701 research outputs found
On the consistent solution of the gap--equation for spontaneously broken -theory
We present a self--consistent solution of the finite temperature
gap--equation for theory beyond the Hartree-Fock approximation
using a composite operator effective action. We find that in a spontaneously
broken theory not only the so--called daisy and superdaisy graphs contribute to
the resummed mass, but also resummed non--local diagrams are of the same order,
thus altering the effective mass for small values of the latter.Comment: 15 pages of revtex + 3 uuencoded postscript figures, ENSLAPP A-488/9
Convergence of the Optimized Delta Expansion for the Connected Vacuum Amplitude: Zero Dimensions
Recent proofs of the convergence of the linear delta expansion in zero and in
one dimensions have been limited to the analogue of the vacuum generating
functional in field theory. In zero dimensions it was shown that with an
appropriate, -dependent, choice of an optimizing parameter \l, which is an
important feature of the method, the sequence of approximants tends to
with an error proportional to . In the present paper we
establish the convergence of the linear delta expansion for the connected
vacuum function . We show that with the same choice of \l the
corresponding sequence tends to with an error proportional to . The rate of convergence of the latter sequence is governed by
the positions of the zeros of .Comment: 20 pages, LaTeX, Imperial/TP/92-93/5
MiniBooNE
The physics motivations, design, and status of the Booster Neutrino
Experiment at Fermilab, MiniBooNE, are briefly discussed. Particular emphasis
is given on the ongoing preparatory work that is needed for the MiniBooNE muon
neutrino to electron neutrino oscillation appearance search. This search aims
to confirm or refute in a definitive and independent way the evidence for
neutrino oscillations reported by the LSND experiment.Comment: 3 pages, no figures, to appear in the proceedings of the 9th
International Conference on Astroparticle and Underground Physics (TAUP
2005), Zaragoza, Spain, 10-14 Sep 200
MiniBooNE Oscillation Results 2011
The MiniBooNE neutrino oscillation search experiment at Fermilab has recently
updated results from a search for
oscillations, using a data sample corresponding to
protons on target in anti-neutrino mode. This high statistics result represent
an increase in statistics of 52% compared to result published in 2010. An
excess of 57.7 28.5 events is observed in the energy range 200 MeV 3000 MeV. The data favor LSND-like
oscillations over a background only hypothesis at 91.1% confidence level in the
energy range 475 3000 MeV.Comment: 4 pages, 6 figures, talk given at NuFact 2011, XIIIth
InternationalWorkshop on Neutrino Factories, Super beams and Beta beams,
CERN/UNIGE, Geneva, Switzerland, August 1-6, 201
The Nucleon-Nucleon Interaction in a Chiral Constituent Quark Model
We study the short-range nucleon-nucleon interaction in a chiral constituent
quark model by diagonalizing a Hamiltonian comprising a linear confinement and
a Goldstone boson exchange interaction between quarks. The six-quark harmonic
oscillator basis contains up to two excitation quanta. We show that the highly
dominant configuration is due to its specific
flavour-spin symmetry. Using the Born-Oppenheimer approximation we find a
strong effective repulsion at zero separation between nucleons in both
and channels. The symmetry structure of the highly dominant
configuration implies the existence of a node in the S-wave relative motion
wave function at short distances. The amplitude of the oscillation of the wave
function at short range will be however strongly suppressed. We discuss the
mechanism leading to the effective short-range repulsion within the chiral
constituent quark model as compared to that related with the one-gluon exchange
interaction.Comment: 31 pages, LaTe
A new method for the solution of the Schrodinger equation
We present a new method for the solution of the Schrodinger equation
applicable to problems of non-perturbative nature. The method works by
identifying three different scales in the problem, which then are treated
independently: An asymptotic scale, which depends uniquely on the form of the
potential at large distances; an intermediate scale, still characterized by an
exponential decay of the wave function and, finally, a short distance scale, in
which the wave function is sizable. The key feature of our method is the
introduction of an arbitrary parameter in the last two scales, which is then
used to optimize a perturbative expansion in a suitable parameter. We apply the
method to the quantum anharmonic oscillator and find excellent results.Comment: 4 pages, 4 figures, RevTex
On the Divergence of Perturbation Theory. Steps Towards a Convergent Series
The mechanism underlying the divergence of perturbation theory is exposed.
This is done through a detailed study of the violation of the hypothesis of the
Dominated Convergence Theorem of Lebesgue using familiar techniques of Quantum
Field Theory. That theorem governs the validity (or lack of it) of the formal
manipulations done to generate the perturbative series in the functional
integral formalism. The aspects of the perturbative series that need to be
modified to obtain a convergent series are presented. Useful tools for a
practical implementation of these modifications are developed. Some resummation
methods are analyzed in the light of the above mentioned mechanism.Comment: 42 pages, Latex, 4 figure
Synaptogyrin-3 mediates presynaptic dysfunction induced by Tau
Synaptic dysfunction is an early pathological feature of neurodegenerative diseases associated with Tau, including Alzheimer's disease. Interfering with early synaptic dysfunction may be therapeutically beneficial to prevent cognitive decline and disease progression, but the mechanisms underlying synaptic defects associated with Tau are unclear. In disease conditions, Tau mislocalizes into pre- and postsynaptic compartments; here we show that, under pathological conditions, Tau binds to presynaptic vesicles in Alzheimer's disease patient brain. We define that the binding of Tau to synaptic vesicles is mediated by the transmembrane vesicle protein Synaptogyrin-3. In fly and mouse models of Tauopathy, reduction of Synaptogyrin-3 prevents the association of presynaptic Tau with vesicles, alleviates Tau-induced defects in vesicle mobility, and restores neurotransmitter release. This work therefore identifies Synaptogyrin-3 as the binding partner of Tau on synaptic vesicles, revealing a new presynapse-specific Tau interactor, which may contribute to early synaptic dysfunction in neurodegenerative diseases associated with Tau
A Letter of Intent to Build a MiniBooNE Near Detector: BooNE
There is accumulating evidence for a difference between neutrino and
antineutrino oscillations at the eV scale. The MiniBooNE
experiment observes an unexplained excess of electron-like events at low
energies in neutrino mode, which may be due, for example, to either a neutral
current radiative interaction, sterile neutrino decay, or to neutrino
oscillations involving sterile neutrinos and which may be related to the LSND
signal. No excess of electron-like events (), however, is
observed so far at low energies in antineutrino mode. Furthermore, global 3+1
and 3+2 sterile neutrino fits to the world neutrino and antineutrino data
suggest a difference between neutrinos and antineutrinos with significant
() disappearance. In order to
test whether the low-energy excess is due to neutrino oscillations and whether
there is a difference between and disappearance, we
propose building a second MiniBooNE detector at (or moving the existing
MiniBooNE detector to) a distance of m from the Booster Neutrino
Beam (BNB) production target. With identical detectors at different distances,
most of the systematic errors will cancel when taking a ratio of events in the
two detectors, as the neutrino flux varies as to a calculable
approximation. This will allow sensitive tests of oscillations for both
and appearance and and disappearance.
Furthermore, a comparison between oscillations in neutrino mode and
antineutrino mode will allow a sensitive search for CP and CPT violation in the
lepton sector at short baseline ( eV).Comment: 43 pages, 40 figure
A Light Sterile Neutrino in the TopFlavor Model
A scenario based on the TopFlavor model is presented to explain the origin of
a light sterile neutrino as indicated by all combined neutrino oscillation
experiments. The model is phenomenologically well motivated and compatible with
all available low-energy data. The derived nuetrino mass matrix can
qualitatively explain the observed hierarchy in the neutrino mass splittings as
indicated by the neutrino oscillation data. Numerical results are obtained for
special cases.Comment: Plain Latex file, 12 page
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