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We give a formula for the derivatives of a correlation function of composite
operators with respect to the parameters (i.e., the strong fine structure
constant and the quark mass) of QCD in four-dimensional euclidean space. The
formula is given as spatial integration of the operator conjugate to a
parameter. The operator product of a composite operator and a conjugate
operator has an unintegrable part, and the formula requires divergent
subtractions. By imposing consistency conditions we derive a relation between
the anomalous dimensions of the composite operators and the unintegrable part
of the operator product coefficients.
|
hep-th/9205085
| 727,343 |
We investigate non-commutative differential calculus on the supersymmetric
version of quantum space where the non-commuting super-coordinates consist of
bosonic as well as fermionic (Grassmann) coordinates. Multi-parametric quantum
deformation of the general linear supergroup, $GL_q(m|n)$, is studied and the
explicit form for the ${\hat R}$-matrix, which is the solution of the
Yang-Baxter equation, is presented. We derive the quantum-matrix commutation
relation of $GL_q(m|n)$ and the quantum superdeterminant. We apply these
results for the $GL_q(m|n)$ to the deformed phase-space of supercoordinates and
their momenta, from which we construct the ${\hat R}$-matrix of q-deformed
orthosymplectic group $OSp_q(2n|2m)$ and calculate its ${\hat R}$-matrix. Some
detailed argument for quantum super-Clifford algebras and the explict
expression of the ${\hat R}$-matrix will be presented for the case of
$OSp_q(2|2)$.
|
hep-th/9205087
| 727,344 |
The frequency dependence of third harmonic generation (THG) in C_{60} is
calculated, making use of a tight-binding model for pi-electrons. The
magnitudes of the THG, about 10^{-12} esu, near zero frequency, agree with
those in experiments for the low-energy region. We can also explain the order
of the magnitude, 10^{-11} esu, around the three-photon resonance peak due to
the lowest allowed excitation, recently measured by Meth et al. At higher
energies, we predict a large enhancement of the THG at 3 omega \sim 6eV as a
result of double resonance enhancement.
|
cond-mat/9205012
| 727,344 |
The present paper is devoted to the study of geometry of Batalin-Vilkovisky
quantization procedure. The main mathematical objects under consideration are
P-manifolds and SP-manifolds (supermanifolds provided with an odd symplectic
structure and, in the case of SP-manifolds, with a volume element). The
Batalin-Vilkovisky procedure leads to consideration of integrals of the
superharmonic functions over Lagrangian submanifolds. The choice of Lagrangian
submanifold can be interpreted as a choice of gauge condition; Batalin and
Vilkovisky proved that in some sense their procedure is gauge independent. We
prove much more general theorem of the same kind. This theorem leads to a
conjecture that one can modify the quantization procedure in such a way as to
avoid the use of the notion of Lagrangian submanifold. In the next paper we
will show that this is really so at least in the semiclassical approximation.
Namely the physical quantities can be expressed as integrals over some set of
critical points of solution S to the master equation with the integrand
expressed in terms of Reidemeister torsion. This leads to a simplification of
quantization procedure and to the possibility to get rigorous results also in
the infinite-dimensional case. The present paper contains also a compete
classification of P-manifolds and SP-manifolds. The classification is
interesting by itself, but in this paper it plays also a role of an important
tool in the proof of other results.
|
hep-th/9205088
| 727,344 |
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}$.
|
hep-ph/9205233
| 727,344 |
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.
|
hep-ph/9205234
| 727,344 |
We study compressible fluid flow in narrow two-dimensional channels using a
novel molecular dynamics simulation method. In the simulation area, an upstream
source is maintained at constant density and temperature while a downstream
reservoir is kept at vacuum. The channel is sufficiently long in the direction
of the flow that the finite length has little effect on the properties of the
fluid in the central region. The simulated system is represented by an
efficient data structure, whose internal elements are created and manipulated
dynamically in a layered fashion. Consequently the code is highly efficient and
manifests completely linear performance in simulations of large systems. We
obtain the steady-state velocity, temperature, and density distributions in the
system. The velocity distribution across the channel is very nearly a quadratic
function of the distance from the center of the channel and reveals velocity
slip at the boundaries; the temperature distribution is only approximately a
quartic function of this distance from the center to the channel. The density
distribution across the channel is non-uniform. We attribute this
non-uniformity to the relatively high Mach number, approximately 0.5, in the
fluid flow. An equation for the density distribution based on simple
compressibility arguments is proposed; its predictions agree well with the
simulation results. Validity of the concept of local dynamic temperature and
the variation of the temperature along the channel are discussed.
|
cond-mat/9205013
| 727,344 |
We study the algebraic geometrical background of the Penner--Kontsevich
matrix model with the potential $N\alpha \tr {\bigl(- \fr 12 \L X\L X +\log
(1-X)+X\bigr)}$. We show that this model describes intersection indices of
linear bundles on the discretized moduli space right in the same fashion as the
Kontsevich model is related to intersection indices (cohomological classes) on
the Riemann surfaces of arbitrary genera. The special role of the logarithmic
potential originated from the Penner matrix model is demonstrated. The boundary
effects which was unessential in the case of the Kontsevich model are now
relevant, and intersection indices on the discretized moduli space of genus $g$
are expressed through Kontsevich's indices of the genus $g$ and of the lower
genera.
|
hep-th/9205106
| 727,344 |
We investigate the phase structure of three-dimensional quantum gravity
coupled to an Ising spin system by means of numerical simulations. The quantum
gravity part is modelled by the summation over random simplicial manifolds, and
the Ising spins are located in the center of the tetrahedra, which constitute
the building blocks of the piecewise linear manifold. We find that the coupling
between spin and geometry is weak away from the critical point of the Ising
model. At the critical point there is clear coupling, which however does not
seem to change the first order transition between the ``hot'' and ``cold''
phase of three dimensional simplicial quantum gravity observed earlier.
|
hep-lat/9205021
| 727,344 |
We investigate the question of parity breaking in three-dimensional Euclidean
SU(2) gauge-Higgs theory by Monte Carlo simulations. We observe no sign of
spontaneous parity breaking in the behaviour of both local and non-local gauge
invariant operators. However, the presence of parity odd terms in the action
can induce a phase transition to a parity odd ground state which is
characterized by a Chern-Simons like condensate. The implications for various
proposed scenarios of fermion number non-conservation is discussed.
|
hep-lat/9205022
| 727,344 |
Previous analyses on the gauge invariance of the action for a generally
covariant system are generalized. It is shown that if the action principle is
properly improved, there is as much gauge freedom at the endpoints for an
arbitrary gauge system as there is for a system with ``internal'' gauge
symmetries. The key point is to correctly identify the boundary conditions for
the allowed histories and to include the appropriate end-point contribution in
the action. The path integral is then discussed. It is proved that by employing
the improved action, one can use time-independent canonical gauges even in the
case of generally covariant theories. From the point of view of the action and
the path integral, there is thus no conceptual difference between general
covariance and ``ordinary gauge invariance''. The discussion is illustrated in
the case of the point particle, for which various canonical gauges are
considered.
|
hep-th/9205092
| 727,344 |
Mirror fermions appear naturally in lattice formulations of the standard
model. The phenomenological limits on their existence and discovery limits at
future colliders are discussed. After an introduction of lattice actions for
chiral Yukawa-models, a recent numerical simulation is presented. In
particular, the emerging phase structure and features of the allowed region in
renormalized couplings are discussed.
|
hep-lat/9205023
| 727,344 |
We define a lattice statistical model on a triangulated manifold in four
dimensions associated to a group $G$. When $G=SU(2)$, the statistical weight is
constructed from the $15j$-symbol as well as the $6j$-symbol for recombination
of angular momenta, and the model may be regarded as the four-dimensional
version of the Ponzano-Regge model. We show that the partition function of the
model is invariant under the Alexander moves of the simplicial complex, thus it
depends only on the piecewise linear topology of the manifold. For an
orientable manifold, the model is related to the so-called $BF$ model. The
$q$-analogue of the model is also constructed, and it is argued that its
partition function is invariant under the Alexander moves. It is discussed how
to realize the 't Hooft operator in these models associated to a closed surface
in four dimensions as well as the Wilson operator associated to a closed loop.
Correlation functions of these operators in the $q$-deformed version of the
model would define a new type of invariants of knots and links in four
dimensions.
|
hep-th/9205090
| 727,344 |
A chiral $(N,0) $ supergravity theory in d=2 dimensions for any $N$ and its
induced action can be obtained by constraining the currents of an Osp(N$|$2)
WZWN model. The underlying symmetry algebras are the nonlinear SO(N)
superconformal algebras of Knizhnik and Bershadsky. The case $N=3$ is worked
out in detail. We show that by adding quantum corrections to the classical
transformation rules, the gauge algebra on gauge fields and currents closes.
Integrability conditions on Ward identities are derived. The effective action
is computed at one loop. It is finite, and can be obtained from the induced
action by rescaling the central charge and fields by finite Z factors.
|
hep-th/9205093
| 727,344 |
A distinctive feature of string unification is the possibility of unification
by a non-simply-laced group. This occurs most naturally in four dimensional
type~II string models where the gauge symmetry is realized by Kac-Moody
algebras at different levels. We investigate the running coupling constants and
the one-loop thresholds for such general models. As a specific case, we examine
a $\rm SU(3)\times U(1)\times U(1)$ model and find that the threshold
corrections lead to a small $6\%$ increase in the unification scale.
|
hep-th/9205094
| 727,344 |
We present a new technique for a numerical analysis of the phase structure of
the 2D Hubbard model as a function of the hole chemical potential. The grand
canonical partition function for the model is obtained via Monte Carlo
simulations. The dependence of the hole occupation number on the chemical
potential and the temperature is evaluated. These calculations, together with a
study of the Yang-Lee zeros of the grand canonical partition function, show
evidence of a phase transition at zero temperature and particle density below
half-filling. The binding energy of a pair of holes is calculated in the low
temperature regime and the possibility for pairing is explored.
|
hep-lat/9205024
| 727,344 |
Some exact static solutions for Einstein gravity in 2+1 dimensions coupled to
abelian gauge field are discussed. Some of these solutions are
three-dimensional analogs of the Schwarzschild black holes. The metrics in the
regions inside and outside the horison are connected by the changing of the
Planck mass sign.
|
hep-th/9205095
| 727,344 |
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.
|
hep-ph/9205236
| 727,344 |
In recent work, several classes of solitonic solutions of string theory with
higher-membrane structure have been obtained. These solutions can be classified
according to the symmetry possessed by the solitons in the subspace of the
spacetime transverse to the membrane. Solitons with four-dimensional spherical
symmetry represent instanton solutions in string theory, while those with
three-dimensional spherical symmetry represent magnetic monopole-type
solutions. For both of these classes, we discuss bosonic as well as heterotic
solutions.
|
hep-th/9205091
| 727,344 |
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.
|
hep-ph/9205237
| 727,345 |
We study how fermion number conservation fails in fermion number preserving
regularization schemes. We show that the fermion number have to be carried by
the gauge field configurations with non-zero winding number in this scheme and
this fermion number is not conserved in the presence of instantons. We also
consider other types of regularization scheme which have different global
symmetries. In particular, we point out that the fermion number is conserved in
the lattice chiral gauge theories with the Wilson-Yukawa coupling.
|
hep-lat/9205025
| 727,345 |
We extend the Su-Schrieffer-Heeger model of polyacetylene to C_{60} and
C_{70} molecules, and solve numerically. The calculations of the undoped
systems agree well with the known results. When the system (C_{60} or C_{70})
is doped with one or two electrons (or holes), the additional charges
accumulate almost along an equatorial line of the molecule. The dimerization
becomes weaker almost along the same line. Two energy levels intrude largely in
the gap. The intrusion is larger in C_{70} than in C_{60}. Therefore,
``polarons'' are predicted in doped buckminster- fullerenes. We calculate
optical absorption coefficient for C_{60} in order to look at how ``polarons''
will be observed. It is predicted that there appears a new peak at the lower
energy than the intergap transition peaks. It is also found that C_{60} and
C_{70} are related mutually with respect to electronical structures as well as
lattice geometries. (to be published in Phys. Rev. B 45, June 15 issue)
|
cond-mat/9205014
| 727,345 |
Thermal history of the string universe based on the Brandenberger and Vafa's
scenario is examined. The analysis thereby provides a theoretical foundation of
the string universe scenario. Especially the picture of the initial oscillating
phase is shown to be natural from the thermodynamical point of view. A new tool
is employed to evaluate the multi state density of the string gas. This
analysis points out that the well-known functional form of the multi state
density is not applicable for the important region $T \leq T_H$, and derives a
correct form of it.
|
hep-th/9205096
| 727,345 |
A covariant path integral calculation of the even spin structure contribution
to the one-loop N-graviton scattering amplitude in the type-II superstring
theory is presented. The apparent divergence of the $N=5$ amplitude is resolved
by separating it into twelve independent terms corresponding to different
orders of inserting the graviton vertex operators. Each term is well defined in
an appropriate kinematic region and can be analytically continued to physical
regions where it develops branch cuts required by unitarity. The zero-slope
limit of the $N=5$ amplitude is performed, and the Feynman diagram content of
the low-energy field theory is examined. Both one-particle irreducible (1PI)
and one-particle redicible (1PR) graphs with massless internal states are
generated in this limit. One set of 1PI graphs has the same divergent
dependence on the cut-off as that found in the four-graviton case, and it is
proved that such graphs exist for all~$N$. The 1PR graphs are contributed by
the poles in the world-sheet chiral Green functions.
|
hep-th/9205097
| 727,345 |
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.
|
hep-ph/9205239
| 727,345 |
The general theory of matching conditions is developed for gravitational
theories in two spacetime dimensions. Models inspired from general relativity
and from string theory are considered. These conditions are used to study
collapsing dust solutions in spacetimes with non-zero cosmological constant,
demonstrating how two-dimensional black holes can arise as the endpoint of such
collapse processes.
|
hep-th/9205098
| 727,345 |
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.
|
hep-ph/9205238
| 727,345 |
The process of pattern formation in the two dimensional Swift-Hohenberg
equation is examined through numerical and analytic methods. Dynamic scaling
relationships are developed for the collective ordering of convective rolls in
the limit of infinite aspect ratio. The stationary solutions are shown to be
strongly influenced by the strength of noise. Stationary states for small and
large noise strengths appear to be quasi-ordered and disordered respectively.
The dynamics of ordering from an initially inhomogeneous state is very slow in
the former case and fast in the latter. Both numerical and analytic
calculations indicate that the slow dynamics can be characterized by a simple
scaling relationship, with a characteristic dynamic exponent of $1/4$ in the
intermediate time regime.
|
cond-mat/9205015
| 727,345 |
We put forth a Fierzed hopping expansion for strong coupling Wilson fermions.
As an application, we show that the strong coupling Schwinger model on
parallelogram lattices with nonbacktracking Wilson fermions span, as a function
of the lattice skewness angle, the $\Delta = -1$ critical line of $6$-vertex
models. This Fierzed formulation also applies to backtracking Wilson fermions,
which as we describe apparently correspond to richer systems. However, we have
not been able to identify them with exactly solved models.
|
hep-lat/9205026
| 727,345 |
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.
|
hep-ph/9205240
| 727,345 |
High temperature series expansions of the spin-spin correlation functions of
the RP^{n-1} spin model on the square lattice are computed through order
beta^{8} for general spin dimensionality n. Tables are reported for the
expansion coefficients of the energy per site, the susceptibility and the
second correlation moment.
|
hep-lat/9205027
| 727,345 |
This paper concerns the dynamics of polynomial automorphisms of ${\bf C}^2$.
One can associate to such an automorphism two currents $\mu^\pm$ and the
equilibrium measure $\mu=\mu^+\wedge\mu^-$. In this paper we study some
geometric and dynamical properties of these objects. First, we characterize
$\mu$ as the unique measure of maximal entropy. Then we show that the measure
$\mu$ has a local product structure and that the currents $\mu^\pm$ have a
laminar structure. This allows us to deduce information about periodic points
and heteroclinic intersections. For example, we prove that the support of $\mu$
coincides with the closure of the set of saddle points. The methods used
combine the pluripotential theory with the theory of non-uniformly hyperbolic
dynamical systems.
|
math/9205210
| 727,346 |
We study the interactions of the discrete states with nonzero ghost number in
$c=1$ two-dimensional ($2D$) quantum gravity. By using the vertex operator
representations, it is shown that their interactions are given by the structure
constants of the group of the area preserving diffeomorphism similar to those
of vanishing ghost number. The effective action for these states is also worked
out. The result suggests the whole system has a BRST-like symmetry.
|
hep-th/9205101
| 727,346 |
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.
|
hep-ph/9205241
| 727,346 |
I show that the generalized Beltrami differentials and projective connections
which appear naturally in induced light cone $W_n$ gravity are geometrical
fields parametrizing in one-to-one fashion generalized projective structures on
a fixed base Riemann surface. I also show that $W_n$ symmetries are nothing but
gauge transformations of the flat ${SL}(n,{\bf C})$ vector bundles canonically
associated to the generalized projective structures. This provides an original
formulation of classical light cone $W_n$ geometry. From the knowledge of the
symmetries, the full BRS algebra is derived. Inspired by the results of recent
literature, I argue that quantum $W_n$ gravity may be formulated as an induced
gauge theory of generalized projective connections. This leads to projective
field theory. The possible anomalies arising at the quantum level are analyzed
by solving Wess-Zumino consistency conditions. The implications for induced
covariant $W_n$ gravity are briefly discussed. The results presented, valid for
arbitrary $n$, reproduce those obtained for $n=2,3$ by different methods.
|
hep-th/9205102
| 727,346 |
We propose a Su-Schrieffer-Heeger type electron-phonon model for C_{60} with
O defects and solve by the adiabatic approximation. Two new properties are
obtained. (1) The dimerization becomes weaker around the oxygen. Two localized
states appear deep in the gap. Optical transition between them is allowed. This
accords with the recent optical absorption data. (2) Oxygens are predicted to
cluster on the surface of $\soc$. PACS numbers: 3640, 7155, 6165, 3120P
|
cond-mat/9205016
| 727,346 |
We find two different q-generalizations of Yang-Mills theories. The
corresponding lagrangians are invariant under the q-analogue of infinitesimal
gauge transformations. We explicitly give the lagrangian and the transformation
rules for the bicovariant q-deformation of $SU(2) \times U(1)$. The gauge
potentials satisfy q-commutations, as one expects from the differential
geometry of quantum groups. However, in one of the two schemes we present, the
field strengths do commute.
|
hep-th/9205103
| 727,346 |
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.
|
hep-ph/9205242
| 727,346 |
Physics in the neighbourhood of a space-time metric singularity is described
by a world-sheet topological gauge field theory which can be represented as a
twisted $N=2$ superconformal Wess-Zumino model with a $W_{1+\infty} \otimes
W_{1+\infty} $ bosonic symmetry. The measurable $W$-hair associated with the
singularity is associated with Wilson loop integrals around gauge defects. The
breaking of $W_{1+\infty}$ $\otimes $ $W_{1+\infty}$ $\rightarrow $
$W_{1+\infty}$ is associated with expectation values for open Wilson lines that
make the metric non-singular away from the singularity. This symmetry breaking
is accompanied by massless discrete `tachyon' states that appear as leg poles
in $S$-matrix elements. The triviality of the $S$-matrix in the high-energy
limit of the $c=1$ string model, after renormalisation by the leg pole factors,
is due to the restoration of double $W$-symmetry at the singularity.
|
hep-th/9205107
| 727,346 |
We review some exact solitonic solutions of string theory with
higher-membrane structure. These include an axionic instanton solution of
bosonic string theory as well as multi-instanton and multimonopole solutions of
heterotic string theory. The heterotic solutions reveal some interesting
aspects of string theory as a theory of quantum gravity.
|
hep-th/9205108
| 727,347 |
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.
|
hep-ph/9205244
| 727,347 |
The Batalin-Vilkovisky antifield action for the BF theories is constructed by
means of the extended form method. The BRST invariant BV antifield action is
directly written down by making use of the extended forms that involve all the
required ghosts and antifields.
|
hep-th/9205111
| 727,347 |
A new open spin chain hamiltonian is introduced. It is both integrable
(Sklyanin`s type $K$ matrices are used to achieve this) and invariant under
${\cal U}_{\epsilon}(sl(2))$ transformations in nilpotent irreps for
$\epsilon^3=1$. Some considerations on the centralizer of nilpotent
representations and its representation theory are also presented.
|
hep-th/9205109
| 727,347 |
The universal Witham hierarchy is considered from the point of view of
topological field theories. The $\tau$-function for this hierarchy is defined.
It is proved that the algebraic orbits of Whitham hierarchy can be identified
with various topological matter models coupled with topological gravity.
|
hep-th/9205110
| 727,347 |
Time does not obviously appear amongst the coordinates on the constrained
phase space of general relativity in the Hamiltonian formulation. Recent work
in finite-dimensional models claims that topological obstructions generically
make the global definition of time impossible. It is shown here that a time
coordinate can be globally defined on a constrained phase space by patching
together local time coordinates, just as coordinates are defined on
topologically non-trivial manifolds.
|
hep-th/9205112
| 727,347 |
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.
|
hep-ph/9205245
| 727,347 |
The $K=4$ fractional superstring Fock space is constructed in terms of
$\bZ_4$ parafermions and free bosons. The bosonization of the $\bZ_4$
parafermion theory and the generalized commutation relations satisfied by the
modes of various parafermion fields are reviewed. In this preliminary analysis,
we describe a Fock space which is simply a tensor product of $\bZ_4$
parafermion and free boson Fock spaces. It is larger than the Lorentz-covariant
Fock space indicated by the fractional superstring partition function. We
derive the form of the fractional superconformal algebra that may be used as
the constraint algebra for the physical states of the FSS. Issues concerning
the associativity, modings and braiding properties of the fractional
superconformal algebra are also discussed. The use of the constraint algebra to
obtain physical state conditions on the spectrum is illustrated by an
application to the massless fermions and bosons of the $K=4$ fractional
superstring. However, we fail to generalize these considerations to the massive
states. This means that the appropriate constraint algebra on the fractional
superstring Fock space remains to be found. Some possible ways of doing this
are discussed.
|
hep-th/9205113
| 727,347 |
We construct and study an N=3 supersymmetric Chern-Simons Higgs theory. This
theory is the maximally supersymmetric one containing the self-dual models with
a single gauge field and no gravity.
|
hep-th/9205115
| 727,348 |
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.
|
hep-ph/9205247
| 727,348 |
The conformal non-compact $SL(2,R)/U(1)$ coset model in two dimensions has
been recently shown to embody a nonlinear $\hat{W}_\infty$ current algebra,
consisting of currents of spin $\geq 2$ including the energy-momentum tensor.
In this letter we explicitly construct an infinite set of commuting quantum
$\hat{W}_\infty$ charges in the model with $k=1$. These commuting quantum
charges generate a set of infinitely many compatible flows (quantum KP flows),
which maintain the nonlinear $\hat{W}_\infty$ current algebra invariant.
|
hep-th/9205117
| 727,348 |
It is known that the 3d Chern-Simons interaction describes the scaling limit
of a quantum Hall system and predicts edge currents in a sample with boundary,
the currents generating a chiral $U(1)$ Kac-Moody algebra. It is no doubt also
recognized that in a somewhat similar way, the 4d $BF$ interaction (with $B$ a
two form, $dB$ the dual $^*j$ of the eletromagnetic current, and F the
electromagnetic field form) describes the scaling limit of a superconductor. We
show in this paper that there are edge excitations in this model as well for
manifolds with boundaries. They are the modes of a scalar field with invariance
under the group of diffeomorphisms (diffeos) of the bounding spatial
two-manifold. Not all of this group seem implementable by operators in quantum
theory, the implementable group being a subgroup of volume preserving diffeos.
The $BF$ system in this manner can lead to the $w_{1+\infty }$ algebra and its
variants. Lagrangians for fields on the bounding manifold which account for the
edge observables on quantization are also presented. They are the analogues of
the $1+1$ dimentional massless scalar field Lagrangian describing the edge
modes of an abelian Chern-Simons theory with a disk as the spatial manifold. We
argue that the addition of ``Maxwell'' terms constructed from $F\wedge ^*F$ and
$dB\wedge ^*dB$ do not affect the edge states, and that the augmented
Lagrangian has an infinite number of conserved charges- the aforementioned
scalar field modes- localized at the edges. This Lagrangian is known to
describe London equations and a massive vector field. A $(3+1)$ dimensional
generalization of the Hall effect involving vortices coupled to $B$ is also
proposed.
|
hep-th/9205116
| 727,348 |
A topological space $X$ is called $\Cal A$-real compact, if every algebra
homomorphism from $\Cal A$ to the reals is an evaluation at some point of $X$,
where $\Cal A$ is an algebra of continuous functions. Our main interest lies on
algebras of smooth functions. In \cite{AdR} it was shown that any separable
Banach space is smoothly real compact. Here we generalize this result to a huge
class of locally convex spaces including arbitrary products of separable
Fr\'echet spaces.
|
math/9206204
| 727,350 |
We reconsider the construction of solitons by dressing transformations in the
sine-Gordon model. We show that the $N$-soliton solutions are in the orbit of
the vacuum, and we identify the elements in the dressing group which allow us
to built the $N$-soliton solutions from the vacuum solution. The dressed
$\tau$-functions can be computed in two different ways~: either using adjoint
actions in the affine Lie algebra $\hat {sl_2}$, and this gives the relation
with the B\"acklund transformations, or using the level one representations of
the affine Lie algebra $\widehat{sl_2}$, and this directly gives the formulae
for the $\tau$-functions in terms of vertex operators.
|
hep-th/9206002
| 727,350 |
We study the thermodynamic properties of a family of integrable 1D spin chain
hamiltonians associated with quantum groups at roots of unity. These
hamiltonians depend for each primitive root of unit on a parameter $s$ which
plays the role of a continuous spin. The model exhibits ferrimagnetism even
though the interaction involved is between nearest neighbors. The latter
phenomenon is interpreted as a genuine quantum group effect with no
``classical" analog. The discussion of conformal properties is given.
|
hep-th/9206001
| 727,350 |
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.
|
hep-ph/9206201
| 727,350 |
Using exact expressions for the Ising form factors, we give a new very simple
proof that the spin-spin and disorder-disorder correlation functions are
governed by the Painlev\'e III non linear differential equation. We also show
that the generating function of the correlation functions of the descendents of
the spin and disorder operators is a $N$-soliton, $N\to\infty$, $\tau$-function
of the sinh-Gordon hierarchy. We discuss a relation of our approach to
isomonodromy deformation problems, as well as further possible generalizations.
|
hep-th/9206003
| 727,350 |
We establish the phase diagram of three--dimensional quantum gravity coupled
to Ising matter. We find that in the negative curvature phase of the quantum
gravity there is no disordered phase for ferromagnetic Ising matter because the
coordination number of the sites diverges. In the positive curvature phase of
the quantum gravity there is evidence for two spin phases with a first order
transition between them.
|
hep-lat/9205029
| 727,350 |
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.
|
hep-ph/9206202
| 727,350 |
We investigate the possibility of false vacuum decay in $N=1$ supergravity
theories. By establishing a Bogomol'nyi bound for the energy density stored in
the domain wall of the $O(4)$ invariant bubble, we show that supersymmetric
vacua remain absolutely stable against false vacuum decay into another
supersymmetric vacuum. This conforms with and completes the previous
perturbative analysis of Weinberg. Implications for dynamical supersymmetry
breaking and decompactification instabilities in superstring theory are
discussed. In addition, we show that there are no compact static spherical
domain walls.
|
hep-th/9206004
| 727,350 |
In the framework of noncompact lattice QED with light fermions, we derive the
functional dependence of the average energy per plaquette on the bare
parameters using block-spin Renormalization Group arguments and assuming that
the renormalized coupling vanishes. Our numerical results for this quantity in
$8^4$ and $10^4$ lattices show evidence for triviality in the weak coupling
phase and point to a non vanishing value for the renormalized coupling constant
in the strong coupling phase.
|
hep-lat/9205030
| 727,350 |
An algebraic rule is presented for computing expectation values of products
of local nonabelian charge operators for fermions coupled to an external vector
potential in $3+1$ space-time dimensions. The vacuum expectation value of a
product of four operators is closely related to a cyclic cocycle in
noncommutative geometry of Alain Connes. The relevant representation of the
current is constructed using Kirillov's method of coadjoint orbits.
|
hep-th/9206005
| 727,350 |
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.
|
hep-ph/9206203
| 727,350 |
Using a Hamiltonian approach to gauged WZW models, we present a general
method for computing the conformally exact metric and dilaton, to all orders in
the $1/k$ expansion, for any bosonic, heterotic, or type-II superstring model
based on a coset $G/H$. We prove the following relations: (i) For type-II
superstrings the conformally exact metric and dilaton are identical to those of
the non-supersymmetric {\it semi-classical} bosonic model except for an overall
renormalization of the metric obtained by $k\to k- g$. (ii) The exact
expressions for the heterotic superstring are derived from their exact bosonic
string counterparts by shifting the central extension $k\to 2k-h$ (but an
overall factor $(k-g)$ remains unshifted). (iii) The combination
$e^\Phi\sqrt{-G}$ is independent of $k$ and therefore can be computed in lowest
order perturbation theory as required by the correct formulation of a
conformally invariant path integral measure. The general formalism is applied
to the coset models $SO(d-1,2)_{-k}/SO(d-1,1)_{-k}$ that are relevant for
string theory on curved spacetime. Explicit expressions for the conformally
exact metric and dilaton for the cases $d=2,3,4$ are given. In the
semiclassical limit $(k\to \infty)$ our results agree with those obtained with
the Lagrangian method up to 1-loop in perturbation theory.
|
hep-th/9206006
| 727,351 |
We study quantum Chern-Simons theory as the large mass limit of the limit
$D\to 3$ of dimensionally regularized topologically massive Yang-Mills theory.
This approach can also be interpreted as a BRS-invariant hybrid regularization
of Chern-Simons theory, consisting of a higher-covariant derivative Yang-Mills
term plus dimensional regularization. Working in the Landau gauge, we compute
radiative corrections up to second order in perturbation theory and show that
there is no two-loop correction to the one-loop shift $k\rightarrow k+
c_{\scriptscriptstyle V},\,\,k$ being the bare Chern-Simons parameter. In
passing we also prove by explicit computation that topologically massive
Yang-Mills theory is UV finite.
|
hep-th/9206007
| 727,351 |
We study the modular invariance of $N=2$ superconformal $SU(1,1)$ models. By
decomposing the characters of Kazama-Suzuki model $SU(3)/(SU(2)\times U(1))$
into an infinite sum of the characters of $(SU(1,1)/U(1))\times U(1)$ we
construct modular invariant partition functions of $(SU(1,1)/U(1))\times U(1)$.
|
hep-th/9206008
| 727,351 |
We have studied the quantum Liouville theory on the Riemann sphere with n>3
punctures. While considering the theory on the Riemann surfaces with n=4
punctures, the quantum theory near an arbitrary but fixed puncture can be
obtained via canonical quantization and an extra symmetry is explored. While
considering more than four distinguished punctures, we have found the exchange
relations of the monodromy parameters from which we can get a reasonable
quantum theory.
|
hep-th/9206009
| 727,351 |
QCD with eight flavors is studied on $16^3\times N_t$ lattices with $N_t=4$,
6, 8, 16 and 32, a dynamical quark mass $ma=0.015$ and lattice coupling
$\beta=6/g^2$ between 4.5 and 5.0. For $N_t=16$ and 32, hadron masses and
screening lengths are computed for a variety of valence quark masses. The
previously observed, strong, first-order transition for $N_t=4$, 6 and 8 is
seen, for $N_t=16$, to become a $\beta$-independent, zero-temperature
transition characterized by a factor of $\approx 3$ change in lattice scale.
This strong, first-order transition restores chiral symmetry, at least for
$N_t=4$, 6 and 8, producing a chirally symmetric, weak-coupling phase. However,
as $N_t$ increases to 16, the chiral symmetry properties of the weak-coupling
side of the zero-temperature transition are unclear and offer a hint of a
normal, finite-temperature, chiral symmetry breaking transition in the
weak-coupling phase.
|
hep-lat/9206001
| 727,351 |
The group PGL(3) of linear transformations of the projective plane acts
naturally on the projective space parametrizing curves of a given degree. In
this note we begin the study of the orbits of smooth curves under this action:
we construct a resolution of the closure of the orbit of a given curve, and we
use it to compute its degree. This turns out to depend only on the degree of
the curve, the order of its automorphism group, and on the number and type of
its flexes. This paper will appear on the Journal of Algebraic Geometry.
|
alg-geom/9206001
| 727,351 |
A simple model that describes traffic flow in two dimensions is studied. A
sharp {\it jamming transition } is found that separates between the low density
dynamical phase in which all cars move at maximal speed and the high density
jammed phase in which they are all stuck. Self organization effects in both
phases are studied and discussed.
|
cond-mat/9206001
| 727,351 |
We construct the Zamolodchikov's c-function for the Chiral Gross-Neveu Model
up to two loops. We show that the c-function interpolates between the two known
critical points of the theory, it is stationary at them and it decreases with
the running coupling constant. In particular one can infer the non-existence of
additional critical points in the region under investigation.
|
hep-th/9206011
| 727,351 |
Two dimensional charged black hole solution is obtained by implementing an
$O(2,2)$ transformation on the three dimensional black string solution. Two
different monopole backgrounds in five dimensions are related through an
$O(2,2)$ transformation. It has been shown in these examples that the
particular $O(2,2)$ transformation corresponds to duality transformation.
|
hep-th/9206017
| 727,351 |
We investigate the evaluation of the Dirac index using symplectic geometry in
the loop space of the corresponding supersymmetric quantum mechanical model. In
particular, we find that if we impose a simple first class constraint, we can
evaluate the Callias index of an odd dimensional Dirac operator directly from
the quantum mechanical model which yields the Atiyah-Singer index of an even
dimensional Dirac operator in one more dimension. The effective action obtained
by BRST quantization of this constrained system can be interpreted in terms of
loop space symplectic geometry, and the corresponding path integral for the
index can be evaluated exactly using the recently developed localization
techniques.
|
hep-th/9206010
| 727,351 |
The one-dimensional attractive lattice fermion gas equivalent to the
Heisenberg-Ising spin 1/2 chain is studied for a ring geometry threaded by
magnetic flux. We find that for charged fermions having interaction strength
$\Delta=\cos(\pi / p)$ with $p$ {\it noninteger}, the adiabatic ground state is
periodic in the magnetic flux threading the chain, with period 2 flux quanta,
as found by Shastry and Sutherland for the repulsive case. We find that, at
particular values of the threading field, a sequence of initially zero-energy
bound states form at the Fermi surface during the adiabatic process, the
largest containing $[p]$ (the integer part of $p$) fermions. This largest bound
state moves around to the other Fermi point and sequentially unbinds. We find
Berry's Phase for the whole process to be $[p] \pi$. For $p$ {\it integer}, as
$\Phi$ increases, eventually all the particles in the system go into bound
states of size $[p]$. The period in this case is of order the size of the
system.
|
cond-mat/9206002
| 727,352 |
We present model predictions for the spectrum of $CP^{N-1}$ in a periodic box
and use them to interpret the strong finite size effects observed in lattice
simulations at medium values of $N$. The asymptotic scaling behaviour of
alternative lattice actions is discussed along with some aspects of multigrid
algorithm efficiency.
|
hep-lat/9206003
| 727,352 |
We study a simple 2-d model representing two fields with different mass and a
3-point coupling term. The phase shift in the resonating 2-particle channel is
determined from the energy spectrum obtained in Monte Carlo simulations on
finite lattices. Masses and wave function renormalization constants of the
fields as well as mass and width of the resonance are determined and discussed.
The representation of scattering states in terms of the considered operators is
analysed.
|
hep-lat/9206004
| 727,352 |
We describe the quasitriangular structure (universal $R$-matrix) on the
non-standard quantum group $U_q(H_1,H_2,X^\pm)$ associated to the
Alexander-Conway matrix solution of the Yang-Baxter equation. We show that this
Hopf algebra is connected with the super-Hopf algebra $U_qgl(1|1)$ by a general
process of superization.
|
hep-th/9206013
| 727,352 |
We present a new method for regularizing chiral theories on the lattice. The
arbitrariness in the regularization is used in order to decouple massless
replica fermions. A continuum limit with only one fermion is obtained in
perturbation theory and a Golterman-Petcher like symmetry related to the
decoupling of the replicas in the non-perturbative regime is identified. In the
case of Chiral Gauge Theories gauge invariance is broken at the level of the
regularization, so our approach shares many of the characteristics of the Rome
approach.
|
hep-lat/9206005
| 727,352 |
We propose and study at large N a new lattice gauge model , in which the
Yang-Mills interaction is induced by the heavy scalar field in adjoint
representation. At any dimension of space and any $ N $ the gauge fields can be
integrated out yielding an effective field theory for the gauge invariant
scalar field, corresponding to eigenvalues of the initial matrix field. This
field develops the vacuum average, the fluctuations of which describe the
elementary excitations of our gauge theory. At $N= \infty $ we find two phases
of the model, with asymptotic freedom corresponding to the strong coupling
phase (if there are no phase transitions at some critical $N$). We could not
solve the model in this phase, but in the weak coupling phase we have derived
exact nonlinear integral equations for the vacuum average and for the scalar
excitation spectrum. Presumably the strong coupling equations can be derived by
the same method.
|
hep-th/9206015
| 727,352 |
A new gauge fixing condition is discussed, which is (lattice) rotation
invariant, has the `smoothness' properties of the Landau gauge but can be
efficiently computed and is unambiguous for almost all lattice gauge field
configurations.
|
hep-lat/9206006
| 727,352 |
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.
|
hep-ph/9206205
| 727,352 |
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.
|
hep-ph/9206206
| 727,352 |
A short and elementary proof, and a finite-form generalization, are given of
Jacobi's formula for the number of ways of writing an integer as a sum of four
squares (that implies Lagrange's famous 1777 theorem.)
|
math/9206203
| 727,352 |
We introduce a lattice fermion-Higgs model with one component `reduced
staggered' fermions. In order to use the fermion field as efficiently as
possible we couple the two {\em staggered} flavors to the O(4) Higgs field
leading to a model with only one SU(2) doublet in the scaling region. The
number of fermions is doubled in a numerical investigation of the model with
the hybrid Monte Carlo algorithm. We present results for the phase diagram,
particle masses and renormalized couplings on lattices ranging in size from
$6^3 24$ to $16^3 24$.
|
hep-lat/9206008
| 727,352 |
Classical solutions of equations of motion in low energy effective field
theory, describing fundamental charged heterotic string, are found. These
solutions automatically carry an electric current equal to the charge per unit
length, and hence are accompanied by both, electric and magnetic fields. Force
between two parallel strings vanish due to cancellation between electric and
magnetic forces, and also between graviton, dilaton, and antisymmetric tensor
field induced forces. Multi-string solutions describing configuration of
parallel strings are also found. Finally, the solutions are shown to possess
partially broken space-time supersymmetry.
|
hep-th/9206016
| 727,352 |
We find the discrete states of the c=1 string in the light-cone gauge of
Polyakov. When the state space of the gravitational sector of the theory is
taken to be the irreducible representations of the SL(2,R) current algebra, the
cohomology of the theory is NOT the same as that in the conformal gauge. In
particular, states with ghost numbers up to 4 appear. However, after taking the
space of the theory to be the Fock space of the Wakimoto free-field
representation of the SL(2,R), the light-cone and conformal gauges are
equivalent. This supports the contention that the discrete states of the theory
are physical. We point out that the natural states in the theory do not satisfy
the KPZ constraints.
|
hep-th/9206014
| 727,352 |
Reply to Comments on ``Asymptotic Estimate of the {\it n}-Loop QCD
Contribution to the Total $e^{+}e^{-}$ Annihilation Cross Section''
|
hep-ph/9206207
| 727,352 |
The Fortuin-Kasteleyn mapping between the Ising model and the site-bond
correlated percolation model is shown to be only one of an infinite class of
exact mappings. These new cluster representations are a result of
"renormalized" percolation rules correlated to entire blocks of spins. For
example these rules allow for percolation on "virtual" bonds between spins not
present in the underlying Hamiltonian. As a consequence we can define new
random cluster theories each with its own Monte Carlo cluster dynamics that
exactly reproduce the Ising model. By tuning parameters on the critical
percolation surface, it is demonstrated numerically that cluster algorithms can
be formulated for the 2-d and 3-d Ising model that have smaller
autocorrelations than the original Swendsen-Wang algorithm.
|
hep-lat/9206007
| 727,353 |
We present a technique which permits the calculation of two-point functions
of operators containing one heavy quark and an arbitrary number of light quarks
as analytic functions of the heavy-quark mass. It is based on the standard
Jacobi linear solver used for the calculation of quark propagators. Results for
the heavy-light pseudoscalar and vector meson masses are obtained on 16^3x48
lattices at beta = 6.2 using the Wilson fermion action, and agree with
published data. The incorporation of smeared operators and $O(a)$-improved
actions presents no problems.
|
hep-lat/9206009
| 727,353 |
We classify smooth surfaces whose higher cohomologies of i-forms for all i
vanish. We show that if such a surface is not affine, then it has essentially
two possibilities.
|
alg-geom/9206003
| 727,353 |
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.
|
hep-ph/9206208
| 727,353 |
Campbell et al. demonstrated the existence of axion ``hair'' for Kerr black
holes due to the non-trivial Lorentz Chern-Simons term and calculated it
explicitly for the case of slow rotation. Here we consider the dilaton coupling
to the axion field strength, consistent with low energy string theory and
calculate the dilaton ``hair'' arising from this specific axion source.
|
hep-th/9206018
| 727,353 |
We consider the BRST and superconformal properties of the ghost action of 2-D
supergravity. Using the background spin structure on the worldsheet, we show
that this action can be transformed by canonical field transformations to reach
other conformal models such as the 2-D topological gravity or the chiral models
for which the gauge variation of the action reproduces the left or right
conformal anomaly. Our method consists in using the gravitino and its ghost as
fundamental blocks to build fields with different conformal weights and
statistics. This indicates in particular that the twisting of a conformal model
into another one can be classically interpreted as a change of "field
representation" of the superconformal symmetry.
|
hep-th/9206019
| 727,353 |
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.
|
hep-ph/9206209
| 727,353 |
There is a large mathematical literature on classical mechanics and field
theory, especially on the relationship to symplectic geometry. One might think
that the classical Chern-Simons theory, which is topological and so has
vanishing hamiltonian, is completely trivial. However, this theory exhibits
interesting geometry that is usually absent from ordinary field theories. (The
same is true on the quantum level; topological quantum field theories exhibit
geometric properties not usually seen in ordinary quantum field theories, and
they lack analytic properties which are usually seen.) In this paper we
carefully develop this geometry. Of particular interest are the line bundles
with connection over the moduli space of flat connections on a 2-manifold. We
extend the usual theory to cover 2-manifolds with boundary. We carefully
develop ``gluing laws'' in all of our constructions, including the line bundle
with connection over moduli space. The corresponding quantum gluing laws are
fundamental. Part 1 covers connected and simply connected gauge groups; Part 2
will cover arbitrary compact Lie groups.
|
hep-th/9206021
| 727,353 |
The properties of a string-inspired two-dimensional theory of gravity are
studied. The post-Newtonian and weak-field approximations, `stellar' structure
and cosmological solutions of this theory are developed. Some qualitative
similarities to general relativity are found, but there are important
differences.
|
hep-th/9206022
| 727,353 |
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.
|
hep-ph/9206210
| 727,353 |
The algebra dual to Woronowicz's deformation of the 2-\-di\-men\-sion\-al
Euclidean group is constructed. The same algebra is obtained from $SU_{q}(2)$
via contraction on both the group and algebra levels.
|
hep-th/9206024
| 727,353 |
A truncation of string field theory is compared with the duality invariant
effective action of $D=4, N=4$ heterotic strings to cubic order. The three
string vertex must satisfy a set of compatibility conditions. Any cyclic three
string vertex is compatible with the $D=4, N=4$ effective field theory. The
effective actions may be useful in understanding the non--polynomial structure
and the underlying symmetry of covariant closed string field theory, and in
addressing issues of background independence. We also discuss the effective
action and string field theory of the $N=2$ string.
|
hep-th/9206023
| 727,353 |
The model proposed by Eichten and Preskill for obtaining theories with chiral
fermions from the lattice is shown to undergo spontaneous symmetry breaking. In
addition, the fermions appear to be Dirac-like everywhere in the phase diagram
with no room for undoubled Weyl fermions. The phase diagram of a closely
related Higgs-Yukawa model is similar to that of the Smit--Swift model, which
also does not give rise to chiral fermions. These results cast serious doubts
on the original scenario for the emergence of chiral fermions.
|
hep-lat/9206010
| 727,353 |
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.
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hep-ph/9206211
| 727,353 |
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