3,804 research outputs found
Quantum Hall Transition in the Classical Limit
We study the quantum Hall transition using the density-density correlation
function. We show that in the limit h->0 the electron density moves along the
percolating trajectories, undergoing normal diffusion. The localization
exponent coincides with its percolation value \nu=4/3. The framework provides a
natural way to study the renormalization group flow from percolation to quantum
Hall transition. We also confirm numerically that the critical conductivity of
a classical limit of quantum Hall transition is \sigma_{xx} = \sqrt{3}/4.Comment: 8 pages, 4 figures; substantial changes include the critical
conductivity calculatio
Oscillating Casimir force between impurities in one-dimensional Fermi liquids
We study the interaction of two localized impurities in a repulsive
one-dimensional Fermi liquid via bosonization. In a previous paper [Phys. Rev.
A 72, 023616 (2005)], it was shown that at distances much larger than the
interparticle spacing the impurities interact through a Casimir-type force
mediated by the zero sound phonons of the underlying quantum liquid. Here we
extend these results and show that the strength and sign of this Casimir
interaction depend sensitively on the impurities separation. These oscillations
in the Casimir interaction have the same period as Friedel oscillations. Their
maxima correspond to tunneling resonances tuned by the impurities separation.Comment: This paper is a continuation of Phys. Rev. A 72, 023616 (2005). v2:
two appendix adde
Predictions from the Fritzsch-Type Lepton Mass Matrices
We revisit the Fritzsch-type lepton mass matrix models confronted with new
experiments for neutrino mixings. It is shown that the model is viable and
leads to a rather narrow range of free parameters. Using empirical mixing
information between and , and between and
, it is predicted that the mixing angle between and
is in the range , consistent with the CHOOZ experiment and
the lightest neutrino mass is eV. The range of the
effective mass measured in double beta decay is eV.Comment: Latex file with 13 pages, 6 eps file
Radiative Neutrino Mass in Type III Seesaw Model
The simplest type III seesaw model as originally proposed introduces one
lepton triplet. It thus contains four active neutrinos, two massive and two
massless at tree level. We determine the radiative masses that the latter
receive first at two loops. The masses are generally so tiny that they are
definitely excluded by the oscillation data, if the heavy leptons are not very
heavy, say, within the reach of LHC. To accommodate the data on masses, the
seesaw scale must be as large as the scale of grand unification. This indicates
that the most economical type III model would entail no new physics at low
energies beyond the tiny neutrino masses.Comment: 21 pages, 1 figure; v2: added 3 sentences in sec 4 for
clarifications, version published on 7 Apr 2009 in PR D79, 073003 (2009
Radiative and flavor-violating transitions of leptons from interactions with color-octet particles
It has been recently proposed that neutrino mass could originate from Yukawa
interactions of leptons with new colored particles. This raises the interesting
possibility of testing mass generation through copious production of those
particles at hadron colliders. A realistic assessment of it however should take
into account how large those interactions could be from available precision
results. In this work we make a systematic analysis to the flavor structure in
Yukawa couplings, provide a convenient parametrization to it, and investigate
the rare radiative and pure leptonic decays of the muon and tau leptons. For
general values of parameters the muon decays set stringent constraints on the
couplings, and all rare tau decays are far below the current experimental
sensitivity. However, there is room in parameter space in which the muon decays
could be significantly suppressed by destructive interference between colored
particles without generically reducing the couplings themselves. This is also
the region of parameters that is relevant to collider physics. We show that for
this part of parameter space some tau decays can reach or are close to the
current level of precision.Comment: 20 pages, 7 figure
Definition of the role of contemporary surgical management in cisternal and parenchymatous cysticercosis cerebri
Journal ArticleWith increasing immigration from endemic regions, the incidence of neurocysticercosis in North America is rising. This retrospective study was undertaken to examine the role of surgery in those cases presenting with large cystic parenchymal and cisternal lesions in the current era of anthelminthic agents administered orally. A total of 237 patients presented with newly diagnosed neurocysticercosis to our institution over a recent 5-year period (mean age. 31.2 years). Among those who presented with cystic mass lesions predominantly affecting the brain parenchyma and cisternal spaces. 20 (8.4%; mean age, 40.2 years) with large cystic lesions subsequently underwent surgical intervention, cither because of an emergent presentation or because they were refractory to medical management. Clinical presentation included increased intracranial pressure, focal neurological deficit, and seizure. Radiographic imaging (computed tomography and/or magnetic resonance imaging) demonstrated 12 cases with cisternal lesions, 7 with parenchymal lesions, and 1 involving both compartments. Based on imaging guidelines, 30 operative procedures (excluding shunt revisions) were performed (14 craniotomies, 8 cerebrospinal fluid diversions, 7 stereotactic procedures, and 1 burr hole drainage). Fifteen (75%) showed neurological or symptomatic improvement over a median follow-up period of 36.4 months. There were three surgery-related complications and no deaths
Neutrino Masses and A TeV Scale Seesaw Mechanism
A simple extension of the Standard Model providing TeV scale seesaw mechanism
is presented. Beside the Standard Model particles and right-handed Majorana
neutrinos, the model contains a singly charged scalar, an extra Higgs doublet
and three vector like singly charged fermions. In our model, Dirac neutrino
mass matrix raises only at the loop level. Small but non-zero Majorana neutrino
masses come from integrating out heavy Majorana neutrinos, which can be at the
TeV scale. The phenomenologies of the model are investigated, including scalar
mass spectrum, neutrino masses and mixings, lepton flavor violations, heavy
neutrino magnetic moments as well as possible collider signatures of the model
at the LHC.Comment: 13 pages, 4 figures. references adde
Universal Spectral Correlation between Hamiltonians with Disorder
We study the correlation between the energy spectra of two disordered
Hamiltonians of the form () with and
drawn from random distributions. We calculate this correlation
function explicitly and show that it has a simple universal form for a broad
class of random distributions.Comment: 9 pages, Jnl.tex Version 0.3 (version taken from the bulletin board),
NSF-ITP-93-13
Chern-Simons anomaly as polarization effect
The parity violating Chern-Simons term in the epoch before the electroweak
phase transition can be interpreted as a polarization effect associated to
massless right-handed electrons (positrons) in the presence of a large-scale
seed hypermagnetic field. We reconfirm the viability of a unified seed field
scenario relating the cosmological baryon asymmetry and the origin of the
protogalactic large-scale magnetic fields observed in astronomy.Comment: 4 pages, latex, matches published versio
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