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This is a second paper describing the calculation of spectroscopy for
orbitally excited states from lattice simulations of Quantum Chromodynamics.
New features include higher statistics for P-wave systems and first results for
the spectroscopy of D-wave mesons and baryons, for relatively heavy quark
masses. We parameterize the Coulomb gauge wave functions for P-wave and D-wave
systems and compare them to those of their corresponding S-wave states.
|
hep-lat/9206011
| 727,353 |
A finite-dimensional su($N$) Lie algebra equation is discussed that in the
infinite $N$ limit (giving the area preserving diffeomorphism group) tends to
the two-dimensional, inviscid vorticity equation on the torus. The equation is
numerically integrated, for various values of $N$, and the time evolution of an
(interpolated) stream function is compared with that obtained from a simple
mode truncation of the continuum equation. The time averaged vorticity moments
and correlation functions are compared with canonical ensemble averages.
|
hep-th/9206025
| 727,354 |
We generalize to p-dimensional extended objects and type II superstrings a
recently proposed Green-Schwarz type I superstring action in which the tension
$T$ emerges as an integration constant of the equations of motion. The action
is spacetime scale-invariant but its equations of motion are equivalent to
those of the standard super p-brane for $T\ne 0$ and the null super p-brane for
$T=0$. We also show that for $p=1$ the action can be written in ``Born-Infeld''
form.
|
hep-th/9206026
| 727,354 |
Free planar electrons in a uniform magnetic field are shown to possess the
symmetry of area-preserving diffeomorphisms ($W$-infinity algebra).
Intuitively, this is a consequence of gauge invariance, which forces dynamics
to depend only on the flux. The infinity of generators of this symmetry act
within each Landau level, which is infinite-dimensional in the thermodynamical
limit. The incompressible ground states corresponding to completely filled
Landau levels (integer quantum Hall effect) are shown to be infinitely
symmetric, since they are annihilated by an infinite subset of generators. This
geometrical characterization of incompressibility also holds for fractional
fillings of the lowest level (simplest fractional Hall effect) in the presence
of Haldane's effective two-body interactions. Although these modify the
symmetry algebra, the corresponding incompressible ground states proposed by
Laughlin are again symmetric with respect to the modified infinite algebra.
|
hep-th/9206027
| 727,354 |
We are interested in the question when a Banach space $X$ with an
unconditional basis is isomorphic (as a Banach space) to an order-continuous
nonatomic Banach lattice. We show that this is the case if and only if $X$ is
isomorphic as a Banach space with $X(\ell_2)$. This and results of J. Bourgain
are used to show that spaces $H_1(\bold T^n)$ are not isomorphic to nonatomic
Banach lattices. We also show that tent spaces introduced in \cite{4} are
isomorphic to Rad $H_1$.
|
math/9206202
| 727,354 |
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.
|
hep-ph/9206212
| 727,354 |
We investigate the crumpling transition for a dynamically triangulated random
surface embedded in two dimensions using an effective model in which the
disordering effect of the $X$ variables on the correlations of the normals is
replaced by a long-range ``antiferromagnetic'' term. We compare the results
from a Monte Carlo simulation with those obtained for the standard action which
retains the $X$'s and discuss the nature of the phase transition.
|
hep-lat/9206012
| 727,357 |
A closed and explicit formula for all $\su{(3)}_k$ fusion coefficients is
presented which, in the limit $k \rightarrow \infty$, turns into a simple and
compact expression for the $su(3)$ tensor product coefficients. The derivation
is based on a new diagrammatic method which gives directly both tensor product
and fusion coefficients.
|
hep-th/9206032
| 727,357 |
Many $W$-algebras (e.g. the $W_N$ algebras) are consistent for all values of
the central charge except for a discrete set of exceptional values. We show
that such algebras can be contracted to new consistent degenerate algebras at
these exceptional values of the central charge.
|
hep-th/9206031
| 727,357 |
We argue, that for a general class of nontrivial bosonic theories the path
integral can be related to an equivariant generalization of conventional
characteristic classes.
|
hep-th/9206033
| 727,357 |
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
$\g2.$
|
hep-ph/9206213
| 727,357 |
We propose a system of functional relations having a universal form connected
to the $U_q(X^{(1)}_r)$ Bethe ansatz equation. Based on the analysis of it, we
conjecture a new sum formula for the Rogers dilogarithm function in terms of
the scaling dimensions of the $X^{(1)}_r$ parafermion conformal field theory.
|
hep-th/9206034
| 727,358 |
Matrix models of 2D quantum gravity are either exactly solvable for matter of
central charge $ c\leq 1, $ or not understood. It would be useful to devise an
approximate scheme which would be reasonable for the known cases and could be
carried to the unsolved cases in order to achieve at least a qualitative
understanding of the properties of the models. The double scaling limit is an
indication that a change of the length scale induces a flow in the parameters
of the theory, the size of the matrix and the coupling constants for matrix
models, at constant long distances physics. We construct here these
renormalization group equations at lowest orders in various cases to check that
we reproduce qualitatively the properties of $ c\leq 1 $ models.
|
hep-th/9206035
| 727,358 |
Quantum field theory is discussed in M\"obius corner kaleidoscopes using the
method of images. The vacuum average of the stress-energy tensor of a free
field is derived and is shown to be a simple sum of straight cosmic string
expressions, the strings running along the edges of the corners. It does not
seem possible to set up a spin-half theory easily.
|
hep-th/9206036
| 727,358 |
Integrability of equations of topological-antitopological fusion (being
proposed by Cecotti and Vafa) describing ground state metric on given 2D
topological field theory (TFT) model, is proved. For massive TFT models these
equations are reduced to a universal form (being independent on the given TFT
model) by gauge transformations. For massive perturbations of topological
conformal field theory models the separatrix solutions of the equations bounded
at infinity are found by the isomonodromy deformations method. Also it is shown
that ground state metric together with some part of the underlined TFT
structure can be parametrized by pluriharmonic maps of the coupling space to
the symmetric space of real positive definite quadratic forms.
|
hep-th/9206037
| 727,358 |
We show that there is a very simple relationship between differential and
dimensional renormalization of low-order Feynman graphs in renormalizable
massless quantum field theories. The beauty of the differential approach is
that it achieves the same finite results as dimensional renormalization without
the need to modify the space time dimension.
|
hep-th/9206038
| 727,358 |
We study the nonrelativistic limit of the $N=2$ supersymmetric Chern-Simons
matter system. We show that in addition to Galilean invariance the model admits
a set of symmetries generated by fermionic charges, which can be interpreted as
an {\it extended Galilean supersymmetry }. The system also possesses a hidden
conformal invariance and then the full group of symmetries is the {\it extended
superconformal Galilean} group. We also show that imposing extended
superconformal Galilean symmetry determines the values of the coupling
constants in such a way that their values in the bosonic sector agree with the
values of Jackiw and Pi for which self-dual equation exist. We finally analyze
the second quantized version of the model and the two-particle sector.
|
hep-th/9206039
| 727,358 |
Classical $W$-algebras in higher dimensions are constructed. This is achieved
by generalizing the classical Gel'fand-Dickey brackets to the commutative limit
of the ring of classical pseudodifferential operators in arbitrary dimension.
These $W$-algebras are the Poisson structures associated with a higher
dimensional version of the Khokhlov-Zabolotskaya hierarchy (dispersionless
KP-hierarchy). The two dimensional case is worked out explicitly and it is
shown that the role of Diff$S(1)$ is taken by the algebra of generators of
local diffeomorphisms in two dimensions.
|
hep-th/9206040
| 727,358 |
S-matrices for integrable perturbations of $N=2$ superconformal field
theories are studied. The models we consider correspond to perturbations of the
coset theory $G_k \times H_{g-h} /H_{k+g-h} $. The perturbed models are closely
related to $\hat G$-affine Toda theories with a background charge tuned to $H$.
Using the quantum group restriction of the affine Toda theories we derive the
S-matrix.
|
hep-th/9206041
| 727,359 |
We study symmetries between untwisted and twisted strings on asymmetric
orbifolds. We present a list of asymmetric orbifold models to possess
intertwining currents which convert untwisted string states to twisted ones,
and vice versa. We also present a list of heterotic strings on asymmetric
orbifolds with supersymmetry between untwisted and twisted string states. Some
of properties inherent in asymmetric orbifolds, which are not shared by
symmetric orbifolds, are pointed out.
|
hep-th/9206042
| 727,359 |
A very general class of Lagrangians which couple scalar fields to gravitation
and matter in two spacetime dimensions is investigated. It is shown that a
vector field exists along whose flow lines the stress-energy tensor is
conserved, regardless of whether or not the equations of motion are satisfied
or if any Killing vectors exist. Conditions necessary for the existence of
Killing vectors are derived. A new set of 2D black hole solutions is obtained
for one particular member within this class of Lagrangians. One such solution
bears an interesting resemblance to the 2D string-theoretic black hole, yet
contains markedly different thermodynamic properties.
|
hep-th/9206044
| 727,359 |
Two-dimensional Maxwell-dilaton quantum gravity, which covers a large family
of the actions for two-dimensional gravity (in particular, string-inspired
models) is investigated. Charged black holes which appear in the theory are
briefly discussed. The one-loop divergences in the linear covariant gauges are
calculated. It is shown that for some choices of the dilaton potential and
dilaton-Maxwell coupling, the theory is one-loop multiplicatively
renormalizable (or even finite). A comparison with the divergences structure of
four-dimensional Einstein-Maxwell gravity is given.
|
hep-th/9206043
| 727,359 |
The 1/N expansion for the O(N) vector model in four dimensions is
reconsidered. It is emphasized that the effective potential for this model
becomes everywhere complex just at the critical point, which signals an
unstable vacuum. Thus a critical O(N) vector model cannot be consistently
defined in the 1/N expansion for four-dimensions, which makes the existence of
a double-scaling limit for this theory doubtful.
|
hep-th/9206045
| 727,359 |
We show that a class of models for particles with internal degrees of freedom
are integrable. These systems are basically generalizations of the models of
Calogero and Sutherland. The proofs of integrability are based on a recently
developed exchange operator formalism. We calculate the wave-functions for the
Calogero-like models and find the ground-state wave-function for a
Calogero-like model in a position dependent magnetic field. This last model
might have some relevance for matrix models of open strings.
|
hep-th/9206046
| 727,359 |
We show that the quantum-algebra-invariant open spin chains associated with
the affine Lie algebras $A^{(1)}_n$ for $n>1$ are integrable. The argument,
which applies to a large class of other quantum-algebra-invariant chains, does
not require that the corresponding $R$ matrix have crossing symmetry.
|
hep-th/9206047
| 727,359 |
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)
|
hep-ph/9206214
| 727,359 |
Using the conformal invariance of the $SL(2,R)\otimes SO(1,1)^{d-2}/SO(1,1)$
coset models we calculate the conformally exact metric and dilaton, to all
orders in the $1/k$ expansion. We consider both vector and axial gauging. We
find that these cosets represent two different space--time geometries: ($2d$
black hole)$\otimes \IR^{d-2}$ for the vector gauging and ($3d$ black
string)$\otimes \IR^{d-3}$ for the axial one. In particular for $d=3$ and for
the axial gauging one obtains the exact metric and dilaton of the charged black
string model introduced by Horne and Horowitz. If the value of $k$ is finite we
find two curvature singularities which degenerate to one in the semi--classical
$k\to \infty$ limit. We also calculate the reflection and transmission
coefficients for the scattering of a tachyon wave and using the Bogoliubov
transformation we find the Hawking temperature.
|
hep-th/9206048
| 727,359 |
A recent proposal by Kaplan for a chiral gauge theory on the lattice is
tested with background gauge fields. The spectrum of the finite lattice
Hamiltonian is calculated and the existence of a chiral fermion is
demonstrated. Lattice doublers are found to decouple. The flavor anomalies,
which are in agreement with the continuum anomaly relation, are obeserved on a
finite lattice. Non-trivial anomaly cancellation is observed in a chiral gauge
current.
|
hep-lat/9206014
| 727,359 |
A method for simulating chiral gauge theories on the lattice is proposed,
involving zeromodes on a topological defect. Lattice doublers may be decoupled
in a gauge invariant manner, and flavor anomalies can be directly observed on a
finite lattice. (Requires harvmac)
|
hep-lat/9206013
| 727,360 |
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.
|
hep-ph/9206215
| 727,360 |
We solve the N-body Calogero problem, \ie N particles in 1 dimension subject
to a two-body interaction of the form $\half \sum_{i,j}[ (x_i - x_j)^2 + g/
{(x_i - x_j)^2}]$, by constructing annihilation and creation operators of the
form $ a_i^\mp =\frac 1 {\sqrt 2} (x _i \pm i\hat{p}_i )$, where $\hat{p}_i$ is
a modified momentum operator obeying %!!!!!!! Heisenberg-type commutation
relations with $x_i$, involving explicitly permutation operators. On the other
hand, $ D_j =i\,\hat{p}_j$ can be interpreted as a covariant derivative
corresponding to a flat connection. The relation to fractional statistics in
1+1 dimensions and anyons in a strong magnetic field is briefly discussed.
|
hep-th/9206049
| 727,360 |
We apply the method of differential renormalization to two and three
dimensional abelian gauge theories. The method is especially well suited for
these theories as the problems of defining the antisymmetric tensor are avoided
and the calculus involved is impressively simple. The topological and dynamical
photon masses are obtained.
|
hep-th/9206050
| 727,360 |
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.
|
hep-ph/9206216
| 727,360 |
An O($\tilde{d}$, $\tilde{d}$) transformation is given which relates ungauged
string actions to the gauged ones for a large class of models discussed
recently by Giveon and Rocek. Interestingly, the transformation is background
independent and has a unique matrix representation in a given space-time
dimension.
|
hep-th/9206051
| 727,360 |
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.
|
hep-ph/9206217
| 727,360 |
We propose a class of purely elastic scattering theories generalising the
staircase model of Al. B. Zamolodchikov, based on the affine Toda field
theories for simply-laced Lie algebras g=A,D,E at suitable complex values of
their coupling constants. Considering their Thermodynamic Bethe Ansatz
equations, we give analytic arguments in support of a conjectured
renormalisation group flow visiting the neighbourhood of each W_g minimal model
in turn.
|
hep-th/9206052
| 727,360 |
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.
|
hep-ph/9206218
| 727,360 |
We perform Monte Carlo simulations using the Wolff cluster algorithm of the
XY model on both fixed and dynamical phi-cubed graphs (i.e. without and with
coupling to two-dimensional quantum gravity). We compare the numerical results
with the theoretical expectation that the phase transition remains of KT type
when the XY model is coupled to gravity. We also examine whether the
universality we discovered in our earlier work on various Potts models with the
same value of the central charge, $c$, carries over to the XY model, which has
$c=1$.
|
hep-lat/9206015
| 727,360 |
We construct a Goulian-Li-type continuation in the number of insertions of
the cosmological constant operator which is no longer restricted to one
dimensional target space. The method is applied to the calculation of the
three-point and a special four-point correlation function. Various aspects of
the emerging analytical structure are discussed.
|
hep-th/9206053
| 727,361 |
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.
|
hep-ph/9206219
| 727,361 |
We compute correlation functions in $N=2$ non critical superstrings on the
sphere. Our calculations are restrained to the ($s=0$) bulk amplitudes. We show
that the four point function factorizes as a consequence of the non-critical
kinematics, but differently from the $N=0,1$ cases no extra discrete state
appears in the $\hat c\to 1^-$ limit.
|
hep-th/9206054
| 727,361 |
Varieties with log terminal and log canonical singularities are considered in
the Minimal Model Program, see \cite{...} for introduction. In
\cite{shokurov:hyp} it was conjectured that many of the interesting sets,
associated with these varieties have something in common: they satisfy the
ascending chain condition, which means that every increasing chain of elements
terminates. Philosophically, this is the reason why two main hypotheses in the
Minimal Model Program: existence and termination of flips should be true and
are possible to prove.
In this paper we prove that the following two sets satisfy the ascending
chain condition:
1. The set of minimal log discrepancies for $K_X+B$ where $X$ is a surface
with log canonical singularities.
2. The set of groups $(b_1,...b_s)$ such that there is a surface $X$ with log
canonical and numerically trivial $K_X+\sum b_jB_j$. The order on such groups
is defined in a natural way.
|
alg-geom/9206005
| 727,361 |
The dynamical critical exponent of the two-dimensional spin-flip Ising model
is evaluated by a Monte Carlo renormalization group method involving a
transformation in time. The results agree very well with a finite-size scaling
analysis performed on the same data. The value of $z = 2.13 \pm 0.01$ is
obtained, which is consistent with most recent estimates.
|
cond-mat/9206004
| 727,362 |
We present formulas for the Clebsch-Gordan coefficients and the Racah
coefficients for the root of unity representations ($N$-dimensional
representations with $q^{2N}=1$) of $U_q(sl(2))$. We discuss colored vertex
models and colored IRF (Interaction Round a Face) models from the color
representations of $U_q(sl(2))$. We construct invariants of trivalent colored
oriented framed graphs from color representations of $U_q(sl(2))$.
|
hep-th/9206057
| 727,362 |
We examine the relation between Polyakov's formulation of two dimensional
supergravity and gauged Wess-Zumino-Novikov-Witten models.
|
hep-th/9206059
| 727,362 |
Critical circle homeomorphisms have an invariant measure totally singular
with respect to the Lebesgue measure. We prove that singularities of the
invariant measure are of Holder type. The Hausdorff dimension of the invariant
measure is less than 1 but greater than 0.
|
math/9206205
| 727,365 |
We present a concise method to construct a BRST invariant action for the
topological quantum field theories in the Batalin-Vilkovisky antifield
formalism. The BV action that is a solution for the master equation is directly
obtained by means of the extended forms that involve all the required ghosts
and antifields. The BV actions for the non-abelian $BF$ theories (in 4 and
higher dimensions) and the Chern-Simons theory are constructed by means of the
extended form method. An extension of the $BF$ theory in 4-dimensions to
include a ``cosmological term'' is also examined and the close connection with
the topological Yang-Mills theory is indicated.
|
hep-th/9206061
| 727,365 |
It is shown that a renormalizable nonlinear sigma model gives rise to the
effective string theory proposed by Polchinski and Strominger. In the presence
of long string background, the model contains massive world-sheet degrees of
freedom owing to the spontaneous breaking of conformal invariance.
|
hep-th/9206062
| 727,365 |
We derive the BRST cohomology of the G/G topological model for the case of
A^{(1)}_{N-1} . It is shown that at level k={p/q}-N the latter describes the
(p,q) W_N minimal model coupled to $W_N$ gravity (plus some extra ``topological
sectors").
|
hep-th/9206063
| 727,365 |
We present a quantum mechanical model with an infinite number of (discrete)
degrees of freedom, which can serve as a laboratory for multiparticle
production in a collision. There is a cubic coupling between modes without,
however, any problems associated with unstable ground states. The model is
amenable to precise numerical calculations of nonperturbative 1->N transition
amplitudes. On an ordinary workstation, time and memory limitations effectively
restrict N to be $\le\ 8,$ and we present results for this case. We find (1)
that there is reasonable period of time for which there is a constant rate for
the 1->8 transition; (2) at the end of the linear period, the eight particle
amplitude attains a maximum value $\aemax$ which is about $3-4$ orders of
magnitude larger than the comparable amplitude for excitation of the $N=8$
state in the anharmonic oscillator; (3) for values of the coupling in the
region where the Born approximation fails, the amplitude is much larger than
the naive estimates $A_8\simeq \exp{(-1/\g2)}\ $ or $\ \exp{(-8)};$ it is more
like $A_8\sim\exp{(-0.20/\g2)}.$
|
hep-ph/9206224
| 727,365 |
We report results of two investigations of the double-scaling equations for
the unitary matrix models. First, the fixed area partition functions have all
positive coefficients only for the first four critical points. This implies
that the critical points at $k\ge5$ describe non-unitary continuum theories.
Secondly, we examine a conjectured connection to branched polymers, but find
that the scaling solutions of the unitary models do not agree with those of a
particular model describing branched polymers.
|
hep-th/9206064
| 727,365 |
We prove the existence of infinitely many real and imaginary fields whose
5-rank of the class group is >=3.
|
alg-geom/9206006
| 727,365 |
If stable electroweak strings are copiously produced during the electroweak
phase transition, they may contribute significantly to the presently observed
baryon to entropy ratio of the Universe. This analysis establishes the
feasibility of implementing an electroweak baryogenesis scenario without a
first order phase transition.
|
astro-ph/9206001
| 727,365 |
We prove that there exist infinitely many elliptic curves over \Q with given
modular invariant, and rank >=2. Furthermore, there exist infinitely many
elliptic curves over $\Q$ with invariant equal at 0 (resp. 1728) and rank >=6
(resp. >=4).
|
alg-geom/9206007
| 727,365 |
If the quadratic divergence of the standard electroweak model and its local
variation with mass scale are both assumed to be zero, then a modified one-loop
calculation yields m_t = 117 GeV and m_H = 183 GeV. Such a scenario may be the
result of an underlying theory to be revealed at a much higher mass scale.
|
hep-ph/9206226
| 727,365 |
We examine the effect of walking technicolor dynamics on the electroweak $S$
parameter and contrast it with the effect of QCD-like technicolor dynamics. Our
main tools are the operator product expansion for the high-momentum behavior of
the electroweak gauge boson vacuum polarizations and the analyticity of these
polarizations which relate their low and high momentum behaviors. We show that
whereas in large QCD-like technicolor models $S$ is large and positive, in
walking technicolor models a negative contribution is emphasized, related to
the large anomalous dimension of the technifermion condensate. Thus in walking
technicolor $S$ is determined by a large cancellation of two competing effects.
This may result in much smaller values of $S$ than in QCD-like technicolor,
although considerable uncertainties are involved. We conclude that it is
impossible to rule out walking technicolor based on the present experimental
limits on $S$ and the present theoretical technology.
|
hep-ph/9206225
| 727,366 |
We study further the r\^ole of the boundary operator $\O_B$ for macroscopic
loop length in the stable definition of 2D quantum gravity provided by the
$[{\tilde P},Q]=Q$ formulation. The KdV flows are supplemented by an additional
flow with respect to the boundary cosmological constant $\sigma$. We
numerically study these flows for the $m=1$, $2$ and $3$ models, solving for
the string susceptibility in the presence of $\O_B$ for arbitrary coupling
$\sigma$. The spectrum of the Hamiltonian of the loop quantum mechanics is
continuous and bounded from below by $\sigma$. For large positive $\sigma$, the
theory is dominated by the `universal' $m=0$ topological phase present only in
the $[{\tilde P},Q]=Q$ formulation. For large negative $\sigma$, the
non--perturbative physics approaches that of the $[P,Q]=1$ definition, although
there is no path to the unstable solutions of the $[P,Q]=1$ $m$-even models.
|
hep-th/9206066
| 727,366 |
We discuss some aspects of string cosmology with an emphasis on the role
played by the dilaton.
A cosmological scenario based on the assumption that all spatial dimensions
are periodic so that winding modes play an important role is reviewed. A
possibility of a transition from a `string phase' to the `standard' cosmology
via a radiation dominated era and inflation is analysed. We also summarise some
recent results about time dependent solutions of tree level string equations.
|
hep-th/9206067
| 727,366 |
The basic tool for the study of the electroweak phase transition is $V_{eff}
(\phi,T)$, the one-loop finite-temperature effective potential, improved by
all-loop resummations of the most important infrared contributions. In this
paper we perform, as a first step towards a full analysis of the Standard Model
case, a detailed study of the effective potential of the scalar theory. We show
that subleading corrections to the self-energies lead to spurious terms, linear
in the field-dependent mass $m(\phi)$, in the daisy-improved effective
potential. Consistency at subleading order requires the introduction of
superdaisy diagrams, which prevent the appearance of linear terms. The
resulting $V_{eff}(\phi,T)$ for the scalar theory hints at a phase transition
which is either second-order or very weakly first-order.
|
hep-ph/9206227
| 727,366 |
This lecture surveys a few loosely related topics, ranging from the scarcity
of quantum field theories -- and the role that this has played, and still
plays, in physics -- to paradoxes involving black holes in soluble two
dimensional string theory and the question of whether naked singularities might
be of even greater interest to string theorists than black holes.
|
hep-th/9206069
| 727,366 |
We compare the implications for 7Be and pp neutrinos of the two MSW fits to
the new GALLEX solar neutrino measurements . Small mixing angle solutions tend
to suppress the former as electron-neutrinos, but not the latter, and large
angle solutions tend to reduce both by about a factor of 2. The consequences
for BOREXINO and similar solar neutrino--electron scattering experiments are
discussed.
|
hep-ph/9206228
| 727,366 |
Semilocal defects are those formed in field theories with spontaneously
broken symmetries, where the vacuum manifold $M$ is fibred by the action of the
gauge group in a non-trivial way. Studied in this paper is the simplest such
class of theories, in which $M\simeq S^{2N-1}$, fibred by the action of a local
$U(1)$ symmetry. Despite $M$ having trivial homotopy groups up to $\pi_{2N-2}$,
this theory exhibits a fascinating variety of defects: vortices, or semilocal
strings; monopoles (on which the strings terminate); and (when $N=2$) textures,
which may be stabilised by their associated magnetic field to produce a
skyrmion.
|
hep-ph/9206229
| 727,366 |
The universality of $e-\mu-\tau$ interactions may only be an accidental
approximate symmetry analogous to that of flavor SU(2) and SU(3). This was
specifically realized by an extension of the standard model proposed in 1981.
Two key predictions are that the $\tau$ lifetime should be longer and that the
$\rho$ parameter measured at the Z peak should have an additional negative
contribution. These are consistent with present precision electroweak
measurements. A future decisive test of this model would be the discovery of
new W and Z bosons with nearly degenerate masses of a few TeV.
|
hep-ph/9206231
| 727,366 |
The formation and semi-classical evaporation of two-dimensional black holes
is studied in an exactly solvable model. Above a certain threshold energy flux,
collapsing matter forms a singularity inside an apparent horizon. As the black
hole evaporates the apparent horizon recedes and meets the singularity in a
finite proper time. The singularity emerges naked and future evolution of the
geometry requires boundary conditions to be imposed there. There is a natural
choice of boundary conditions which match the evaporated black hole solution
onto the linear dilaton vacuum. Below the threshold energy flux no horizon
forms and boundary conditions can be imposed where infalling matter is
reflected from a time-like naked singularity. All information is recovered at
spatial infinity in this case.
|
hep-th/9206070
| 727,366 |
The SU(3) breaking effects due to light quark masses on heavy meson masses,
decay constants ($F_{D}, F_{D_{s}}$) and the form factor for semileptonic
$\overline{B}\rightarrow D^{(\ast)} l\bar{\nu}_{l}$ transitions are formulated
in chiral perturbation theory, using a heavy meson effective Lagrangian and
expanding in inverse powers of the heavy meson mass. To leading order in this
expansion, the leading chiral logarithms and the required counterterms are
determined. At this level, a non-analytic correction to the mass splittings of
${\cal O}(p^3)$ appears, similar the the one found in light baryons. The
correction to $F_{D_{s}}/F_{D}$ is roughly estimated to be of the order of
$10\%$ and, therefore, experimentally accessible, while the correction to the
form factor is likely to be substantially smaller. We explicitly check that the
heavy quark symmetry is preserved by the chiral loops.
|
hep-ph/9206230
| 727,366 |
Under the axisymmetry and under the invarance of simultaneous inversion of
time and azimuthal angle, we show that the axionic Kerr black hole is the ${\it
unique}$ stationary solution of the minimal coupling theory of gravity and the
Kalb-Ramond field, which has a regular event horizon, is asymptotically flat
and has a finite axion field strength at event horizon.
|
hep-th/9206068
| 727,366 |
We consider grand unified theories with superconducting cosmic strings and
which admit the mechanism for generating primordial magnetic fields recently
discussed by Vachaspati. We show that these models are severely constrained by
cosmological arguments. Quite generically, either stable springs or vortons
will form. Provided the mass per unit length of the strings is sufficiently
large, these stable configurations will overclose the Universe.
|
hep-ph/9206232
| 727,367 |
We discuss the quantum theory of 1+1 dimensional dilaton gravity, which is an
interesting model with analogous features to the spherically symmetric
gravitational systems in 3+1 dimensions. The functional measures over the
metrics and the dilaton field are explicitly evaluated and the diffeomorphism
invariance is completely fixed in conformal gauge by using the technique
developed in the two dimensional quantum gravity. We argue the relations to the
ADM formalism. The physical state conditions reduce to the usual Wheeler-DeWitt
equations when the dilaton $\df^2 ~ (=\e^{-2\phi}) $ is large enough compared
with $\kappa =(N-51/2)/12$, where $N $ is the number of matter fields. This
corresponds to the large mass limit in the black hole geometry. A singularity
appears at $\df^2 =\kappa (>0) $. The final stage of the black hole evaporation
corresponds to the region $\df^2 \sim \kappa $, where the Liouville term
becomes important, which just comes from the measure of the metrics. If $\kappa
< 0 $, the singularity disappears.
|
hep-th/9206071
| 727,367 |
A generalized flux problem with Abelian and non-Abelian fluxes is considered.
In the Abelian case we shall show that the generalized flux problem for
tight-binding models of noninteracting electrons on either $2n$ or $2n+1$
dimensional lattice can always be reduced to a $n$ dimensional hopping problem.
A residual freedom in this reduction enables to identify equivalence classes of
hopping Hamiltonians which have the same spectrum. In the non-Abelian case the
reduction is not possible in general unless the flux tensor factorizes into an
Abelian one times an element of the corresponding algebra.
|
cond-mat/9206005
| 727,367 |
The ability to now make measurements of Be and B as well as put constraints
on \lisix\ abundances in metal-poor stars has led to a detailed reexamination
of Big Bang Nucleosynthesis in the $A\groughly6$ regime. The nuclear reaction
network has been significantly expanded with many new rates added. It is
demonstrated that although a number of $A>7$ reaction rates are poorly
determined, even with extreme values chosen, the standard homogeneous model is
unable to produce significant yields (Be/H and B/H $<10^{-17}$ when $A\le7$
abundances fit) above $A=7$ and the \liseven/\lisix\ ratio always exceeds 500.
We also preliminarily explore inhomogeneous models, such as those inspired by a
first order quark-hadron phase transition, where regions with high
neutron/proton ratios can allow some leakage up to $A>7$. However models that
fit the $A\le7$ abundances still seem to have difficulty in obtaining
significant $A>7$ yields.
|
astro-ph/9206002
| 727,367 |
The statistical mechanics of directed line-like objects, such as directed
polymers in an external field, strands of dipoles in both ferro- and
electrorheological fluids, and flux lines in high-$T_{\tiny C}$ superconductors
bears a close resemblance to the quantum mechanics of bosons in $2+1$
dimensions. We show that single component and binary mixture critical phenomena
in these systems are in the universality class of three dimensional uniaxial
dipolar ferromagnets and ferroelectrics. Our results also apply to films of two
superfluid species undergoing phase separation well below their
$\lambda$-points near $T=0$. In the case of directed polymers and
electrorheological fluids we analyze the effects of free ends occurring in the
sample as well as a novel directionally-dependent compressibility.
|
cond-mat/9206006
| 727,367 |
We write a Ginzburg-Landau Hamiltonian for a charged order parameter
interacting with a background electromagnetic field in 2+1 dimensions. Using
the method of Lund we derive a collective coordinate action for vortex defects
in the order parameter and demonstrate that the vortices are charged. We
examine the classical dynamics of the vortices and then quantize their motion,
demonstrating that their peculiar classical motion is a result of the fact that
the quantum motion takes place in the lowest Landau level. The classical and
quantum motion in two dimensional regions with boundaries is also investigated.
The quantum theory is not invariant under magnetic translations. Magnetic
translations add total time derivative terms to the collective action, but no
extra constants of the motion result.
|
hep-th/9206073
| 727,367 |
We compare the anisotropies in the cosmic microwave background radiation
measured by the COBE experiment to the predictions of cosmic strings. We use an
analytic model for the $\Delta T/T$ power spectrum that is based on our
previous numerical simulations to show that the COBE results imply a value for
the string mass per unit length, $\mu$ under the assumption that cosmic strings
are the source of the measured anisotropy. We find $G\mu = 1.5\pm 0.5 \times
10^{-6}$ which is consistent with the value of $\mu$ thought to be required for
cosmic strings to seed galaxy formation.
|
hep-ph/9206233
| 727,367 |
A Hopf texture is a vacuum field configuration of isovector fields which is
an onto map from the space as a large three sphere to the vacuum manifold
$S^2$. We construct a Hopf texture with spherically symmetric energy density
and discuss the topological charge. A Hopf texture collapses, and we study the
collapse process numerically. In our simulations, it is clear that a Hopf
texture does not decay into a pair of monopoles. We also argue that the
probability of forming Hopf textures in random processes is very small compared
to that of global monopoles.
|
hep-ph/9206234
| 727,367 |
We calculate contributions to the finite temperature effective action for the
electroweak phase transition (EWPT) at $\O(g^4)$, {\it i.e.} at second order in
$(g^2 T/\M)$ and all orders in $(g^2 T^2/\M^2)$. This requires plasma-mass
corrections in the calculation of the effective potential, inclusion of the
``lollipop'' diagram, and an estimate of derivative corrections. We find the
EWPT remains too weakly first-order to drive baryogenesis. We calculate some
one loop kinetic energy corrections using both functional and diagrammatic
methods; these may be important for saddlepoint configurations such as the
bounce or sphaleron.
|
hep-ph/9206235
| 727,368 |
We present a derivation of the low energy effective action of an extended
Nambu Jona-Lasinio (ENJL) model to $O(p^4)$ in the chiral counting. Two
alternative scenarios are considered on how the ENJL model could originate as a
low energy approximation to QCD. The low energy effective Lagrangian we derive
includes the usual pseudoscalar Goldstone modes, as well as the lower scalar,
vector and axial-vector degrees of freedom. By taking appropriate limits, we
recover most of the effective low-energy models discussed in the literature; in
particular the gauged Yang-Mills vector Lagrangian, the Georgi-Manohar
constituent quark-meson model, and the QCD effective action approach model.
Another property of the ensuing effective Lagrangian is that it incorporates
most of the short-distance relations which follow from QCD. (We derive these
relations in the presence of all possible gluonic interactions to leading order
in the $1/N_c$-expansion.) Finally the numerical predictions are compared to
the experimental values of the low energy parameters
|
hep-ph/9206236
| 727,368 |
We consider two types of generalized self-duality conditions for Yang-Mills
fields on paracomplex manifolds of arbitrary dimension. We then specialize to
$3+3$ dimensions and show how one can obtain the KP equation from these
self-duality conditions on $SL(2,R)$ valued gauge fields.
|
hep-th/9206076
| 727,368 |
Thesis includes review on the large order behaviour of perturbation theory in
quantum mechanical and field theory models; generalization of the Borel
summability and strong asymptotic conditions to various (including horn-shaped)
regions; discussion of analytic aspects of perturbation theory; examples which
demonstrate differences between the Borel summability and generalized one;
application to the Rayleigh-Schr\"{o}dinger perturbation theory and to the
definition of the operator valued functions. The new summability methods
converges in the whole Mittag-Leffeler star of an analytical function and as
such is useful for localization of singularities in the complex plane. Their
position can be calculated even analytically provided large order behaviour of
the Taylor series is known. Method can be implemented numerically as well.
|
hep-th/9206074
| 727,368 |
A novel approach to S =1/2 antiferromagnets with strong fluctuations based on
the representation of spin-1/2 operators as bylinear forms of real (Majorana)
fermions is suggested. This representation has the advantage of being
irreducible without any constraints on the fermionic Hilbert space. This
property allows to derive an effective Hamiltonian for low-lying excitations in
the spin liquid state. It is proven that these excitations are S = 1 real
fermions.
|
cond-mat/9206007
| 727,368 |
We present a conformal field theory -- obtained from a gauged WZW model --
that describes a closed, inhomogeneous expanding and recollapsing universe in
$3+1$ dimensions. A possible violation of cosmic censorship is avoided because
the universe recollapses just when a naked singularity was about to form. The
model has been chosen to have $c=4$ (or $\widehat c=4$ in the supersymmetric
case), just like four dimensional Minkowski space.
|
hep-th/9206078
| 727,368 |
We calculate the flux of ultra high energy photons from individual ordinary
(i.e. non-superconducting) cosmic strings and compare the results with the
sensitivity of current and proposed TeV and EeV telescopes. Our calculations
give only upper limits for the gamma ray flux, since the source of the photons,
jets from particle production at cusps, may be weakened by back reaction
effects. For the usual cosmic distribution of strings, the predicted bursts
from strings with the value of mass per unit length associated with galaxy
formation or light strings may just be detectable. A diffuse gamma ray
background from light strings may also be seen by the Fly's Eye detector at
above $7 \times 10^{10}$ GeV.
|
astro-ph/9206003
| 727,368 |
The static stationary axially symmetric background ("infinite cosmic string")
of the $D=4$ string theory provided with an axion charge is studied in the
effective theory approach. The most general exact solution is constructed. It
is found that the Kalb-Ramond axion charge, present in the string topology
$R^{3} \times S^{1}$, produces nontrivial gravitational field configurations
which feature horizons. The corresponding ``no-hair'' theorems are proved which
stress uniqueness of black strings. Connection of the solutions with the gauged
WZWN sigma model constructions on the world sheet is discussed since they are
the only target spaces which hide their singularities behind horizons, and thus
obey the cosmic censorship conjecture.
|
hep-th/9206079
| 727,368 |
We study the interface between soft and hard QCD at high energy and small
momentum transfer. At LHC and SSC energies, we find that a cutoff BFKL equation
leads one to expect a measurable perturbative component in traditionally soft
processes. We show that the total cross section could become as large as 175 mb
(122 mb) and the rho parameter 0.40 (0.25) at the SSC (LHC).
|
hep-ph/9206237
| 727,368 |
We investigate the nature of the ground ring of c=1 string theory at the
special A-D-E points in the c=1 moduli space associated to discrete subgroups
of SU(2). The chiral ground rings at these points are shown to define the A-D-E
series of singular varieties introduced by Klein. The non-chiral ground rings
relevant to closed-string theory are 3 real dimensional singular varieties
obtained as U(1) quotients of the Kleinian varieties. The unbroken symmetries
of the theory at these points are the volume-preserving diffeomorphisms of
these varieties. The theory of Kleinian singularities has a close relation to
that of complex hyperKahler surfaces, or gravitational instantons. We speculate
on the relevance of these instantons and of self-dual gravity in c=1 string
theory.
|
hep-th/9206080
| 727,370 |
The gauge dependence of the hot gluon self energy is examined in the context
of Pisarski's method for resumming hard thermal loops. Braaten and Pisarski
have used the Ward identities satisfied by the hard corrections to the n-point
functions to argue the gauge fixing independence of the leading order resummed
QCD plasma damping rate in covariant and strict Coulomb gauges. We extend their
analysis to include all linear gauges that preserve rotational invariance and
display explicitly the conditions required for gauge fixing independence. It is
shown that in covariant gauges the resummed damping constant is gauge fixing
independent only if an infrared regulator is explicitly maintained throughout
the calculation.
|
hep-ph/9206239
| 727,370 |
A self-consistent renormalization scheme at finite temperature and zero
momentum is used together with the finite temperature renormalization group to
study the temperature dependence of the mass and the coupling to one-loop order
in the $(\phi^3)_6$- and $(\phi^4)_4$-models. It is found that the critical
temperature is shifted relative to the naive one-loop result and the coupling
constants at the critical temperature get large corrections. In the high
temperature limit of the $\phiff$-model the coupling decreases.
|
hep-ph/9206240
| 727,371 |
We construct an effective Lagrangian describing the interaction of soft pions
and kaons with mesons containing a heavy quark and light degrees of freedom in
an orbital $p$ wave. The formalism is easily extended to heavy mesons and
baryons in arbitrary excited states. We calculate the leading contributions to
the strong decays $\dtwo\to\d\pi$, $\dtwo\to\dstar\pi$ and $\done\to\dstar\pi$.
We confirm the relations between the rates previously obtained by Isgur and
Wise using heavy quark symmetry, and find that the absolute widths are
consistent with na\"\i ve power counting. We also estimate the branching ratios
for the two pion decays $\dtwo\to\dstar\pi\pi$, $\done\to\dstar\pi\pi$ and
$\done\to\d\pi\pi$, which are dominated by pole graphs. Our predictions depend
on the masses and widths of the as yet unseen scalar-pseudovector $p$-wave
doublet. Heavy quark spin symmetry predicts $\Gamma(\dtwo\to\dstar\pi\pi):
\Gamma(\done\to\dstar\pi\pi):\Gamma(\done\to\d\pi\pi)=3:1:2$, but this relation
is badly violated in practice because $1/M$ effects arising purely from
kinematics are large.
|
hep-ph/9206241
| 727,371 |
The three-dimensional, three-state Potts model is studied as a paradigm for
high temperature quantum chromodynamics. In a high statistics numerical
simulation using a Swendson-Wang algorithm, we study cubic lattices of
dimension as large as $64^3$ and measure correlation functions on long lattices
of dimension $20^2\times 120$ and $30^2\times 120$. These correlations are
controlled by the spectrum of the transfer matrix. This spectrum is studied in
the vicinity of the phase transition. The analysis classifies the spectral
levels according to an underlying $S_3$ symmetry. Near the phase transition the
spectrum agrees nicely with a simple four-component hamiltonian model. In the
context of this model, we find that low temperature ordered-ordered interfaces
nearly always involve a disordered phase intermediate. We present a new
spectral method for determining the surface tension between phases.
|
hep-lat/9206017
| 727,371 |
Canonical forms are given for the nilpotent BRS operator $\d$ and the
covariant `loop space' derivative ${\cal D}_{\m}$ for the p-brane fields for
all odd p. The defining characteristic of ${\cal D}_{\m}$ is that it is a
functional derivative operator which generalizes the ordinary functional
derivative and also commutes with $\d$. Methods of construction for the
canonical forms are discussed.
|
hep-th/9206082
| 727,371 |
We consider a gauge model based on $SU(3)\otimes U(1)$ symmetry in which the
lepton number is violated explicitly by charged scalar and gauge bosons,
including a vector field with double electric charge.
Although there exist in the literature several models based on a
$SU(3)\otimes U(1)$ gauge symmetry, our model has a different representation
content and a quite different new physics at an, in principle, arbitrary mass
scale.
This is possibly the simplest way to enlarge the gauge group $SU_L(2)\otimes
U_Y(1)$ in order to have doubly charged gauge bosons, without losing the
natural features of the standard electroweak model. The price we must pay is
the introduction of exotic quarks, with electric charge $5/3$ and $-4/3$.
A previous version of the model was considered several months ago concerning
the possibility that in this kind of models neutrinoless double beta decay
proceeds even for massless neutrinos and with scalar exchange instead of vector
exchange.
Our work is in press in Physical Review D.
|
hep-ph/9206242
| 727,371 |
The interplay of spectroscopy, scaling laws and critical indices is studied
in strongly coupled quenched QED. Interpreted as a model of technicolor having
strong interactions at short distances, we predict the techni-meson mass
spectrum in a simplified model of a dynamically generated top quark mass $M_f$.
Our results support the strict inequality that the techni-sigma mass $M_\sigma$
is less than twice the dynamical quark mass $M_f$, and confirm that the
techni-pion is a Nambu-Goldstone boson. The level ordering $0 = M_\pi <
M_\sigma < 2M_f < M_\rho < M_{a1} $ is found.An equation of state, and scaling
laws are derived for the techni-meson masses by exploiting correlation length
scaling. The resulting universality relations are confirmed by simulations on
$16^4$, $32\times 16^3$ and $32^4$ lattices. The anomalous dimension $\eta$ is
measured to be approximatively $0.50$ in good agreement with past lattice
simulations and hyperscaling relations, as well as with the analytic solution
of the quenched, planar gauged Nambu-Jona Lasinio model solved by continuum
Schwinger-Dyson equation techniques.
|
hep-lat/9206018
| 727,371 |
The Higgs contribution to the effective potential appears to be complex. How
do we interpret this, and how should we modify the calculation to calculate
physical quantities such as the critical bubble free energy?
|
hep-ph/9206243
| 727,372 |
In this paper we investigate the internal dynamics of the LMC cluster NGC
1978 through the use of Photometric (CCD images) and kinematic (stellar radial
velocities) data. We apply a variety of dynamical models to this data,
including multi-mass King-Michie models and rotating and non-rotating oblate
spheroid models. We discuss the cluster mass-to-light ratio and place
constraints on the cluster mass function.
|
astro-ph/9206004
| 727,372 |
In an $e^- p$ collider, a striking signature for a dilepton gauge boson is
\ep \ ; this cross-section is calculated by using the helicity amplitude
technique. At HERA, with center-of-mass energy $\sqrt s = 314 GeV$, a dilepton
mass above $150 GeV$ is inaccessible but at LEPII-LHC, with a center-of-mass
energy $\sqrt s = 1790 GeV $, masses up to 650 GeV can be discovered. In an
$e^+ e^-$ collider, the signature is \ee \ . The cross-sections of this process
are also calculated for the center-of-mass energies $\sqrt s = 200, 500$ and
$1000 GeV$.
|
hep-ph/9206244
| 727,372 |
In the standard scenario, the electroweak phase transition is a first order
phase transition which completes by the nucleation of critical bubbles.
Recently, there has been speculation that the standard picture of the
electroweak phase transition is incorrect. Instead, it has been proposed that
throughout the phase transition appreciable amounts of both broken and unbroken
phases of $SU(2)$ coexist in equilibrium. I argue that this can not be the
case. General principles insure that the universe will remain in a homogenous
state of unbroken $SU(2)$ until the onset of critical bubble production.
In addition, an analytic treatment of the one Higgs doublet, electroweak
phase transition in the standard model and minimal extensions is reviewed.
Results from the thin wall approximation are compared to results obtained using
the Lindes' action. Perhaps the most important quantitative result we can get
from an analysis of the phase transition is determination of $\vevphi$ when the
phase transition completes. For Higgs boson masses above the current
experimental limit, the thin wall approximation determines the value of
$\vevphi$ at the end of the phase transition to an accuracy of better than
three percent.
|
hep-ph/9206245
| 727,372 |
The capability of string theories to reproduce at low energy the observed
pattern of quark and lepton masses and mixing angles is examined, focusing the
attention on orbifold constructions, where the magnitude of Yukawa couplings
depends on the values of the deformation parameters which describe the size and
shape of the compactified space. A systematic exploration shows that for $Z_3$,
$Z_4$, $Z_6$--I and possibly $Z_7$ orbifolds a correct fit of the physical
fermion masses is feasible. In this way the experimental masses, which are
low--energy quantities, select a particular size and shape of the compactified
space, which turns out to be very reasonable (in particular the modulus $T$
defining the former is $T=O(1)$). The rest of the $Z_N$ orbifolds are rather
hopeless and should be discarded on the assumption of a minimal $SU(3)\times
SU(2)\times U(1)_Y$ scenario. On the other hand, due to stringy selection
rules, there is no possibility of fitting the Kobayashi--Maskawa parameters at
the renormalizable level, although it is remarked that this job might well be
done by non--renormalizable couplings.
|
hep-th/9206083
| 727,372 |
We explore the analogy between quark confinement and the Meissner effect in
superconductors. We measure the response of color-magnetic "supercurrents" from
Dirac magnetic monopoles to the presence of a static quark-antiquark pair in
four dimensional U(1) lattice gauge theory. Our results indicate that in the
confined phase these currents screen the color-electric flux due to the quarks
in an electric analogy of the Meisner effect. We show that U(1) lattice guage
theory obeys both a dual London equation and an electric fluxoid quantization
condition.
|
hep-lat/9206019
| 727,372 |
The complete quantum theory of covariant closed strings is constructed in
detail. The action is defined by elementary vertices satisfying recursion
relations that give rise to Jacobi-like identities for an infinite chain of
string field products. The genus zero string field algebra is the homotopy Lie
algebra $L_\infty$, and the higher genus algebraic structure implies the
Batalin-Vilkovisky (BV) master equation. From these structures on the off-shell
state space, we show how to derive the $L_\infty$ algebra, and the BV equation
on physical states, recently constructed in d=2 string theory. The string
diagrams are surfaces with minimal area metrics, foliated by closed geodesics
of length $2\pi$. These metrics generalize quadratic differentials in that
foliation bands can cross. The string vertices are succinctly characterized;
they include the surfaces whose foliation bands are all of height smaller than
$2\pi$.
--While this is not a review paper, an effort was made to give a fairly
complete and accessible account of the quantum closed string field theory.--
|
hep-th/9206084
| 727,372 |
Starting from the Wess-Zumino action associated to the super Weyl anomaly, we
determine the local counterterm which allows to pass from this anomaly to the
chirally split superdiffeomorphism anomaly (as defined on a compact super
Riemann surface without boundary). The counterterm involves the graded
extension of the Verlinde functional and the results can be applied to the
study of holomorphic factorization of partition functions in superconformal
field theory.
|
hep-th/9206089
| 727,372 |
We discuss weak-vector-boson scattering, at next-to-leading order in QCD,
within the framework of hadronic structure functions. We use this approach to
calculate the Higgs-boson production cross section via vector-boson fusion at
the LHC/SSC; we find a modest increase over the leading-order prediction. We
also give expressions for the distribution of vector bosons in a proton
(effective-$W$ approximation) including ${\cal O} (\alpha_s)$ corrections.
|
hep-ph/9206246
| 727,373 |
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