224 research outputs found
Differential analysis of matrix convex functions
We analyze matrix convex functions of a fixed order defined on a real
interval by differential methods as opposed to the characterization in terms of
divided differences given by Kraus. We obtain for each order conditions for
matrix convexity which are necessary and locally sufficient, and they allow us
to prove the existence of gaps between classes of matrix convex functions of
successive orders, and to give explicit examples of the type of functions
contained in each of these gaps. The given conditions are shown to be also
globally sufficient for matrix convexity of order two. We finally introduce a
fractional transformation which connects the set of matrix monotone functions
of each order n with the set of matrix convex functions of order n+1
A simple proof of Hardy-Lieb-Thirring inequalities
We give a short and unified proof of Hardy-Lieb-Thirring inequalities for
moments of eigenvalues of fractional Schroedinger operators. The proof covers
the optimal parameter range. It is based on a recent inequality by Solovej,
Soerensen, and Spitzer. Moreover, we prove that any non-magnetic Lieb-Thirring
inequality implies a magnetic Lieb-Thirring inequality (with possibly a larger
constant).Comment: 12 page
Production of Heavy Selectrons in Electron-Photon Collisions
We study the production and decay of heavy selectrons in the electron-photon
mode of a linear collider of the next generation. The standard model
backgrounds can be substantially reduced by appropriate kinematical cuts. As a
consequence, selectrons far heavier than the kinematical threshold for pair
production are shown to be easily discoverable for large portions of the
supersymmetry parameter space. We also describe a model-independent kinematical
measurement of the mass of the lightest neutralino.Comment: 20 pages, 7 LaTeX figures Postscript version available at
ftp://gluon.hep.physik.uni-muenchen.de/preprints/mpi9486.p
DELETION OF THE HERPES SIMPLEX VIRUS 1 INTERNAL REPEAT SEQUENCES AFFECTS PATHOGENICITY IN THE MOUSE
ABSTRACT We have isolated three different herpes simplex virus 1 (HSV-1) recombinant viruses, each frozen in either the P (prototype), IS (inversion of S component), or ILS (inversion of both components) genome arrangement. Common to all three recombinant viruses is the deletion of approximately 14 kilobases (kb) of viral DNA sequences representing greater than 95% of the internal repeat sequences and the insertion of a 9.6 kb mini-Mu genome containing a functional thymidine kinase gene. No unique DNA sequences were deleted from the viral genomes. Analyses of growth curves of the wild-type and recombinant viruses in cell culture has revealed that the recombinants grow somewhat more slowly, producing final titers within 1.5 logs of wild-type HSV-1(F). There is no discernible difference in plaque size or plaque morphology between the recombinant and wild type strains. Analysis of the recombinant viruses in mice reveals the following: I), the recombinant viruses are essentially avirulent, exhibiting drastically increased LD50 values as compared to the wild-type strain by intracerebral injection; ii), the recombinant viruses are not neuroinvasive in that they do not spread from the cornea to sensory ganglion; iii), the recombinant viruses exhibit minimal local replication both in the corneas of infected mice and in the brains of mice inoculated by intracerebral injection; and iv), the recombinant viruses do not establish a reactivable latent infection in the trigeminal ganglion following either intracerebral inoculation or inoculation of scarified corneas. These properties suggest a unique pattern of pathogenesis for HSV mutants in the mouse model
Mesons as qbar-q Bound States from Euclidean 2-Point Correlators in the Bethe-Salpeter Approach
We investigate the 2-point correlation function for the vector current. The
gluons provide dressings for both the quark self energy as well as the vector
vertex function, which are described consistently by the rainbow
Dyson-Schwinger equation and the inhomogeneous ladder Bethe-Salpeter equation.
The form of the gluon propagator at low momenta is modeled by a 2-parameter
ansatz fitting the weak pion decay constant. The quarks are confined in the
sense that the quark propagator does not have a pole at timelike momenta. We
determine the ground state mass in the vector channel from the Euclidean time
Fourier transform of the correlator, which has an exponential falloff at large
times. The ground state mass lies around 590 MeV and is almost independent of
the model form for the gluon propagator. This method allows us to stay in
Euclidean space and to avoid analytic continuation of the quark or gluon
propagators into the timelike region.Comment: 21 pages (REVTEX), 8 Postscript figure
b -> s gamma in the left-right supersymmetric model
The rare decay is studied in the left-right supersymmetric
model. We give explicit expressions for all the amplitudes associated with the
supersymmetric contributions coming from gluinos, charginos and neutralinos in
the model to one-loop level. The branching ratio is enhanced significantly
compared to the standard model and minimal supersymmetric standard model values
by contributions from the right-handed gaugino and squark sector. We give
numerical results coming from the leading order contributions. If the only
source of flavor violation comes from the CKM matrix, we constrain the scalar
fermion-gaugino sector. If intergenerational mixings are allowed in the squark
mass matrix, we constrain such supersymmetric sources of flavor violation. The
decay sets constraints on the parameters of the model and
provides distinguishing signs from other supersymmetric scenarios.Comment: 12 figure
RPA-Approach to the Excitations of the Nucleon, Part II: Phenomenology
The tensor-RPA approach developed previously in part I is applied to the
Nambu-Jona-Lasinio (NJL) model. As a first step we investigate the structure of
Dirac-Hartree-Fock solutions for a rotationally and isospin invariant
ground-state density. Whereas vacuum properties can be reproduced, no solitonic
configuration for a system with unit baryon number is found. We then solve the
tensor-RPA equation employing simple models of the nucleon ground state. In
general the ph interaction effects a decrease of the excited states to lower
energies. Due to an enhanced level density at low energies the obtained spectra
cannot be matched with the experimental data when a standard MIT-bag
configuration is used. However, when the size of the nucleon quark core is
reduced to approximately 0.3 fm a fair description of the baryon spectrum in
the positive-parity channel is achieved. For this purpose the residual
interaction turns out to be crucial and leads to a significant improvement
compared with the mean-field spectra.Comment: 33 pages, Latex, 9 Postscpript figures, section on the excited states
has been completely rewritten after error was detected, results are now much
more encouragin
Quark structure of pseudoscalar mesons
I review to which extent the properties of pseudoscalar mesons can be
understood in terms of the underlying quark (and eventually gluon) structure.
Special emphasis is put on the progress in our understanding of eta-eta'
mixing. Process-independent mixing parameters are defined, and relations
between different bases and conventions are studied. Both, the low-energy
description in the framework of Chiral Perturbation Theory and the high-energy
application in terms of light-cone wave functions for partonic Fock states, are
considered. A thorough discussion of theoretical and phenomenological
consequences of the mixing approach will be given. Finally, I will discuss
mixing with other states pi^0, eta(c), ...).Comment: 48 pages, 7 figures, using epsfig.st
Compton Scattering by a Pion and off--Shell Effects
We consider Compton scattering by a pion in the framework of chiral
perturbation theory. We investigate off--shell effects in the s-- and
u--channel pole diagrams. For that purpose we perform a field transformation
which, in comparison with the standard Gasser and Leutwyler Lagrangian,
generates additional terms at order proportional to the lowest--order
equation of motion. As a result of the equivalence theorem the two Lagrangians
predict the same Compton scattering S--matrix even though they generate
different off--shell form factors. We conclude that off--shell effects are not
only model--dependent but also representation--dependent.Comment: 13 pages in LaTeX, using RevTex macro, TRIUMF preprint TRI-PP-94-6
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