title: Comments on the Electroweak Phase Transition

abstract:
  We report on an investigation of various problems related to the theory of
the electroweak phase transition. This includes a determination of the nature
of the phase transition, a discussion of the possible role of higher order
radiative corrections and the theory of the formation and evolution of the
bubbles of the new phase. We find in particular that no dangerous linear terms
appear in the effective potential. However, the strength of the first order
phase transition is 2/3 times less than what follows from the one-loop
approximation. This rules out baryogenesis in the minimal version of the
electroweak theory.


title: A Natural Framework for Solar and 17 keV Neutrinos

abstract:
  Motivated by recent experimental claims for the existence of a 17 keV
neutrino and by the solar neutrino problem, we construct a class of models
which contain in their low-energy spectrum a single light sterile neutrino and
one or more Nambu-Goldstone bosons. In these models the required pattern of
breaking of lepton-number symmetry takes place near the electroweak scale and
all mass heirarchies are technically natural. The models are compatible with
all cosmological and astrophysical constraints, and can solve the solar
neutrino problem via either the MSW effect or vacuum oscillations. The deficit
in atmospheric muon neutrinos seen in the Kamiokande and IMB detectors can also
be explained in these models.


title: Towards the Theory of Cosmological Phase Transitions

abstract:
  We discuss recent progress (and controversies) in the theory of finite
temperature phase transitions. This includes the structure of the effective
potential at a finite temperature, the infrared problem in quantum statistics
of gauge fields, the theory of formation of critical and subcritical bubbles
and the theory of bubble wall propagation.


title:
The quest for low-energy supersymmetry and the role of high-energy
  $e^+e^-$ colliders

abstract:
  The motivations for low-energy supersymmetry and the main features of the
minimal supersymmetric extension of the Standard Model are reviewed. Possible
non-minimal models and the issue of gauge coupling unification are also
discussed. Theoretical results relevant for supersymmetric particle searches at
present and future accelerators are presented, with emphasis on the role of a
proposed $\epem$ collider with $\sqrt{s}
  = 500 \gev$. In particular, recent results on radiative corrections to
supersymmetric Higgs boson masses and couplings are summarized, and their
implications for experimental searches are discussed in some detail. (Plenary
talk at the Workshop on Physics and Experiments with Linear Colliders,
Saariselk\"a, Lapland, Finland, 9--14 September 1991)


title: Extended Color Models with a Heavy Top Quark

abstract:
  We present a class of models in which the top quark, by mixing with new
physics at a higher energy scale, is naturally heavier than the other standard
model particles. We take this new physics to be extended color. Our models
contain new particles with masses between 100 GeV and 1 TeV, some of which may
be just within the reach of the next generation of experiments. In particular
one of our models implies the existence of two right handed top quarks. These
models demonstrate the existence of a standard model-like theory consistent
with experiment, and leading to new physics below the TeV scale, in which the
third generation is treated differently than the first two.


title: Solutions to the strong CP problem in a world with gravity

abstract:
  We examine the sensitivity of several solutions of the strong-CP problem to
violations of global symmetries by Planck scale physics. We find that the
Peccei-Quinn solution is extremely sensitive to U(1)_PQ violating operators of
dimension less than 10. We construct models in which the PQ symmetry is
protected by gauge symmetries to the requisite level.


title: Differential Renormalization of Massive Quantum Field Theories

abstract:
  We extend the method of differential renormalization to massive quantum field
theories treating in particular $\ph4$-theory and QED. As in the massless case,
the method proves to be simple and powerful, and we are able to find, in
particular, compact explicit coordinate space expressions for the finite parts
of two notably complicated diagrams, namely, the 2-loop 2-point function in
$\ph4$ and the 1-loop vertex in QED.


title: Monopole annihilation at the electroweak scale---Not!

abstract:
  We examine the issue of monopole annihilation at the electroweak scale
induced by flux tube confinement, concentrating first on the simplest
possibility---one which requires no new physics beyond the standard model.
Monopoles existing at the time of the electroweak phase transition may trigger
$W$ condensation which can confine magnetic flux into flux tubes. However we
show on very general grounds, using several independent estimates, that such a
mechanism is impotent. We then present several general dynamical arguments
constraining the possibility of monopole annihilation through any confining
phase near the electroweak scale.


title: How Efficient Is The Langacker-Pi Mechanism of Monopole Annihilation?

abstract:
  We investigate the dynamics of monopole annihilation by the Langacker-Pi
mechanism. We find taht considerations of causality, flux-tube energetics and
the friction from Aharonov-Bohm scatteering suggest that the monopole
annihilation is most efficient if electromagnetism is spontaneously broken at
the lowest temperature ($T_{em} \approx 10^6 GeV$) consistent with not having
the monopoles dominate the energy density of the universe.


title: Precision bounds on $m_H$ and $m_t

abstract:
  We perform a fit to precise electroweak data to determine the Higgs and top
masses. Penalty functions taking into account their production limits are
included. We find ${\displaystyle m_H=65^{+245}_{-4}\ GeV}$ and ${\displaystyle
m_t=122^{+25}_{-20}\ GeV}$. However whereas the top $\chi^2$ distribution
behaves properly near the minimum, the Higgs $\chi^2$ distribution does not,
indicating a statistical fluctuation or new physics. In fact no significative
bound on the Higgs mass can be given at present. However, if the LEP accuracy
is improved and the top is discovered in the preferred range of top masses, a
meaningful bound on the Higgs mass could be obtained within the standard model
framework.


title:
Comment on ``Damping of energetic gluons and quarks in high-temperature
  QCD''

abstract:
  Burgess and Marini have recently pointed out that the leading contribution to
the damping rate of energetic gluons and quarks in the QCD plasma, given by
$\gamma=c g^2\ln(1/g)T$, can be obtained by simple arguments obviating the need
of a fully resummed perturbation theory as developed by Braaten and Pisarski.
Their calculation confirmed previous results of Braaten and Pisarski, but
contradicted those proposed by Lebedev and Smilga. While agreeing with the
general considerations made by Burgess and Marini, I correct their actual
calculation of the damping rates, which is based on a wrong expression for the
static limit of the resummed gluon propagator. The effect of this, however,
turns out to be cancelled fortuitously by another mistake, so as to leave all
of their conclusions unchanged. I also verify the gauge independence of the
results, which in the corrected calculation arises in a less obvious manner.


title: Spontaneous CP Violation at the Electroweak Scale

abstract:
  Utilizing results on the cosmology of anomalous discrete symmetries we show
that models of spontaneous CP violation can in principle avoid the domain wall
problem first pointed out by Zel'dovich, Kobzarev and Okun. A small but nonzero
$\theta_{QCD}$ explicitly breaks CP and can lift the degeneracy of the two CP
conjugate vacua through nonperturbative effects so that the domain walls become
unstable, but survive to cosmologically interesting epochs. We explore the
viability of spontaneous CP violation in the context of two Higgs models, and
find that the invisible axion solution of the strong CP problem cannot be
implemented without further extensions of the Higgs sector.


title: Solar Neutrino Data and Its Implications

abstract:
  The complete and concurrent Homestake and Kamiokande solar neutrino data sets
(including backgrounds), when compared to detailed model predictions, provide
no unambiguous indication of the solution to the solar neutrino problem. All
neutrino-based solutions, including time-varying models, provide reasonable
fits to both the 3 year concurrent data and the full 20 year data set. A simple
constant B neutrino flux reduction is ruled out at greater than the 4$\sigma$
level for both data sets. While such a flux reduction provides a marginal fit
to the unweighted averages of the concurrent data, it does not provide a good
fit to the average of the full 20 year sample. Gallium experiments may not be
able to distinguish between the currently allowed neutrino-based possibilities.


title: Strings, Textures, Inflation and Spectrum Bending

abstract:
  We discuss relationship between inflation and various models of production of
density inhomogeneities due to strings, global monopoles, textures and other
topological and non-topological defects. Neither of these models leads to a
consistent cosmological theory without the help of inflation. However, each of
these models can be incorporated into inflationary cosmology. We propose a
model of inflationary phase transitions, which, in addition to topological and
non-topological defects, may provide adiabatic density perturbations with a
sharp maximum between the galaxy scale $l_g$ and the horizon scale $l_H$.


title: Light Spin-One Particles Imply Gauge Invariance

abstract:
  Recently, calculations which consider the implications of anomalous trilinear
gauge-boson couplings, both at tree-level and in loop-induced processes, have
been criticized on the grounds that the lagrangians employed are not \gwk gauge
invariant. We prove that, in fact, the general Lorentz-invariant and $U(1)_\em$
invariant but {\it not} $SU_L(2)\times U_Y(1)$ invariant action is equivalent
to the general lagrangian in which $SU_L(2)\times U_Y(1)$ appears but is
nonlinearly realized. We demonstrate this equivalence in an explicit
calculation, and show how it is reconciled with loop calculations in which the
different formulations can (superficially) appear to give different answers. In
this sense any effective theory containing light spin-one particles is seen to
be automatically gauge invariant.


title: Uses and Abuses of Effective Lagrangians

abstract:
  Motivated by past and recent analyses we critically re-examine the use of
effective lagrangians in the literature to constrain new physics and to
determine the `physics reach' of future experiments. We demonstrate that many
calculations, such as those involving anomalous trilinear gauge-boson
couplings, either considerably overestimate loop-induced effects, or give
ambiguous answers. The source of these problems is the use of cutoffs to
evaluate the size of such operators in loop diagrams. In contrast to other
critics of these loop estimates, we prove that the inclusion of
nonlinearly-realized gauge invariance into the low-energy lagrangian is
irrelevant to this conclusion. We use an explicit example using known
multi-Higgs physics above the weak scale to underline these points. We show how
to draw conclusions regarding the nature of the unknown high-energy physics
without making reference to low-energy cutoffs.


title:
Multiple photon effects in fermion-(anti)fermion scattering at SSC
  energies

abstract:
  We use the theory of Yennie, Frautschi and Suura to realize, via Monte Carlo
methods, the process $f\,\bbbarf\to f'\,\bbbarf'+n\gamma$ at SSC and LHC
energies, where $f$ and $f'$ are quarks or leptons. QED infrared divergences
are canceled to all orders in perturbation theory. The resulting Monte Carlo
event generator, SSC-YFS2, is used to study the effects of initial-state photon
radiation on these processes in the SSC environment. Sample Monte Carlo data
are presented and discussed. We find that the respective multiple-photon
effects must be taken into account in discussing precise predictions for SSC
physics processes.


title:
Electroweak Symmetry Breaking via a Technicolor Nambu--Jona-Lasinio
  Model

abstract:
  We consider a theory of gauge fields and fermions which we argue gives rise
to dynamics similar to that of the Nambu--Jona-Lasinio (NJL) model when a gauge
coupling constant is appropriately fine-tuned. We discuss the application of
this model to dynamical electroweak symmetry breaking by a top-quark
condensate. In this model, custodial symmetry is violated solely by
perturbatively weak interactions, and the top--bottom mass splitting is due to
the enhanced sensitivity to custodial symmetry violation near the critical
point. We also consider models in which electroweak symmetry is broken by new
strongly- interacting fermions with NJL-like dynamics. We argue that these
models require additional fine-tuning in order to keep corrections to the
electroweak $\rho$-parameter acceptably small.


title: Aspects of Two-Photon Physics at Linear e+e- Colliders

abstract:
  We discuss various reactions at future e+e- and gamma-gamma colliders
involving real (beamstrahlung or backscattered laser) or quasi--real
(bremsstrahlung) photons in the initial state and hadrons in the final state.
The production of two central jets with large pT is described in some detail;
we give distributions for the rapidity and pT of the jets as well as the
di--jet invariant mass, and discuss the relative importance of various initial
state configurations and the uncertainties in our predictions. We also present
results for `mono--jet' production where one jet goes down a beam pipe, for the
production of charm, bottom and top quarks, and for single production of W and
Z bosons. Where appropriate, the two--photon processes are compared with
annihilation reactions leading to similar final states. We also argue that the
behaviour of the total inelastic gamma-gamma cross section at high energies
will probably have little impact on the severity of background problems caused
by soft and semi--hard (`minijet') two--photon reactions. We find very large
differences in cross sections for all two--photon processes between existing
designs for future e+e- colliders, due to the different beamstrahlung spectra;
in particular, both designs with <<1 and >>1 events per bunch crossing exist.


title: Test of the Dimopouos-Hall-Raby Ansatz for Fermion Mass Matrices

abstract:
  By evolution of fermion mass matrices of the Fritzsch and the Georgi-Jarlskog
forms from the supersymmetric grand unified scale, DHR obtained predictions for
the quark masses and mixings. Using Monte Carlo methods we test these
predictions against the latest determinations of the mixings, the CP-violating
parameter epsilon_K and the B_d^0--Bbar_d^0 mixing parameter r_d. The
acceptable solutions closely specify the quark masses and mixings, but lie at
the edges of allowed regions at 90% confidence level.


title: Improved Heavy Quark Effective Theory Currents

abstract:
  It is hoped that the accuracy of a variety of lattice calculations will be
improved by perturbatively eliminating effects proportional to the lattice
spacing. In this paper, we apply this improvement program to the heavy quark
effective theory currents which cause a heavy quark to decay to a light quark,
and renormalize the resulting operators to order $\alphaS$. We find a small
decrease in the amount that the operator needs to be renormalized, relative to
the unimproved case.


title: Infrared Factorization, Wilson Lines and the Heavy Quark Limit

abstract:
  It is shown that, in QCD, the same universal function
$\Gamma_{cusp}(\vartheta, \alpha_\s)$ determines the infrared behaviour of the
on-shell quark form factor, the velocity-dependent anomalous dimension in the
heavy quark effective field theory (HQET) and the renormalization properties of
the vacuum averaged Wilson lines with a cusp. It is demonstrated that a
combined use of the methods developed in the relevant different branches of
quantum field theory essentially facilitates the all-order study of the
asymptotic and analytic properties of this function.


title:
Testing the Higgs Sector of the Minimal Supersymmetric Standard Model at
  Large Hadron Colliders

abstract:
  We study the Higgs sector of the Minimal Supersymmetric Standard Model, in
the context of proton-proton collisions at LHC and SSC energies. We assume a
relatively heavy supersymmetric particle spectrum, and include recent results
on one-loop radiative corrections to Higgs-boson masses and couplings. We begin
by discussing present and future constraints from the LEP experiments. We then
compute branching ratios and total widths for the neutral ($h,H,A$) and charged
($H^\pm$) Higgs particles. We present total cross-sections and event rates for
the important discovery channels at the LHC and SSC. Promising physics
signatures are given by $h \to \gamma \gamma$, $H \to \gamma \gamma$ or $Z^*
Z^*$ or $\tau^+ \tau^-$, $A \to \tau^+ \tau^-$, and $t \to b H^+$ followed by
$H^+ \to \tau^+ \nu_{\tau}$, which should allow for an almost complete coverage
of the parameter space of the model.


title: Phenomenology of R-Parity Breaking in E6 Models

abstract:
  We explore the phenomenology of new R-parity violating operators that can
occur in E6 models. The set of allowed operators is found to depend sensitively
on the nature of the extension of the standard model gauge group. These new
interactions lead to additional production processes for the exotic particles
in such models and allow the LSP to decay but with a highly suppressed rate.
The implications of these new interations are examined for the Tevatron, SSC,
LHC, HERA, and sqrt{s} = 0.5 and 1 TeV e+e- colliders.


title:
Chiral perturbation theory for hadrons containing a heavy quark: the
  sequel

abstract:
  Charm and bottom mesons and baryons are incorporated into a low energy chiral
Lagrangian. Interactions of the heavy hadrons with light octet Goldstone bosons
are studied in a framework which represents a synthesis of chiral perturbation
theory and the heavy quark effective theory. The differential decay rate for
the semileptonic process $\LBzero \to \Sigma_c^{++} + e^- + \bar{\nu}_e +
\pi^-$ is calculated at the zero recoil point using this hybrid formalism.


title:
Rotation Curves of Spiral Galaxies and Large Scale Structure of Universe
  under Generalized Einstein Action

abstract:
  We consider an addition of the term which is a square of the scalar curvature
to the Einstein-Hilbert action. Under this generalized action, we attempt to
explain i) the flat rotation curves observed in spiral galaxies, which is
usually attributed to the existence of dark matter, and ii) the contradicting
observations of uniform cosmic microwave background and non-uniform galaxy
distributions against redshift. For the former, we attain the flatness of
velocities, although the magnitudes remain about half of the observations. For
the latter, we obtain a solution with oscillating Hubble parameter under
uniform mass distributions. This solution leads to several peaks of galaxy
number counts as a function of redshift with the first peak corresponding to
the Great Wall.


title: Electroweak Breaking in Supersymmetric Models

abstract:
  We discuss the mechanism for electroweak symmetry breaking in supersymmetric
versions of the standard model. After briefly reviewing the possible sources of
supersymmetry breaking, we show how the required pattern of symmetry breaking
can automatically result from the structure of quantum corrections in the
theory. We demonstrate that this radiative breaking mechanism works well for a
heavy top quark and can be combined in unified versions of the theory with
excellent predictions for the running couplings of the model. (To be published
in ``Perspectives in Higgs Physics'', G. Kane editor.)


title: Intermediate and Heavy Higgs Boson Physics at a 0.5 TeV e^+ e^- Collider

abstract:
  We explore the potential of a future e^+ e^- collider in the 0.5 TeV
center-of-mass energy range to detect intermediate or heavy Higgs bosons in the
Standard Model. We first briefly assess the production cross sections and
update the decay branching fractions for a Higgs boson of intermediate mass,
with M_Z < m_H < 2M_W. We then study in detail the possibility of detecting a
heavy Higgs boson, with m_H > 2M_W, through the production of pairs of weak
bosons. We quantitatively analyze the sensitivity of the process e^+ e^- --> nu
nubar W^+ W^- (ZZ) to the presence of a heavy Higgs-boson resonance in the
Standard Model. We compare this signal to various backgrounds and to the
smaller signal from e^+ e^- --> ZH --> mu^+ mu^- W^+ W^- (ZZ), assuming the
weak-boson pairs to be detected and measured in their dominant hadronic decay
modes W^+ W^- (ZZ) --> 4jets. A related Higgs-boson signal in 6-jet final
states is also estimated. We show how the main backgrounds from e^+ e^- W^+ W^-
(ZZ), e nu WZ, and t tbar production can be reduced by suitable acceptance
cuts. Bremsstrahlung and typical beamstrahlung corrections are calculated.
These corrections reduce Higgs-boson production by scattering mechanisms but
increase production by annihilation mechanisms; they also smear out some
dynamical features such as Jacobian peaks in p_T(H). With all these corrections
included, we conclude that it should be possible to detect a heavy Higgs-boson
signal in the nu nubar W^+ W^-(ZZ) channels up to mass m_H=350 GeV.


title: Probing the $WW\gamma$ Vertex in $e^\pm p\to\nu\gammaX$

abstract:
  We study the prospects of testing the $WW\gamma$ vertex in $e^- p\to\nu\gamma
X$ and $e^+ p\to\nu\gamma X$ at HERA and LEP/LHC. Destructive interference
effects between the Standard Model and the anomalous contributions to the
amplitude severely limit the sensitivity of both processes to non-standard
$WW\gamma$ couplings. Sensitivity limits for the anomalous $WW\gamma$ couplings
$\kappa$ and $\lambda$ at HERA and LEP/LHC are derived, taking into account
experimental cuts and uncertainties, and the form factor behaviour of
nonstandard couplings. These limits are found to be significantly weaker than
those which can be expected from other collider processes within the next few
years. At HERA, they are comparable to bounds obtained from $S$-matrix
unitarity.


title: A Tumbling Top-Quark Condensate Model

abstract:
  We propose a renormalizable model with no fundamental scalars which breaks
itself in the manner of a "tumbling" gauge theory down to the standard model
with a top-quark condensate. Because of anomaly cancellation requirements, this
model contains two color sextet fermions (quixes), which are vector-like with
respect to the standard model gauge group. The model also has a large number of
pseudo-Nambu-Goldstone bosons, some of which can be light. The top-quark
condensate is responsible for breaking the electroweak gauge symmetry and gives
the top quark a large mass. We discuss the qualitative features and instructive
shortcomings of the model in its present form. We also show that this model can
be naturally embedded into an aesthetically pleasing model in which the
standard model fermion families appear symmetrically.


title: Supersymmetry Protects the Primordial Baryon Asymmetry

abstract:
  It has been argued that any primordial B+L asymmetry existing at very high
temperatures can be subsequently erased by anomalous electroweak effects. We
argue that this is not necessarily the case in the supersymmetric standard
model because, apart from B and/or L, there are, above a certain temperature
$T_{SS}$, two other anomalous U(1) currents. As a consequence, anomalous
electroweak effects are only able to partially transform a B+L excess into a
generation of primordial sparticle (e.g. gaugino) density. This relaxes recent
bounds on B,L-violating non-renormalizable couplings by several orders of
magnitude. In particular, dimension-5 couplings inducing neutrino masses may be
4 orders of magnitude larger than in the non-supersymmetric case, allowing for
neutrino masses of the order of 10 eV. These values are consistent with a
MSW+see-saw explanation of the solar-neutrino data and also with possible
neutrino oscillations measurable at accelerators. Cosmological bounds on other
rare processes, such as neutron-antineutron oscillations get also relaxed by
several orders of magnitude compared with previous estimates.


title: Heavy Mesons in Two Dimensions

abstract:
  The large mass limit of QCD uncovers symmetries that are not present in the
QCD lagrangian. These symmetries have been applied to physical (finite mass)
systems, such as B and D mesons.
  We explore the validity of this approximation in the 't Hooft model
(two-dimensional QCD in the large-N approximation). We find that the large mass
approximation is good, even at the charm mass, for form factors, but it breaks
down for the pseudoscalar decay constant.


title: Chiral Perturbation Theory for $f_{D_S}/f_D$ and $B_{B_S}/B_{B}$

abstract:
  The decay constants for the $D$ and $D_S$ mesons, denoted $f_D$ and $f_{D_S}$
respectively, are equal in the $SU(3)_V$ limit, as are the hadronic amplitudes
for $B_S-\bar B_S$ and $B^0-\bar B^0$ mixing. The leading $SU(3)_V$ violating
contribution to $\left( f_{D_S} / f_D \right)$ and to the ratio of hadronic
matrix elements relevant for $B_S-\bar B_S$ and $B^0-\bar B^0$ mixing
amplitudes are calculated in chiral perturbation theory. We discuss the
formalism needed to include both meson and anti-meson fields in the heavy quark
effective theory.


title: An Introduction to Spin Dependent Deep Inelastic Scattering

abstract:
  The main focus of these lectures is on those aspects of deep inelastic
scattering that can be derived directly from QCD using quantum field theory,
without recourse to phenomenological models. The emphasis is on spin dependent
scattering, but the theory of spin averaged scattering is also discussed. A
detailed analysis is given for the case of spin 1/2 targets, with a brief
discussion of higher spin targets at the end. The QCD derivation of the
Callan-Gross relation, the longitudinal structure function $F_L$, and the
Bjorken and Ellis-Jaffe sum rules is presented. I also discuss the
Wilczek-Wandzura contribution to $g_2$, and why the Gottfried sum rule does not
hold in QCD.


title:
4-dimensional spontaneously broken U(1)L gauge theories with a composite
  Wess-Zumino field

abstract:
  Some spontaneously broken gauge theories with left couplings to fermions,
like the abelian model that we propose here, can be endowed with a composite
scalar sector and Wess-Zumino field ; their quantization in the functionnal
integral formalism accordingly requires the introduction of constraints that,
together with the breaking of the gauge symmetry by the scalars, and among
other consequences, give the Higgs field and the fermions (quarks) infinite
masses; this makes them unobservable. Gauge invariance and unitarity are
achieved through a derivative coupling of the W-Z field to the fermionic
current; the anomaly gets cancelled in the above infinite fermion mass limit.
We show how the problems of renormalizability are evaded at the one-loop level
by resumming diagrams at the ladder approximation and reshuffling the
perturbative series, and because the fermionic current is conserved. The
Wess-Zumino field can be "gauged away" to become the 3rd polarization of the
massive gauge field; the pseudoscalar partner of the Higgs, tightly linked to
the W-Z field, behaves like an abelian pion. In particular, no extra scale of
interaction has to be introduced, unlike in "technicolour" theories. Problems
concerning the leptonic sector are only mentionned.


title:
Comment on ``High Temperature Fermion Propagator -- Resummation and
  Gauge Dependence of the Damping Rate''

abstract:
  Baier et al. have reported the damping rate of long-wavelength fermionic
excitations in high-temperature QED and QCD to be gauge-fixing-dependent even
within the resummation scheme due to Braaten and Pisarski. It is shown that
this problem is caused by the singular nature of the on-shell expansion of the
fermion self-energy in the infra-red. Its regularization reveals that the
alleged gauge dependence pertains to the residue rather than the pole of the
fermion propagator, so that in particular the damping constant comes out
gauge-independent, as it should.


title:
Effective Field Theory of Anomalous Gauge-Boson Couplings at High-Energy
  pp Colliders

abstract:
  We compute the effects of anomalous gauge-boson couplings at high-energy
hadron colliders using next-to-leading order $SU(2) \times SU(2)$ chiral
perturbation theory. By comparing the yields from the universal $p^2$ terms
with those arising from new physics at order $p^4$, we estimate the sensitivity
of the SSC and LHC to the indirect effects of electroweak symmetry breaking.


title: Quark solitons as constituents of hadrons

abstract:
  We exhibit static solutions of multi-flavour QCD in two dimensions that have
the quantum numbers of baryons and mesons, constructed out of quark and
anti-quark solitons. In isolation the latter solitons have infinite energy,
corresponding to the presence of a string carrying the non-singlet colour flux
off to spatial infinity. When $N_c$ solitons of this type are combined, a
static, finite-energy, colour singlet solution is formed, corresponding to a
baryon. Similarly, static meson solutions are formed out of a soliton and an
anti-soliton of different flavours. The stability of the mesons against
annihilation is ensured by flavour conservation. The static solutions exist
only when the fundamental fields of the bosonized Lagrangian belong to
$U(N_c{\times}N_f)$ rather than to $SU(N_c) \times U(N_f)$. Discussion of
flavour symmetry breaking requires a careful treatment of the normal ordering
ambiguity. Our results can be viewed as a derivation of the constituent quark
model in QCD$_2$, allowing a detailed study of constituent mass generation and
of the heavy quark symmetry.


title: Scalar--Tensor Theories of Gravity with \PHI Dependent Masses

abstract:
  We study new physical phenomena and constraints in generalized scalar--tensor
theories of gravity with $\Phi$--dependent masses. We investigate a scenario
(which can arise in string theories) with two types of $\Phi$--dependent masses
which could correspond to visible and dark matter sectors. The parameters of
this theory are constrained from post--Newtonian bounds, primordial
nucleosynthesis and the age of the Universe. We present a perfect fluid
formalism for the dark matter sector with variable masses and find an entropy
increase effect during the matter era and, in principle, a measurable effect on
the motion of the halo of spiral galaxies. For the case of string effective
theories, the constancy of gauge couplings provide new bounds which are orders
of magnitude stronger than the previous ones.


title: Non-Oblique Effects in the Z b b_bar Vertex from ETC Dynamics

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


abstract:
  A new ansatz for quark and lepton mass matrices is proposed in the context of
supersymmetric grand unified theories. The 13 parameters describing fermion
masses and mixings are determined in terms of only 6 free parameters, allowing
7 testable predictions. The values of $V_{us}$, $V_{cb}$, $V_{ub}$, $m_u$,
$m_d$, $m_s$, and $m_b$ are then predicted as a function of the 3 charged
lepton masses, $m_c$, $m_t$, and $\tan \beta$, the ratio of Higgs vacuum
expectation values. In particular the Cabibbo angle and $m_s/m_d$ are
determined in terms of only lepton masses. All predictions are in very good
agreement with experiments.


title: Resummation in a Hot Scalar Field Theory

abstract:
  A resummed perturbative expansion is used to obtain the self-energy in the
high-temperature \(g^2\phi^4\) field theory model up to order $g^4$. From this
the zero momentum pole of the effective propagator is evaluated to determine
the induced thermal mass and damping rate for the bosons in the plasma to order
$g^3$. The calculations are performed in the imaginary time formalism and a
simple diagrammatic analysis is used to identify the relevant diagrams at each
order. Results are compared with similar real-time calculations found in the
literature.


title: Two--Body Decays of $B_s$ Mesons

abstract:
  We have calculated the decay rates of the $B_s$ meson in a number of
exclusive two--body decay channels using the Bauer--Stech--Wirbel model for
current matrix elements. The influence of the free parameters of the model on
the predictions is studied. The total branching ratio of the $B_s$ into final
states which only contain stable charged particles is found to be about
$10^{-3}$.


title: On the Renormalization of the S Parameter

abstract:
  We calculate the S parameter of the standard model at one loop of fermions,
using three different regularizations (dimensional, Pauli-Villars and lattice)
and find an extra contribution to the S parameter besides the standard one for
each case. This shows that the extra contribution recently reported for the
lattice regularization is {\it not} necessarily tied to the non-decoupling
effect of fermion doublers. We argue that the extra contribution should be
subtracted in the renormalizable perturbative expansion.


title: A QCD Calculation of the Interaction of Quarkonium with Nuclei

abstract:
  The interaction of quarkonium with nuclei is studied in the $m_Q\rightarrow
\infty$ limit of QCD, where the binding energy is found to be exactly
computable. The dominant contribution to the interaction is from two-gluon
operators. The forward matrix elements of these two-gluon operators can be
determined from the QCD scale anomaly, and from deep inelastic scattering. We
apply our results to the $\Upsilon$ and $J/\psi$, treating the $\qqbar$
interaction as purely Coulombic. We find the $\Upsilon$ binds in nuclear matter
with a binding energy of a few $\mev$, while for the $J/\psi$ binding is of
order 10 $\mev$. For the $J/\psi$ in particular we expect confinement effects
to produce large corrections to this result.


title: Colored Pseudo-Goldstone Bosons and Gauge Boson Pairs

abstract:
  If the electroweak symmetry breaking sector contains colored particles
weighing a few hundred GeV, then they will be copiously produced at a hadron
supercollider. Colored technipions can rescatter into pairs of gauge bosons. As
proposed by Bagger, Dawson, and Valencia, this leads to gauge boson pair rates
far larger than in the standard model. In this note we reconsider this
mechanism, and illustrate it in a model in which the rates can be reliably
calculated. The observation of both an enhanced rate of gauge-boson-pair events
and colored particles would be a signal that the colored particles were
pseudo-Goldstone bosons of symmetry breaking.


title:
QCD renormalization for the top-quark mass in a mass geometrical mean
  hierarchy

abstract:
  $QCD$ renormalization for the top-quark mass is calculated in a mass
geometrical mean hierarchy, $m_d m_b = m_s^2$ and $m_u m_t = m_c^2$. The
physical mass, $m_t(m_t) = 160 {\pm} 50 GeV$ is obtained, which agrees very
well with electroweak precision measurement.


title: Unusual high-pT jet events at HERA

abstract:
  We calculate the cross-section for events at HERA where the proton loses only
a minute fraction of its initial energy, all of which goes into producing a
single pair of transverse jets.


title: On tunneling at finite energies and temperatures

abstract:
  We study the contribution of finite energy tunneling to the total vacuum
transition rate in a system at finite temperature. We find that in certain
models, such as the 1+1 Abelian Higgs model, the quantum contribution is
non-negligible even at large temperatures. We show how the persistence of the
cosmological baryon asymmetry yields a bound on the inclusive two particle
cross section in the anomalous (B violating) sector.


title: Proton $\beta% decay in large magnetic fields

abstract:
  A delicate interplay between the anomalous magnetic moments of the proton and
neutron makes, in magnetic fields $B\ge 2\times 10^{14}$ T, the neutron stable
and for fields $B\ge 5\times 10^{14}$ T the proton becomes unstable to a decay
into a neutron via $\beta$ emission. Limits on the field strengths for which
these arguments hold are presented and are related to questions of vacuum
stability in the presence of such fields. Possible astrophysical consequences
are discussed.


title:
Mass and mixing angle patterns in the Standard Model and its Minimal
  Supersymmetric Extension

abstract:
  Using renormalization group techniques, we examine several interesting
relations among masses and mixing angles of quarks and leptons in the Standard
Model. We extend the analysis to the minimal supersymmetric extension to
determine its effect on these mass relations. Remarkably Supersymmetry allows
for these relations to be satisfied at a single grand unified scale.


title: Signals for Virtual Leptoquark Exchange at HERA

abstract:
  We study the effects of virtual leptoquarks on charged current and neutral
current processes at the $ep$ collider HERA. We present the areas of parameter
space that can be excluded at HERA by searching for deviations from Standard
Model expectations. The best results are obtained by examining the ratio of
neutral current to charged current cross sections, $R=\sigma_{NC}/\sigma_{CC}$,
where, with $200\inpb$ of integrated luminosity for unpolarized $e^-$ and $e^+$
beams, HERA can search for leptoquarks with masses up to $\sim 800\gev$, with
leptoquark coupling strengths of order $\alpha_{em}$.


title: Superconductivity Solves the Monopole Problem for Alice Strings

abstract:
  Alice strings are cosmic strings that turn matter into antimatter. Although
they arise naturally in many GUT's, it has long been believed that because of
the monopole problem they can have no cosmological effects. We show this
conclusion to be false; by using the Langacker-Pi mechanism, monopoles can in
fact be annihilated while Alice strings are left intact. This opens up the
possibility that they can after all contribute to cosmology, and we mention
some particularly important examples.


title: Phase Transition Temperatures at Next-to-Leading Order

abstract:
  Broken gauge symmetries are typically restored at high temperature, and the
leading-order result for the critical temperature $T_c$ was found many years
ago by Weinberg and by Dolan and Jackiw. I find a simple expression for the
next-to-leading order correction to $T_c$, which is order $e T_c$ where $e$ is
the gauge coupling. The result is a simple consequence of recent work on
summing ring diagrams at high temperature in gauge theories. The result is
valid when the Higgs self-coupling $\lambda$ is the same order as $e^2$, and it
does not address the case of strongly first-order phase transitions, which
arise when $\lambda \ll e^2$.


title: The Residual Mass Term in the Heavy Quark Effective Theory

abstract:
  We reformulate the heavy quark effective theory in the presence of a residual
mass term, which has been taken to vanish in previous analyses. While such a
convention is permitted, the inclusion of a residual mass allows us to resolve
a potential ambiguity in the choice of the expansion parameter which defines
the effective theory. We show to subleading order in the mass expansion that
physical quantities computed in the effective theory do not depend on the
expansion parameter.


title: Confinement in a Chromoelectric Vacuum

abstract:
  A chromoelectric vacuum that confines both gluon and quark degrees of freedom
(in the sense that they do not exist as asymptotic states) is constructed.
However some degrees of freedom still exist as asymptotic states thereby
allowing colour singlets to propagate.


title: Reaction rate in a heat bath

abstract:
  We show in detail how the presence of a heat bath of photons effectively
gives charged particles in the final state of a decay process a
temperature-dependent mass, and changes the effective strength of the force
responsible for the decay. At low temperature, gauge invariance causes both
these effects to be largely cancelled by absorption of photons from the heat
bath and by stimulated emission into it, but at high temperature the
temperature-dependent mass is the dominant feature.


title: New Tools for Analyzing Quark Mixing

abstract:
  We present some new mathematical tools which help to derive information about
the quark mass matrices directly from experimental data and to elucidate the
structure of these mass matrices.


title:
CP-violating Phenomena in an $ SU(2)_L \times SU(2)_R \times U(1)_{B-L}
  \times SU(3)_H^{VL}$ Horizontal Symmetric Model

abstract:
  We consider an $SU(2)_L \times SU(2)_R \times U(1)_{B-L} \times SU(3)_H^{VL}$
gauge model with natural flavour conservation in the Higgs sector, in which
CP-violation occurs due to the horizontal interactions only. We calculate the
CP-violating observables $\epsilon$ and $\epsilon'$ of the neutral kaon sector
and $d_n$, the electric dipole moment of the neutron. The regions of the
parameter space which yield a value of $\epsilon$ that is in agreement with the
experiment, lead to predictions for $\epsilon'$ and $d_n$ which are at least
five orders of magnitude smaller than the current experimental upper bounds.


title:
Threshold Effects in SO(10) Grandunified Models and Solar Neutrino
  Puzzle

abstract:
  We compute the threshold uncertainties due to unknown masses of the Higgs
bosons on the predictions for the intermediate and unification scales, $M_I$
and $M_U$ respectively in SO(10) models.We focus on models with separate
breaking scales for Parity and $SU(2)_R$ symmetries since they provide a
natural realization of the see-saw mechanism for neutrino masses. For the two
step symmetry breaking chains ,where left-right symmetric gauge groups appear
at the intermediate scale, we find that parity invariance of the theory at the
unification scale drastically reduces the GUT threshold effects in some cases.
Including the effects of the intermediate scale thresholds ,we compute the
uncertainty in the above mass scales and study their implications for proton
lifetime and neutrino masses. An important outcome of our analysis is that if
the currently favored nonadiabatic MSW solution to the solar neutrino puzzle is
accepted , it will rule out the $SU(2)_LXSU(2)_RXU(1)_{B-L}X SU(3)_c$ as an
intermediate symmetry for SO(10) breaking whereas the intermediate symmetry
$SU(2)_LXSU(2)_RXSU(4)_c$, is quite consistent with it.


title:
Ginzburg-Landau Theory of the Electroweak Phase Transition and
  Analytical Results

abstract:
  The phase transition of the electroweak vacuum induced by a strong magnetic
field is examined, and a connection is made with the Ginzburg-Landau theory of
type-II superconductivity. For solutions of the exact nonlinear field equations
of the electroweak theory with lattice periodicity in directions perpendicular
to the magnetic field, it is proven that, likewise, each lattice cell must
enclose an integer number of quanta of magnetic flux. Close to the lower
critical magnetic field, a perturbative method developed by MacDowell and the
author is used to study properties of the lattice solutions. Analytical
expressions for observables are obtained in terms of a complex parameter $\tau$
specifying the lattice and it is shown that the triangular Abrikosov solution
constitutes a local minimum of the energy provided $M_H > M_Z$.
  PACS numbers: 11.15.Kc, 11.15.Ex, 74.60.-w, 05.70.Fh


title: The Propagation of Quarks in the Spatial Direction in Hot QCD

abstract:
  The dynamics of {\it light} fermions propagating in a spatial direction at
high temperatures can be described effectively by a two--dimensional
Schr\"odinger equation with {\it heavy} effective mass $m_{\rm eff} = \pi T$.
Starting from QED, we discuss the transition from three-- to two--dimensional
positronium discussing the latter in detail including relativistic effects. In
the case of QCD the problem is similar to that of heavy quarkonium. Our
effective potential contains the usual Coulomb and confining parts as well as a
perturbative spin--spin interaction. The resulting $\bar q q$ ``wave functions"
reproduce recent lattice data for the $\rho$ and $\pi$ channels. The physical
meaning of such `confinement' is related to the non--trivial magnetic
interaction of color currents in the quark--gluon plasma. Our results do not
contradict the idea that the normal electric interaction of color charges is
screened and produces no bound states in the usual sense.


title:
Heavy Hadron Form Factor Relations for $m_c\ne\infty$ and
  $\bas(m_c)\ne0$

abstract:
  First order power corrections to current matrix elements between heavy meson
or $\Lambda_\Q$ baryon states are shown to vanish at the zero recoil point to
all orders in QCD. Five relations among the six form factors that parametrize
the semileptonic decay $\Lambda_b \to \Lambda_c e \overline{\nu}$ are also
demonstrated to exist to all orders in the strong coupling at order $1/\mQ$ .
The $O(\bas(m_c)/m_c)$ form factor relations are displayed.


title: Semileptonic $B_c$ Decay and Heavy Quark Spin Symmetry

abstract:
  Semileptonic decay of the $B_c$ meson is studied in the heavy quark limit.
The six possible form factors for $B_c \rightarrow B_s (B^0),B_s^* (B^{*0})$
semileptonic decay are determined by two invariant functions. Only one of these
functions contributes at zero recoil, where it is calculable to lowest order in
an operator product expansion in terms of the meson decay constant $f_B$ and
the $B_c$ wavefunction. A similar result is found for $B_c \rightarrow
D^0,D^{*0}$ and for $B_c\rightarrow\eta_c,J/\psi$ semileptonic decay for a
restricted kinematic region. Semileptonic $B_c$ decay provides a means for
determining the KM mixing angle $|V_{ub}|$.


title:
Virtual bremsstrahlung from pions and quarks in thermalized hadronic
  matter

abstract:
  A soft photon approximation is used to calculate the rates of lepton pair
production through virtual bremsstrahlung from both pions and quarks. Standard
assumptions about the evolution of a nuclear system under collision allow pion
and quark driven total production to be calculated. Comparisons are made with
Dalitz decay of light mesons. These mechanisms are expected to be significant
contributors to the soft dilepton mass spectra one might observe in heavy ion
collisions at RHIC and LHC energies.


title:
Production of the Lightest Supersymmetric Particle in Electron-Photon
  Collisions

abstract:
  We present cross sections for the production of the lightest supersymmetric
particle as a neutralino state in the minimal supersymmetric standard model at
electron-photon colliders. The lightest supersymmetric particle mass is taken
at a value of 30 GeV which is slightly higher than its lowest experimental
bound of 20 GeV, and the masses of the scalar electron are varied. We show
partial cross sections of the energy and angular distribution of the outgoing
electron for different values of the centre of mass energy. As a result we show
that electron-photon collider experiments could be quite sensitive to the
detection of supersymmetric particles.


title: Is CP a Gauge Symmetry?

abstract:
  We suggest here that CP is a discrete {\it gauge} symmetry, and is therefore
not violated by quantum gravity. We show that four dimensional CP can arise as
a discrete gauge symmetry in theories with dimensional compactification, if the
original number of Minkowski dimensions equals $8k+1$, $8k+2$ or $8k+3$, and if
there are certain restrictions on the gauge group; these conditions are met by
superstrings. CP may then be broken spontaneously below $10^9$ GeV, explaining
the observed CP violation in the kaon system without inducing a large EDMN. We
discuss the phenomenology of such models, as well as the peculiar nature of
cosmic ``CP strings'' which could be produced at the compactification scale.
Such strings have the curious property that a particle carried around the
string is turned into its CP conjugate. A single CP string renders four
dimensional spacetime nonorientable.


title: A Realistic Technicolor Model from 150 TeV down

abstract:
  A realistic technicolor model is presented with the dynamics below $150$ TeV
treated explicitly. Electroweak symmetry is broken by the condensates of a
`minimal' doublet of technifermions. The new feature of the model is that the
the third generation quarks are unified with the technifermions into multiplets
of a walking gauge force down to a scale of $10$ TeV. The remaining quarks and
leptons are not involved in this unification however. The walking dynamics
enhances the higher dimension interactions which give the ordinary fermions
their masses and mixing, while leaving flavor-changing neutral currents
suppressed. Because the third generation quarks actually feel the walking force
their masses can be much larger than those of the other quarks and the leptons.
The only non-standard particles with masses below several TeV are the single
doublet of technifermions, so electroweak radiative corrections are estimable
and within experimental limits.


title: Vacuum Alignment in "Composite Technicolor" Models

abstract:
  We consider the question of vacuum alignment in the recently proposed
"composite technicolor" (CTC) models. In order for these models to work, an
"ultrafermion" condensate must align in a particular way, driven by the
competition between ultrafermion masses and "flavor" gauge boson exchange. We
show that for ultrafermion masses large enough to explain the top quark mass,
order-of-magnitude estimates are sufficient to establish that the required
vacuum alignment cannot occur for perturbative values of the flavor gauge
couplings. If the top quark gets its mass from some other mechanism, a detailed
calculation is required. Using spectral function sum rules and a vector-meson
saturation approximation which is known to work well in QCD, we determine the
correct vacuum for this case in a limit where the flavor gauge bosons are
weakly coupled and the number of ultracolors $N$ is large. We again find that
the vacuum required by CTC models does not occur for perturbative values of the
flavor gauge couplings. We conclude that there is no evidence that the vacuum
aligns as required in CTC models.


title: Field Theory Without Feynman Diagrams: One-Loop Effective Actions

abstract:
  In this paper the connection between standard perturbation theory techniques
and the new Bern-Kosower calculational rules for gauge theory is clarified. For
one-loop effective actions of scalars, Dirac spinors, and vector bosons in a
background gauge field, Bern-Kosower-type rules are derived without the use of
either string theory or Feynman diagrams. The effective action is written as a
one-dimensional path integral, which can be calculated to any order in the
gauge coupling; evaluation leads to Feynman parameter integrals directly,
bypassing the usual algebra required from Feynman diagrams, and leading to
compact and organized expressions. This formalism is valid off-shell, is
explicitly gauge invariant, and can be extended to a number of other field
theories.


title: R parity can spontaneously break

abstract:
  We refute the claims made by Chaichian and Smilga in a recent paper in Phys
Rev Letters on the impossibility of spontaneous R Parity breaking. Apart from
explaining their error we summarize the results of a more detailed work that
demonstrates explicitly that R parity can break spontaneously at a scale
anywhere in the range 10 GeV to 1 Tev in a simple extension of the minimal SUSY
standard model proposed previously.


title:
Contributions to the W-Boson Anomalous Moments in the Two-Higgs-Doublet
  Model at Collider Energies

abstract:
  We examine the one loop contributions arising in the Two-Higgs-Doublet Model
(THDM) to the W-boson anomalous magnetic dipole and electric quadrupole form
factors for both photon and Z couplings relevant at collider energies. While
the model parameter and $q^2$-dependencies of these form factors are found to
be significant, the corresponding size of these corrections are relatively
small in comparison to unity. They are, however, found to be comparable in
magnitude to the usual Standard Model loop corrections. Radiative corrections
to the Higgs particle masses and couplings due to heavy top-quarks are included
in the analysis.


title: Late time Cosmological Phase Transition and Galactic Halo as Bose-liquid

abstract:
  We consider the ultra light pseudo Nambu-Goldstone boson appearing in the
late time cosmological phase transition theories as a dark matter candidate.
Since it is almost massless, its nature is more wave like than particle like.
Hence we apply quantum mechanics to study how they form the galactic halos.
Three predictions are made; (1)the mass profile $\rho\sim r^{-1.6}$, (2)there
are ripple-like fine structures in rotation curve, (3) the rotation velocity
times ripple's wave length is largely galaxy independent. We compare the
rotation curves predicted by our theory with the data observed.


title: Supersymmetric Signals in Electron-Photon Collision

abstract:
  Associated selectron-neutralino production in the process $e^-\gamma\to\tilde
e^-\tilde\chi^0$ provides a striking supersymmetric signal: events with a
single high $p_\perp$ electron and otherwise only invisible particles. For
$e^-\gamma$ collisions obtained at high energy linear colliders through
back-scattering of a laser beam, this reaction is shown to be complementary to
selectron pair production in the processes $e^+e^-\to\tilde e^+\tilde e^-$ and
$e^-e^-\to\tilde e^-\tilde e^-$, and to be a probe of heavy selectrons beyond
the kinematical limit of pair production. The standard model background from
$e^-\gamma\to e^-Z^0$ and $W^-\nu$ is studied and substantially reduced by
rapidity and transverse momentum cuts. The minimum required integrated
luminosities for observing this \susic\ signal are given as functions of
several model parameters and collider energies.


title: The Chiral Anomaly in Non-Leptonic Weak Interactions

abstract:
  The interplay between the chiral anomaly and the non-leptonic weak
Hamiltonian is studied. The structure of the corresponding effective Lagrangian
of odd intrinsic parity is established. It is shown that the factorizable
contributions (leading in $1/N_C$) to that Lagrangian can be calculated without
free parameters. As a first application, the decay $K^+ \ra \pi^+ \pi^0 \gamma$
is investigated.


title: Quark-Antiquark Regge Trajectories in Large N_c QCD

abstract:
  We apply methods developed by Lovelace, Lipatov and Kirschner to evaluate the
leading Regge trajectories \alpha(t) with the quantum numbers of nonexotic
quark-antiquark mesons at N_c = infinity and in the limit of t going to minus
infinity. In this region renormalization group improved perturbation theory
should be valid. We discuss the compatibility of nonlinear trajectories with
narrow resonance approximations.


title:
Grand Unification, Gravitational Waves, and the Cosmic Microwave
  Background Anisotropy

abstract:
  We re-examine the gravitational wave background resulting from inflation and
its effect on the cosmic microwave background radiation. The new COBE
measurement of a cosmic background quadrupole anisotropy places an upper limit
on the vacuum energy during inflation of $\approx 5 \times 10^{16}$ GeV. A
stochastic background of gravitational waves from inflation could produce the
entire observed signal (consistent with the observed dipole anisotropy and a
flat spectrum) if the vacuum energy during inflation was as small as $1.5
\times 10^{16}$ GeV at the 95\% confidence level. This coincides nicely with
the mass scale for Grand Unification inferred from precision measurements of
the electroweak and strong coupling constants, for the SUSY Grand Unified
Theories. Thus COBE could be providing the first direct evidence, via
gravitational waves, for GUTs, and supersymmetry. Further tests of this
possibility are examined, based on analyzing the energy density associated with
gravitational waves from inflation.


title:
Large-order perturbation theory for the electromagnetic current-current
  correlation function

abstract:
  The constraints imposed by asymptotic freedom and analyticity on the
large-order behavior of perturbation theory for the electromagnetic
current-current correlation function are examined. By suitably applying the
renormalization group, the coefficients of the asymptotic expansion in the deep
Euclidean region may be expressed explicitly in terms of the perturbative
coefficients of the Minkowski space discontinuity (the $R$-ratio in $e^+ e^-$
scattering). This relation yields a ``generic'' prediction for the large-order
behavior of the Euclidean perturbation series and suggests the presence of
non-perturbative $1/q^2$ correction in the Euclidian correlation function. No
such ``generic'' prediction can be made for the physically measurable
$R$-ratio. A novel functional method is developed to obtain these results.


title: Oscillations of Pseudo-Dirac Neutrinos and the Solar Neutrino Problem

abstract:
  The oscillations of pseudo-Dirac neutrinos in matter are discussed and
applied to the solar neutrino problem. Several scenarios such as both $\nu_e$
and $\nu_{\mu}$ being pseudo-Dirac and only $\nu_e$ or $\nu_{\mu}$ being
pseudo-Dirac are examined. It is shown that the allowed region in the
mass-mixing angle parameter space obtained by comparing the solar neutrino data
with the calculations based on the standard solar model and the MSW effect is
not unique. The results depend on the nature of neutrinos; for example, if both
$\nu_e$ and $\nu_{\mu}$ are pseudo-Dirac, the allowed region determined by the
current solar neutrino data does not overlap with that obtained in the usual
case of pure Dirac or Majorana neutrinos.


title:
4-dimensional spontaneously broken U(1)L gauge theories without
  asymptotic quarks and Higgs boson

abstract:
  We show, in the case of a U(1)L spontaneously broken gauge theory, how
introducing a composite Wess-Zumino field, with a derivative coupling to the
fermionic current, and a composite scalar sector leads to infinitely massive
quarks and Higgs boson, making them unobservable as asymptotic states. This
results from the constraints that need to be introduced in the Feynman path
integral to take into account the non-independent scalar degrees of freedom,
and from the breaking of the symmetry by the non-vanishing vacuum expectation
value of the Higgs boson. Unitarity and gauge invariance are achieved; the
former can be made explicit by "gauging" the Wess-Zumino field into the third
component of the massive gauge boson; the latter is recovered at the level of
Green functions through the cancellation of the non-invariance of the action
with that of the fermionic measure. The compensation of the anomaly can also be
seen as a consequence of the infinite mass of the fermions. The pseudoscalar
partner of the Higgs is shown to behave like an abelian pion, specially as far
are its leptonic decays are concerned; in particular, no extra scale of
interaction is needed, unlike in "technicolour" theories. The correct decay of
the pion into two photons is recovered despite the abscence of anomaly.
Arguments are given in favour of renormalizability. The leptonic sector is the
object of a subsequent work.


title: Dark Matter with Variable Masses

abstract:
  String effective theories contain a dilaton scalar field which couples to
gravity, matter and radiation. In general, particle masses will have different
dilaton couplings. We can always choose a conformal frame in which baryons have
constant masses while (non--baryonic) dark matter have variable masses, in the
context of a scalar--tensor gravity theory. We are interested in the
phenomenology of this scenario. Dark matter with variable masses could have a
measurable effect on the dynamical motion of the halo of spiral galaxies, which
may affect cold dark matter models of galaxy formation. As a consequence of
variable masses, the energy--momentum tensor is not conserved; there is a
dissipative effect, due to the dilaton coupling, associated with a ``dark
entropy" production. In particular, if axions had variable masses they could be
diluted away, thus opening the ``axion window". Assuming that dark matter with
variable masses dominates the cosmological evolution during the matter era, it
will affect the primordial nucleosynthesis predictions on the abundances of
light elements. Furthermore, the dilaton also couples to radiation in the form
of a variable gauge coupling. Experimental bounds will constrain the parameters
of this model.


title: Screening of Very Intense Magnetic Fields by Chiral Symmetry Breaking

abstract:
  In very intense magnetic fields, $B > 1.5\times 10^{14}$ T, the breaking of
the strong interaction $SU(2)\times SU(2)$ symmetry arranges itself so that
instead of the neutral $\sigma$ field acquiring a vacuum expectation value it
is the charged $\pi$ field that does and the magnetic field is screened.
Details are presented for a magnetic field generated by a current in a wire; we
show that the magnetic field is screened out to a distance $\rho_o\sim I/f_\pi
m_\pi$ from the wire.


title: New Probes for Extended Gauge Structures at HERA

abstract:
  Doncheski and Hewett have recently shown that the ratio of neutral current to
charged current cross sections, $R={\sigma_{NC}}/{\sigma_{CC}}$, can provide a
more sensitive probe for the existence of heavy leptoquarks at HERA than the
usual proceedure which makes use of neutral current asymmetries. The apparent
reason for this is that the Standard Model expectations for {\it both} of these
cross sections are modified by the existence of such particles in a
semi-coherent manner. In this paper we apply this technique to extended
electroweak models whose spectrum contains both a $W'$ and a $Z'$. We find that
measurements of $R$ can, for some models, substantially increase the HERA
search range for new gauge bosons beyond that which can be probed using the
more conventional asymmetries.


title: A General Lower Bound for Radiative B Decay

abstract:
  In a wide class of models -- including the standard model -- flavor-changing
neutral currents are suppressed by an approximate chiral symmetry of the
low-energy lagrangian. This symmetry allows the derivation of general relations
among low-energy flavour-changing processes. We derive one such: the relative
sizes of the decay rates b --> s gamma, b --> d gamma and s --> d gamma.
Together with a unitarity-related lower bound on the rate for the
strangeness-changing hyperon decay Omega^- --> Xi^- \gamma we obtain a
reasonably model-independent lower bound for the inclusive b --> s gamma rate.


title: Fast Neutrino Decay in the Minimal Seesaw Model

abstract:
  Neutrino decay in the minimal seesaw model containing three right handed
neutrinos and a complex $SU(2)\times U(1)$ singlet Higgs in addition to the
standard model fields is considered. A global horizontal symmetry $U(1)_H$ is
imposed, which on spontaneous breaking gives rise to a Goldstone boson. This
symmetry is chosen in a way that makes a) the contribution of heavy ($\leq$
  MeV) majorana neutrinos to the neutrinoless double beta decay amplitude
vanish and b) allows the heavy neutrino to decay to a lighter neutrino and the
Goldstone boson. It is shown that this decay can occur at a rate much faster
than in the original Majoron model even if one does not introduce any
additional Higgs fields as is done in the literature. Possibility of describing
the 17 keV neutrino in this minimal seesaw model is investigated. While most of
the cosmological and astrophysical constraints on the 17 keV neutrino can be
satisfied in this model, the laboratory limits coming from the neutrino
oscillations cannot be easily met. An extension which removes this inadequacy
and offers a consistent description of the 17 keV neutrino is discussed.


title: Nonfactorizable Amplitudes in Weak Nonleptonic Decays of Heavy Mesons

abstract:
  We discuss nonfactorizable $1/N_c$ contributions in the amplitudes of
non-leptonic exclusive decays of the type $B\rightarrow D\pi$ ($N_c$ is the
number of colors). In a certain kinematical limit rather reliable estimates are
possible. It is demonstrated that the nonfactorizable parts are of the same
order as the factorizable $1/N_c$ parts of the ampiltudes, and have the
opposite sign. Thus, an approximate rule of discarding $1/N_c$ corrections in
the nonleptonic exclusive decays emerges dynamically. It is shown that this
rule is not exact and the degree of compensation is different in different
channels.
  Our predictions make use of the fact that a key matrix element that measures
deviations from factorization can be determined using the heavy quark effective
theory.


title:
Constraints on Mirror Fermion Mixing Angles from Anomalous Magnetic
  Moment Data

abstract:
  The new contributions to the electron (muon) anomalous magnetic moment
arising in mirror fermion theories have been calculated. Imposing the
experimental constraint lowers the current upper bound on the ordinary - mirror
lepton mixing angles by a factor of 50 making predictions for mirror lepton
production at HERA undetectably small. A way out is to allow for different
mixing angles of the L and R field components. Choosing very small right mixing
angles compatibility with the anomalous magnetic moment measurement may be
easily maintained, while choosing left mixing angles close to the upper limits
yields still reasonable HERA cross-sections.


title: $\theta$ Bag and Quark Confinement

abstract:
  We propose $\theta$ bag through the wall separating $\theta=0$ and
$\theta=\pi$. $\theta$ may or may not be a dynamical field generating the wall.
For a massive pseudo scalar $\theta$, we present a two Higgs doublet model. We
also presnt an idea for quark confinement within this $\theta$ bag scheme.


title: Axions with Variable Masses

abstract:
  Axions with variable masses, in the context of a scalar--tensor gravity
theory, give a large entropy production during the matter era. The subsequent
axion dilution is proportional to their present energy density. Depending on
the parameters ($\beta_I,\beta_V$) of the model, this dilution relaxes or even
eludes the cosmological bound on the axion mass, therefore opening the
so--called ``axion window".


title: Strong CP-Problem in Superstring Theory

abstract:
  We apply the solution for the strong CP-problem in the 4-dimensional
superstring theory recently proposed by Ib${\rm\acute{a}\tilde{n}}$ez and
L${\rm\ddot{u}}$st to Calabi-Yau type models and study its phenomenological
aspects. In Calabi-Yau type models there seem to be phenomenologically
difficult problems in the axion decoupling from the neutral gauge currents and
the compatibility between the proton stability and the cosmological bound on
the axion. DFSZ type invisible axion mechanism which works without heavy extra
colored fields may be more promising than KSVZ axion in the viewpoint of proton
stability.


title: Recent Developments in Superstring Phenomenology

abstract:
  Recent developments in superstring phenomenology are summarized on a
non-technical level. (Talk presented at the XXVIIth Rencontre de Moriond on
Electroweak Interactions and Unified Theories.)


title: Supersymmetry, Naturalness, and Dynamical Supersymmetry Breaking

abstract:
  Models with dynamical supersymmetry breaking have the potential to solve many
of the naturalness problems of hidden sector supergravity models. We review the
argument that in a generic supergravity theory in which supersymmetry is {\it
dynamically} broken in the hidden sector, only tiny Majorana masses for
gauginos are generated. This situation is similar to that of theories with
continuous R-symmetries, for which Hall and Randall have suggested that gluino
masses could arise through mixings with an octet of chiral fields. We note that
in hidden sector models, such mixing can only occur if the auxiliary D field of
a $U(1)$ gauge field has an expectation value. This in turn gives rise to a
catastrophically large Fayet-Iliopoulos term for ordinary hypercharge. To solve
this problem it is necessary to unify hypercharge at least partially in a
non-Abelian group. We consider, also, some general issues in models with
continuous or discrete R symmetries, noting that it may be necessary to include
$SU(2)$ triplet fields, and that these are subject to various constraints. In
the course of these discussions, we consider a number of naturalness problems.
We suggest that the so-called ``$\mu$-problem" is not a problem, and point out
that in models in which the axion decay constant is directly related to the
SUSY breaking scale, squarks, sleptons and Higgs particles generically acquire
huge masses.


title:
Reparameterisation Invariance Constraints on Heavy Particle Effective
  Field Theories

abstract:
  Since fields in the heavy quark effective theory are described by both a
velocity and a residual momentum, there is redundancy in the theory: small
shifts in velocity may be absorbed into a redefinition of the residual
momentum. We demonstrate that this trivial reparameterisation invariance has
non-trivial consequences: it relates coefficients of terms of different orders
in the $1/m$ expansion and requires linear combinations of these operators to
be multiplicatively renormalised. For example, the operator $-D^2/2m$ in the
effective lagrangian has zero anomalous dimension, coefficient one, and does
not receive any non-perturbative contributions from matching conditions. We
also demonstrate that this invariance severely restricts the forms of operators
which may appear in chiral lagrangians for heavy particles.


title: Axino Mass

abstract:
  The mass of the axino is computed in realistic supersymmetric extensions of
the standard model. It is found to be strongly model dependent and can be as
small as a few keV but also as large as the gravitino mass. Estimates of this
mass can only be believed once a careful analysis of the scalar potential has
been performed.


title: Planck-Scale Physics and Neutrino Masses

abstract:
  We discuss gravitationally induced masses and mass splittings of Majorana,
Zeldovich-Konopinski-Mahmoud and Dirac neutrinos. Among other implications,
these effects can provide a solution of the solar neutrino puzzle. In
particular, we show how this may work in the 17 keV neutrino picture.


title: Z(N) interface tension in a hot SU(N) gauge theory

abstract:
  The interface tension between Z(N) vacua in a hot SU(N) gauge theory (without
dynamical fermions) is computed at next to leading order in weak coupling. The
Z(N) interface tension is related to the instanton of an effective action,
which includes both classical and quantum terms; a general technique for
treating consistently the saddle points of such effective actions is developed.
Loop integrals which arise in the calculation are evaluated by means of zeta
function techniques. As a byproduct, up to two loop order we find that the
stable vacuum is always equivalent to the trivial one, and so respects charge
conjugation symmetry.


title: Finite Temperature Scalar Potential from a 1/N Expansion

abstract:
  We compute the leading and next--to--leading corrections to the finite
temperature scalar potential for a 3+1 dimensional $\phi^4$ theory using a
systematic $1/N$ expansion. Our approach automatically avoids problems
associated with infrared divergences in ordinary perturbation theory in
$\hbar$. The leading order result does not admit a first order phase
transition. The subleading result shows that the exact theory can admit at best
only a very weak first order phase transition. For $N=4$ and weak scalar
coupling we find that $T_1$, the temperature at which tunneling from the origin
may begin in the case of a first order transition, must be less than about 0.5
percent larger than $T_2$, the temperature at which the origin changes from
being a local minimum to being a local maximum. We compare our results to the
effective potential found from a sum of daisy graphs.


title:
Bounds on Microscopic Physics from P and T Violation in Atoms and
  Molecules

abstract:
  Atomic and molecular electric dipole moments are calculated within the
minimal supersymmetric standard model. Present experiments already provide
strong bounds on the combination of phases responsible for the dipole moments
of the neutron and closed shell atoms. For a supersymmetry breaking scale of
100 GeV, these phases must be smaller than $ \sim 10^{-2}$.


title: Computing the Weak Mixing Angle from Anomaly Cancellation

abstract:
  I remark that the weak mixing angle in the standard model may be computed
even in the absence of a grand unification symmetry. In particular, if there is
an additional gauged $U(1)$ symmetry at some large scale which can be made
anomaly-free only by a Green-Schwarz (GS) mechanism, this typically results in
a prediction for the weak angle. In the case of the standard model one can see
that the standard Peccei-Quinn symmetry may be gauged and the anomalies
cancelled through a GS mechanism. Remarkably enough, cancelation of anomalies
works only for the `canonical' value $sin^2\theta _W=3/8$. In the case of the
supersymmetric standard model one can also find $U(1)$ currents which may be
made anomaly-free through a GS but the canonical value is only obtained in the
absence of any Higgs multiplet. If the analysis is extended to include $U(1)$
R-symmetries, there is a unique class of $U(1)$s which give rise to the
canonical value. The R-symmetry is only anomaly-free for $sin^2\theta
_W=(4N_g-3)/(10N_g-3N_D-3)$, where $N_g,N_D$ are the number of generations and
Higgs pairs. The natural context in which the above scenario may naturally
arise is string theory. I also emphasize other interesting possibilities
offered by the GS mechanism to model-building.


title: Covariant gauges at finite temperature

abstract:
  A prescription is presented for real-time finite-temperature perturbation
theory in covariant gauges, in which only the two physical degrees of freedom
of the gauge-field propagator acquire thermal parts. The propagators for the
unphysical degrees of freedom of the gauge field, and for the Faddeev-Popov
ghost field, are independent of temperature. This prescription is applied to
the calculation of the one-loop gluon self-energy and the two-loop interaction
pressure, and is found to be simpler to use than the conventional one.


title: Dispersion Relations in Quantum Chromodynamics

abstract:
  Dispersion relations for the scattering of hadrons are considered within the
framework of Quantum Chromodynamics. It is argued that the original methods of
proof remain applicable. The setting and the spectral conditions are provided
by an appropriate use of the BRST cohomology. Confinement arguments are used in
order to exclude quarks and gluons from the physical subspace. Local,
BRST-invariant hadron fields are considered as leading terms in operator
product expansions for products of fundamental fields. The hadronic amplitudes
have neither ordinary nor anomalous thresholds which are directly associated
with the underlying quark-gluon-structure. Proofs involving the Edge of the
Wedge Theorem and analytic completion are discussed briefly.


title: Best Fit to the Gluino Mass

abstract:
  Assuming that perturbative QCD is the dominant explanation for the narrowness
of the vector quarkonia, we perform a $\chi^2$ minimization analysis of their
hadronic decays as a function of two parameters, the mass of the gluino and the
value of ${\alpha}_3(M_Z)$. A value below 1 GeV for the gluino mass is strongly
preferred. Consequences for SUSY breaking scenarios are discussed.


title: Radiative Correction Effects of a Very Heavy Top

abstract:
  If the top is very heavy, m_t >> M_Z, the dominant radiative correction
effects in all electroweak precision tests can be exactly characterized in
terms of two quantities, the rho-parameter and the GIM violating Z -> b bbar
coupling. These quantities can be computed using the Standard Model Lagrangian
with vanishing gauge couplings. This is done here up to two loops for arbitrary
values of the Higgs mass.


title: Anomalous Radiative Decay of Heavy Higgs Boson

abstract:
  The radiative decay width of a heavy Higgs boson $H \rightarrow W^+W^-\gamma$
for a {\it hard} photon is calculated in the Standard Model and its extension
with anomalous $\gamma WW$ couplings. Its dependence on the Higgs mass, the two
unknown anomalous couplings, and the photon energy cutoff are studied in
detail. We show that this radiative decay of a heavy Higgs is not very
sensitive to a wide range of the anomalous couplings compared to the Standard
Model result.


title: Predictions for neutral K and B meson physics

abstract:
  Using supersymmetric grand unified theories, we have recently invented a
framework which allows the prediction of three quark masses, two of the
parameters of the Kobayashi-Maskawa matrix and tan $\beta$, the ratio of the
two vevs. These predictions are used to calculate $\epsilon$ and $\epsilon'$ in
the kaon system, B meson mass mixing and the size of CP asymmetries in the
decays of neutral B mesons to explicit final states of given CP.


title: Nonleptonic decays of K mesons revisited

abstract:
  We estimate nonfactorizable 1/$N_c$ contributions in the $K\rightarrow 2\pi$
amplitudes using the approach proposed in our previous work. It is demonstrated
that for the conventional (nonpenguin) operators these contributions are close
in magnitude to factorizable $1/N_c$ parts and have the opposite sign. Thus, an
approximate rule of discarding $1/N_c$ corrections in $K\rightarrow 2\pi$
decays is theoretically confirmed. As a result we find an extra suppression of
the matrix element of $O_4$ ($\Delta I=3/2$) and an extra enhancement of the
matrix element of $O_1$ ($\Delta I=1/2$).
  The parameter $B$ describing $K^0-\bar K^0$ mixing is also discussed.


title: Running Nonlocal Lagrangians

abstract:
  We investigate the renormalization of ``nonlocal'' interactions in an
effective field theory using dimensional regularization with minimal
subtraction. In a scalar field theory, we write an integro-differential
renormalization group equation for every possible class of graph at one loop
order.


title: Baryons Containing a Heavy Quark as Solitons

abstract:
  The possibility of interpreting baryons containing a single heavy quark as
bound states of solitons (that arise in the nonlinear sigma model) and heavy
mesons is explored. Particular attention is paid to the parity of the bound
states and to the role of heavy quark symmetry.


title:
Resonant Spin-Flavor Precession of Neutrinos As a Possible Solution to
  the Solar Neutrino Problem

abstract:
  Recent developments of the resonant neutrino spin-flavor precession scenario
and its applications to the solar neutrino problem are reviewed. We discuss in
particular the possibilities of reconciliation of strong time variations of the
solar neutrino flux observed in the Homestake ${}^{37}\$Cl experiment with
little or no time variation seen in the Kamiokande II experiment.


title: QCD Corrections to the Charged-Higgs-Boson Decay of a Heavy Top Quark

abstract:
  It is shown that up to an over all scale the lowest-order QCD corrections to
$t\to H^+b$ and to $t\to W^+b$ are the same in the heavy top limit.
Asymptotically, they are given by $-{4\alpha_s\over 3\pi}[{\pi^2\over
3}-{5\over 4}]$, resulting in a reduction in the decay rate by about $9\%$,
rather than $6\%$ reported previously in the literature. This is verified
explicitly by an analytic calculation. The application of the equivalence
theorem to this process is also discussed.


title: On Observing Top Quark Production at the Tevatron

abstract:
  A technique for separating top quark production from Standard Model
background events is introduced. It is applicable to the channel in which one
top quark decays semi-leptonically and its anti-quark decays hadronically into
three jets, or vice versa. The method is shown to discriminate dramatically
between Monte Carlo generated events with and without simulated top quarks of
mass around 120 GeV and above. The simulations were performed with CDF detector
characteristics incorporated, showing that the method is applicable to existing
data.


title: Higgs sector CP violation in the Minimal Supersymmetric Model

abstract:
  We study the possibility that CP is spontaneously broken in the Minimal
Supersymmetric Model when radiative corrections to the Higgs potential are
included. We show that this can only occur if a light Higgs boson exists.
Considering the recent ALEPH Higgs search, we exclude most of the parameter
space of the model. The possibility of explicit CP violation in the model is
also briefly discussed.


title: Baryogenesis from Unstable Domain Walls

abstract:
  There exists a class of cosmic strings that turn matter into antimatter
(Alice strings). In a GUT where the unbroken gauge group contains charge
conjugation ($C$), such strings form when a phase transition renders $C$ a
discrete symmetry. They become boundaries of domain walls at a later,
$C$-breaking transition. These `Alice walls' are cosmologically harmless, but
can play an important role in baryogenesis. We present a three-generation toy
model with scalar baryons, where a quasi-static Alice wall (or a gas of such
walls) temporarily gives rise to net baryogenesis of uniform sign everywhere in
space. This becomes a permanent baryon excess if the wall shrinks away early
enough.
  We comment on the possible relevance of a similar mechanism to baryogenesis
in a realistic $\soten$ unification model, where
  Alice walls would form at the scale of left-right symmetry breaking.


title: Heavy Axions From Strong Broken Horizontal Gauge Symmetry

abstract:
  We study the consequences of the existence and breaking of a Peccei--Quinn
symmetry within the context of a dynamical model of electroweak symmetry
breaking based on broken gauged flavour symmetries. We perform an estimate of
the axion mass by including flavour instanton effects and show that, for low
cut--offs, the axion is sufficiently massive to prevent it from being
phenomenologically unacceptable. We conclude with an examination of the strong
CP problem and show that our axion cannot solve the problem, though we indicate
ways in which the model can be extended so that the strong CP problem is
solved.


title:
Constraints From Gauge Coupling Unification On The Scale Of
  Supersymmetry Breaking

abstract:
  We reanalyze precision LEP data and coupling constant unification in the
minimal supersymmetric $SU(5)$ model including the evolution of the gaugino
masses. We derive general bounds on the primordial gaugino
supersymmetry-breaking mass-scale $m_{1/2}$ in terms of the various input
parameters. The model cannot accommodate $m_{1/2}<1\TeV$ for values of $\as <
0.115$, even for extreme $1-\sigma$ values of the other inputs. We emphasize
the sensitivity of this type of calculations to the various input parameters.


title:
Interpretation of Precision Measurements in the Strongly Interacting
  Limit of the Standard Electroweak Model

abstract:
  Strong rescattering corrections to one-loop contributions to the parameters
of the standard electroweak model are considered.


title: Flavor changing interactions mediated by scalars at the weak scale

abstract:
  The quark and lepton mass matrices possess approximate flavor symmetries.
Several results follow if the interactions of new scalars possess these
approximate symmetries. Present experimental bounds allow these exotic scalars
to have a weak scale mass. The Glashow-Weinberg criterion is rendered
unnecessary. Finally, rare leptonic B meson decays provide powerful probes of
these scalars, especially if they are leptoquarks.


title: Analysis of Running Coupling Constant Unification in String Theory

abstract:
  We use recently obtained 2-loop string coupling constants to analyze a class
of string models based on orbifold compactification. Assuming weak coupling at
the string scale and single-scale unification leads to restrictions on the
spectrum of massive (between the string scale and the weak scale) matter
supermultiplets and/or on the Kac-Moody algebra level.


Reply to Comments on ``Asymptotic Estimate of the {\it n}-Loop QCD
  Contribution to the Total $e^{+}e^{-}$ Annihilation Cross Section''


title: Can HERA See an $e u --> e c$ Signal of a Virtual Leptoquark?

abstract:
  Virtual leptoquarks could be detected at HERA through some nonstandard
effects. Here we explore the possibility that virtual leptoquarks could be
discovered via $e u --> e c$ scattering, assuming integrated luminosity of 200
pb$^{-1}$ and charm identification efficiency of 1%. We study the implications
of low energy data for the leptoquarks couplings and find that the most
relevant bound for the HERA cross sections comes from inclusive $c -->
e^+e^-~+~any$. This bound implies that the $e u --> e c$ cross sections for
virtual leptoquarks are just too small for observation of the signal. With an
improvement by a factor of ~2 on the luminosity or on charm identification it
could be possible to see virtual leptoquarks with {\it maximum couplings} up to
~1.5 - 2 TeV. However, the prospects for discovering the virtual particles if
their couplings are somewhat below present bounds are very dim. We point out
that this cross section could be very large for leptoquarks lighter than HERA's
kinematical limit, and if such a leptoquark is discovered we recommend
searching for a possible $e u --> e c$ signal. Our results may also serve as an
update on the maximum cross sections for leptoquark mediated $e u --> \mu c$
scattering.


title:
Standard Model Contributions to the Neutrino Index of Refraction in the
  Early Universe

abstract:
  With the standard electroweak interactions, the lowest-order coherent forward
scattering amplitudes of neutrinos in a CP symmetric medium (such as the early
universe) are zero, and the index of refraction of a propagating neutrino can
only arise from the expansion of gauge boson propagators, from radiative
corrections, and from new physics interactions. Motivated by nucleosynthesis
constraints on a possible sterile neutrino (suggested by the solar neutrino
deficit and a possible $17\ keV$ neutrino), we calculate the standard model
contributions to the neutrino index of refraction in the early universe,
focusing on the period when the temperature was of the order of a few $MeV$. We
find sizable radiative corrections to the tree level result obtained by the
expansion of the gauge boson propagator. For $\nu_e+e(\bar{e})\to
\nu_e+e(\bar{e})$ the leading log correction is about $+10\%$, while for
$\nu_e+\nu_e(\bar{\nu}_e)\to \nu_e+\nu_e(\bar{\nu}_e)$ the correction is about
$+20\%$. Depending on the family mixing (if any), effects from different family
scattering can be dominated by radiative corrections. The result for
$\nu+\gamma\to\nu+\gamma$ is zero at one-loop level, even if neutrinos are
massive. The cancellation of infrared divergence in a coherent process is also
discussed.


title: Discrete Symmetry, Neutrino Magnetic Moment and the 17 Kev Neutrino

abstract:
  The problem of generating large transition magnetic moments for nearly
massless neutrinos in a truly three--generation case is discussed. A model to
achieve the same by exploiting an octahedral symmetry is presented. The scheme
also accomodates a radiatively generated mass of $17\:keV$ for a pseudo--Dirac
neutrino that decays rapidly through the Majoron channel.


title: Hadronic Instabilities in Very Intense Magnetic Fields

abstract:
  Composite hadronic states exhibit interesting properties in the presence of
very intense magnetic fields, such as those conjectured to exist in the
vicinity of certain astrophysical objects. We discuss three scenarios. (i) The
presence of vector particles with anomalous magnetic moment couplings to scalar
particles, induces an instability of the vacuum. (ii) A delicate interplay
between the anomalous magnetic moments of the proton and neutron makes, in
magnetic fields $B\ge 2\times 10^{14}$ T, the neutron stable and for fields
$B\ge 5\times 10^{14}$ T the proton becomes unstable to a decay into a neutron
via $\beta$ emission. (iii) In the unbroken chiral $\sigma$ model magnetic
fields would be screened out as in a superconductor. It is the explicit
breaking of chiral invariance that restores standard electrodynamics.
Astrophysical consequences of all these phenomena are discussed.


title:
Cosmic $\Delta B$ from Lepton Violating Interactions at the Electroweak
  Phase Transition

abstract:
  We propose a new mechanism for late cosmological baryon asymmetry in models
with first order electroweak phase transition. Lepton asymmetry arises through
the decay of particles produced out of equilbrium in bubble collisions and is
converted into baryon asymmetry by sphalerons. Supersymmetric models with
explicitly broken R-parity may provide a suiatble framework for the
implementation of this mechanism.


title: Exact Nonperturbative Unitary Amplitudes for 1->N Transitions

abstract:
  I present an extension to arbitrary N of a previously proposed field
theoretic model, in which unitary amplitudes for $1->8$ processes were
obtained. The Born amplitude in this extension has the behavior
$A(1->N)^{tree}\ =\ g^{N-1}\ N!$ expected in a bosonic field theory. Unitarity
is violated when $|A(1->N)|>1$, or when $N>\N_crit\simeq e/g.$ Numerical
solutions of the coupled Schr\"odinger equations shows that for weak coupling
and a large range of $N>\ncrit,$ the exact unitary amplitude is reasonably fit
by a factorized expression $|A(1->N)| \sim (0.73 /N) \cdot \exp{(-0.025/\g2)}$.
The very small size of the coefficient $1/\g2$ , indicative of a very weak
exponential suppression, is not in accord with standard discussions based on
saddle point analysis, which give a coefficient $\sim 1.\ $ The weak dependence
on $N$ could have experimental implications in theories where the exponential
suppression is weak (as in this model). Non-perturbative contributions to
few-point correlation functions in this theory would arise at order $K\ \simeq\
\left((0.05/\g2)+ 2\ ln{N}\right)/ \ ln{(1/\g2)}$ in an expansion in powers of
$\g2.$


title: Debye Screening and Baryogenesis during the Electroweak Phase Transition

abstract:
  We examine a recent claim that Debye screening will affect the charge
transport mechanism of anomalous electroweak baryogenesis. We show that the
effects of gauge charge screening do not affect the baryon number produced
during a first order electroweak phase transition. (Requires harvmac.tex)


title: Neutrino Magnetic Moment Model and Solar Neutrino Problem

abstract:
  We examine the time variation problem of solar neutrinos in the spin-flavour
precession mechanism taking into account the $\nu_e$-$\nu_{\mu}$ mixing. The
models with the small and large mixing angle are studied. It shows that the
models which realize $m_{\nu_e\nu_e} \sim m_{\nu_{\mu}\nu_{\mu}} \ll
m_{\nu_e\nu_{\mu}}$ and $m_{\nu_e\nu_e} \sim m_{\nu_{\mu}\nu_{\mu}} {^>_\sim}
m_{\nu_e\nu_{\mu}}$ seem to have preferable time variation features. It is very
interesting that the former type of models can give the large magnetic moment
to neutrinos and also suppress the radiative mass correction naturally.


title: Semilocal Defects

abstract:
  I analyze the interplay of gauge and global symmetries in the theory of
topological defects. In a two-dimensional model in which both gauge symmetries
and {\it exact} global symmetries are spontaneously broken, stable vortices may
fail to exist even though magnetic flux is topologically conserved. Following
Vachaspati and Ach\'ucarro, I formulate the condition that must be satisfied by
the pattern of symmetry breakdown for finite-energy configurations to exist in
which the conserved magnetic flux is spread out instead of confined to a
localized vortex. If this condition is met, vortices are always unstable at
sufficiently weak gauge coupling. I also describe the properties of defects in
models with an ``accidental'' symmetry that is partially broken by gauge boson
exchange. In some cases, the spontaneously broken accidental symmetry is not
restored inside the core of the defect. Then the structure of the defect can be
analyzed using an effective field theory; the details of the physics
responsible for the spontaneous symmetry breakdown need not be considered.
Examples include ``semilocal'' domain walls and vortices that are classically
unstable, but are stabilized by loop corrections, and ``semilocal'' magnetic
monopoles that have an unusual core structure. Finally, I examine the general
theory of the ``electroweak strings'' that were recently discussed by
Vachaspati. These arise only in models with gauge boson ``mixing,'' and can
always end on magnetic monopoles. Cosmological implications are briefly
discussed.


title: Effective Heavy Quark Theory

abstract:
  We show how heavy quark effective theory, including 1/M corrections, may be
matched onto dynamical quark models by making a specific choice of K,m and v in
the p=mv+K expansion. We note that Wigner rotations of heavy quark spins arise
at $O(p^2/m^2)$ in non-relativistic models but at $O(\Lambda_{QCD}/M_Q)$ or
O(velocity-transfer) in HQET and so are necessary for a consistent treatment.


title:
Aspects of Radiative Electroweak Symmetry Breaking in Supergravity
  Models

abstract:
  We discuss several aspects of state-of-the-art calculations of radiative
electroweak symmetry breaking in supergravity models. These models have a
five-dimensional parameter space in contrast with the 21-dimensional one of the
MSSM. We examine the Higgs one-loop effective potential $V_1=V_0+\Delta V$, in
particular how its renormalization-scale ($Q$) independence is affected by the
approximations used to calculate $\Delta V$ and by the presence of a
Higgs-field-independent term which makes $V_1(0)\not=0$. We show that the
latter must be subtracted out to achieve $Q$-independence. We also discuss our
own approach to the exploration of the five-dimensional parameter space and the
fine-tuning constraints within this approach. We apply our methods to the
determination of the allowed region in parameter space of two models which we
argue to be the prototypes for conventional (SSM) and string (SISM) unified
models. To this end we impose the electroweak breaking constraint by minimizing
the one-loop effective potential and study the shifts in $\mu$ and $B$ relative
to the values obtained using the tree-level potential. These shifts are most
significant for small values of $\mu$ and $B$, and induce corresponding shifts
on the lightest $\mu$- and/or $B$-dependent particle masses, \ie, those of the
lightest stau, neutralino, chargino, and Higgs boson states. Finally, we
discuss the predictions for the squark, slepton, and one-loop corrected Higgs
boson masses.


title: Z' Decays into Four Fermions

abstract:
  If a new $Z'$ is discovered with a mass $\sim 1 \ TeV$ at LHC/SSC, its (rare)
decays into two charged leptons plus missing transverse energy will probe the
$Z'$ coupling to the lepton doublet $(\nu,e)_L$ and to $W^+W^-$, allowing
further discrimination among extended electroweak models.


title: Electroweak Baryogenesis: An Overview (Where are We Now?)

abstract:
  It now seems plausible that the observed baryon asymmetry may have been
produced at the electroweak phase transition. We review the considerations
which lead to this conclusion, focusing on the obstacles to making reliable
estimates. These arise from incomplete knowledge of baryon-violating rates near
the phase transition, our limited understanding of the phase transition itself,
and incomplete understanding of the mechanisms which actually lead to an
asymmetry.


title: Probing New Gauge Boson Couplings via Three-Body Decays

abstract:
  We examine the possibility of using rare, 3-body decays of a new neutral
gauge boson, \ztwo, to probe its gauge couplings at hadron colliders.
Specifically, we study the decays $\ztwo\to W\ell\nu$ and $\ztwo\to
Z\nu\bar\nu$ and find that much knowledge of the \ztwo\ properties can be
obtained from these processes. In particular, these decay modes can yield
valuable information on the amount of $Z_1-Z_2$ mixing, on the generation
dependence of the \ztwo\ couplings, on the properties of the new generator
associated with the \ztwo, as well as being used to distinguish between
possible extended models. The analogous 3-body decays into a new, heavy charged
gauge boson, $\ztwo\to W_2^\pm\ell^\mp\nu$, are also investigated in models
where this can occur.


title:
Analyticity, Crossing Symmetry and the Limits of Chiral Perturbation
  Theory

abstract:
  The chiral Lagrangian for Goldstone boson scattering is a power series
expansion in numbers of derivatives. Each successive term is suppressed by
powers of a scale, $\Lambda_\chi$, which must be less than of order $4\pi
f/\sqrt{N}$ where $f$ is the Goldstone boson decay constant and $N$ is the
number of flavors. The chiral expansion therefore breaks down at or below $4
\pi f/\sqrt{N}$. We argue that the breakdown of the chiral expansion is
associated with the appearance of physical states other than Goldstone bosons.
Because of crossing symmetry, some ``isospin'' channels will deviate from their
low energy behavior well before they approach the scale at which their low
energy amplitudes would violate unitarity. We argue that the estimates of
``oblique'' corrections from technicolor obtained by scaling from QCD are
untrustworthy.


title:
Infrared Effects and Bubble Propagation at the Electroweak Phase
  Transition

abstract:
  We discuss aspects of poor infrared behaviour of the perturbation expansion
for the effective potential of the Higgs mode near the electroweak phase
transition, and enlarge on the discovery that higher order effects weaken the
transition. In addition, we outline our recent attempts at understanding the
dynamics involved in the propagation of bubbles formed in the first order
transition.