^4)_4$-theory. It is found that the
one-loop TRGE resums the leading powers of temperature for the effective mass.
A two-loop contribution to TRGE is required to do the leading resummation for
the coupling constant. It is also shown that the higher order TRGE resums
subleading powers of temperature.


title: Quantum Corrections to Deep Bags

abstract:
  Nontopological solitons, or ``bags,'' can arise when fermions acquire their
mass through a Yukawa coupling to some scalar field. Bags have played an
important role in models of baryons, nuclei, and more recently, in the idea
that a Higgs condensate may form around a very heavy top quark. It has been
claimed that deep bags, which correspond to tightly-bound states of fermions,
will form when the Yukawa coupling is strong. Quantum corrections, however, are
significant in this regime. We examine the effects of these quantum corrections
on the formation of nontopological solitons in an exactly solvable large-$N$
model. We find that quantum bags differ dramatically from those of the
classical theory. In particular, for large Yukawa coupling, the bags remain
shallow and the fermions weakly bound.


title:
Neutron electric dipole moment due to Higgs exchange in Left-Right
  symmetric models

abstract:
  In this paper we study the neutron electric dipole moment (EDM) due to Higgs
boson exchange in Left-Right symmetric models. In pseudo-manifest Left-Right
symmetric models, the neutral Higgs contribution is smaller than that from the
charged Higgs. The charged Higgs contribution at the two loop level can be as
large as the experimental upper bound. In non (pseudo) manifest Left-Right
symmteric models, the neutral Higgs exchange contribution can reach the
experimental upper bound. The Higgs exchange contributions can be more
important than the ones from W-boson exchange due to $W_L - W_R$ mixing.


title: Planck Scale Effects on the Majoron

abstract:
  The hypothesis that non-perturbative gravitational effects lead to explicit
breaking of global symmetries is considered in the context of Majoron models.
We find that the nonvanishing Majoron mass generated by these effects can
overclose the universe unless the massive Majoron is unstable. The cosmological
mass density constraints can then be satisfied only if $V_{BL} < 10$ TeV, where
$V_{BL}$ is the scale of $B-L$ symmetry breaking.


title: Radiative corrections in processes at the SSC

abstract:
  We discuss radiative corrections for interactions in the SSC environment.
Based on the theory of Yennie, Frautschi and Suura, we develop appropriate
Monte Carlo event generators to compute the background electromagnetic
radiation. Our results indicate that multiple-photon effects must be taken into
account in the study of SSC physics such as Higgs decay.


title: Summing one-loop graphs in a theory with broken symmetry

abstract:
  The method suggested by Lowell Brown for calculating multi-particle threshold
amplitudes is extended to the one-loop level in scalar theories with broken
reflection symmetry. A result for the threshold amplitude for multiparticle
production is derived. It is also shown that the tree-level amplitude for 2
on-mass-shell particles producing $n$ particles vanishes at the kinematical
threshold for $n>2$


title:
Discrete quark-lepton symmetry need not pose a cosmological domain wall
  problem

abstract:
  Quarks and leptons may be related to each other through a spontaneously
broken discrete symmetry. Models with acceptable and interesting collider
phenomenology have been constructed which incorporate this idea. However, the
standard Hot Big Bang model of cosmology is generally considered to eschew
spontaneously broken discrete symmetries because they often lead to the
formation of unacceptably massive domain walls. We point out that there are a
number of plausible quark-lepton symmetric models which do not produce
cosmologically troublesome domain walls. We also raise what we think are some
interesting questions concerning anomalous discrete symmetries.


title: The Rule of Discarding $1/N_c$ in Inclusive Weak Decays. II

abstract:
  We calculate the leading preasymptotic correction to the inclusive width
$b\rightarrow \bar c c s$ (two massive quarks in the final state) due to the
operator $\vec \sigma \vec H$. It is found that this correction tends to cancel
the $1/N_c$ part of the inclusive width calculated using naive factorization.
The absolute value of the effect is of order 0.25. We also discuss how
quark-hadron duality is realized in the inclusive decays.


title: The Extended Bess Model: Bounds from Precision Electroweak Measurements

abstract:
  We present an effective Lagrangian parameterization describing scalar,
vector, and axial-vector bound states, originating from a strong breaking of
the electroweak symmetry, based on the global symmetry $SU(N)_L\otimes
SU(N)_R$. In this approach vector and axial-vector bound states are gauge
bosons associated to a hidden $SU(N)_L\otimes SU(N)_R$ symmetry. After the
gauging of the electroweak symmetry, the corrections to the self-energies of
the standard model gauge bosons are calculated and bounds on the parameter
space of the model arising from precision measurements are studied. The
self-energy corrections arise from spin 1 mixings, pseudogoldstones loops,
pseudogoldstone-spin 1 loops, and tadpole terms. The one-loop terms tend to
decrease both isospin conserving and isospin violating corrections. Careful
calculation for standard $SU(8)$ QCD-scaled technicolor shows that strictly
this model (which has however serious theoretical difficulties on his own) is
still marginally allowed at present experimental precision.


title: $D$-$\bar D$ Mixing in Heavy Quark Effective Field Theory

abstract:
  I analyze $D$-$\ol D$ mixing using the techniques of heavy quark effect field
theory. The analysis suggests that the there may be important cancellations
among the dispersive effects of different kinds of final states, so that the
total mixing may be considerably smaller than previous estimates.


title: Neutralino Dark Matter in a Class of Unified Theories

abstract:
  The cosmological significance of the neutralino sector is studied for a class
of models in which electroweak symmetry breaking is seeded by a gauge singlet.
Extensive use is made of the renormalisation group equations to significantly
reduce the parameter space, by deriving analytic expressions for all the
supersymmetry-breaking couplings in terms of the universal gaugino mass
$m_{1/2}$, the universal scalar mass $m_0$ and the coupling $A$. The
composition of the LSP is determined exactly below the W mass, no
approximations are made for sfermion masses, and all particle exchanges are
considered in calculating the annihilation cross-section; the relic abundance
is then obtained by an analytic approximation. We find that in these models,
stable neutralinos may make a significant contribution to the dark matter in
the universe.


title: The Vector Equivalence Technique

abstract:
  We present the Vector Equivalence technique. This technique allows a simple
and systematic calculating of Feynman diagrams involving massive fermions at
the matrix element level. As its name suggests, the technique allows two
Lorentz four-vectors to serve as an equivalent of two external fermions. In
further calculations, traces involving these vectors replace the matrix element
with the external fermions. The technique can be conveniently used for both
symbolic and numeric calculations.


title: Particle Width Effect on $CP$-Violating Asymmetries

abstract:
  $CP$-violating asymmetries calculated from the Breit-Wigner approximation for
unstable particle propagators violate $CPT$. A formalism satisfying $CP$
invariance and unitarity is presented. Applications are given to $t$ decays.
For the decay $t\to b\nu_{\tau}\bar{\tau}$ in a class of $CP$-violating models
the $CP$-violating asymmetry turns out to be $10^{-4}$ times smaller than the
previously reported results.


title: Spontaneous CP Violation, Small Instanton and Invisible Axion

abstract:
  I propose a variant invisible axion model of spontaneous CP violation at the
electroweak scale without CP domain wall and `strong CP' problems. Both large
size QCD and small size non-QCD instantons break CP and Peccei-Quinn
symmetries, and render cosmologically harmful CP domain walls unstable. The
decaying epoch depends on size of small instanton effects, and is around 100 eV
if the current neutron electric dipole moment bound is maximally saturated. The
model satisfies constraints from primordial D and He photo-dissociation and
black hole formation, while producing cosmologically interesting size of
gravitational waves and galaxy-scale density perturbations.


title: The Supersymmetric Singlet Majoron

abstract:
  We study the supersymmetrized version of the singlet majoron model and,
performing an analysis of the renormalization group equation improved
potential, we find that a spontaneous breaking of $R$-parity can be achieved
for a wide range of the parameters. Studying the finite temperature effective
potential, we show that the phase transition leading to $R$-parity breaking can
be of the first order and can occur at temperatures below the weak scale, thus
avoiding any constraint coming from the requirement of the preservation of the
baryon asymmetry in the early Universe.


title: Model Dependence of Baryon Decay Enhancement by Cosmic Strings

abstract:
  Cosmic strings arising from GUTs can catalyse baryon decay processes with
strong interaction cross sections. We examine the mechanism by which the cross
section is enhanced and find that it depends strongly on the details of the
distribution of gauge fields within the string core. We propose a calculational
scheme for estimating wavefunction amplification factors and also a physical
understanding of the nature of the enhancement process.


title: Limits on Neutrino Radiative Decay from Sn1987a

abstract:
  We calculate limits on the properties of neutrinos using data from gamma-ray
detectors on the Pioneer Venus Orbiter and Solar Max Mission satellites. A
massive neutrino decaying in flight from the supernova would produce gamma rays
detectable by these instruments. The lack of such a signal allows us to
constrain the mass, radiative lifetime, and branching ratio to photons of a
massive neutrino species produced in the supernova. Presented at Beyond The
Standard Model III, June, 1992.


title: Majorons Without Majorana Masses and Neutrinoless Double Beta Decay

abstract:
  We explain excess events near the endpoints of the double beta decay spectra
of several elements, using the neutrinoless emission of massless Goldstone
bosons. Models with scalars carrying lepton number $-2$ are proposed for this
purpose so that ordinary neutrinoless double beta decay is forbidden, and we
can raise the scale of global symmetry breaking above the 10 keV scale needed
for observable emission of conventional Majorons in double beta decay. The
electron spectrum has a different shape, and the rate depends on different
nuclear matrix elements, than for the emission of ordinary Majorons.


title:
Stringy Origin of Neutrino Masses within the Minimal Supersymmetric
  Standard Model

abstract:
  We present a ``gravity-induced'' seesaw mechanism, which accommodates
neutrino masses ($m_\nu\propto m_u^2/M_I$, with $m_u$ the corresponding quark
mass and $M_I\simeq 4\times10^{11}$ GeV) compatible with the MSW study of the
Solar neutrino deficit within the minimal supersymmetric Standard Model (the
grand desert with the gauge coupling unification at $M_U\simeq 2\times10^{16}$
GeV). We show that for large radius ($R^2/\alpha '={\cal O}(20)$) Calabi-Yau
spaces, threshold corrections ensure $M_U^2=M_C^2/{\cal O} (2R^2/\alpha')$ and
the magnitude of the non-renormalizable terms in the superpotential yields
$M_I= {\cal O}(e^{-R^2/\alpha'})M_C$. Here $M_C=g\times 5.2\times 10^{17}$GeV
is the scale of the tree level (genus zero) gauge coupling ($g$) unification.


title: Double Beta Decay

abstract:
  I review the subject of double beta decay with emphasis upon its implications
for the neutrino. It is shown that even if right-handed currents provide the
phenomenological mechanism for no-neutrino decay, the fundamental mechanism
underlying the process must be neutrino mass. Estimates of the mass required
suggest that this mechanism is less likely than the direct mechanism of
Majorana mass terms in the mass matrix.


title: MSW Implications of Solar Neutrino Experiments

abstract:
  I discuss the implications for future solar neutrino experiments of the most
recent gallium data in the context of the MSW mechanism. At the low energy end
of the solar neutrino spectrum we need to measure the $^7$Be component
directly; and at the high energy end, we need precise measurements of the shape
of the spectrum.