6,245 research outputs found
Bounding the Tau Neutrino Magnetic Moment from Single Photon Searches at LEP
We show that single photon searches at LEP constrain the tau neutrino
magnetic moment to be less than . This bound is
competitive with low energy () single photon searches.Comment: 5 pgs. LaTeX, one reference fixed in revised version,
JHU-TIPAC-940004, UM-TH-94-1
Serre Duality, Abel's Theorem, and Jacobi Inversion for Supercurves Over a Thick Superpoint
The principal aim of this paper is to extend Abel's theorem to the setting of
complex supermanifolds of dimension 1|q over a finite-dimensional local
supercommutative C-algebra. The theorem is proved by establishing a
compatibility of Serre duality for the supercurve with Poincare duality on the
reduced curve. We include an elementary algebraic proof of the requisite form
of Serre duality, closely based on the account of the reduced case given by
Serre in Algebraic Groups and Class Fields, combined with an invariance result
for the topology on the dual of the space of repartitions. Our Abel map, taking
Cartier divisors of degree zero to the dual of the space of sections of the
Berezinian sheaf, modulo periods, is defined via Penkov's characterization of
the Berezinian sheaf as the cohomology of the de Rham complex of the sheaf D of
differential operators, as a right module over itself. We discuss the Jacobi
inversion problem for the Abel map and give an example demonstrating that if n
is an integer sufficiently large that the generic divisor of degree n is
linearly equivalent to an effective divisor, this need not be the case for all
divisors of degree n.Comment: 14 page
Effective field theory approach to Casimir interactions on soft matter surfaces
We utilize an effective field theory approach to calculate Casimir
interactions between objects bound to thermally fluctuating fluid surfaces or
interfaces. This approach circumvents the complicated constraints imposed by
such objects on the functional integration measure by reverting to a point
particle representation. To capture the finite size effects, we perturb the
Hamiltonian by DH that encapsulates the particles' response to external fields.
DH is systematically expanded in a series of terms, each of which scales
homogeneously in the two power counting parameters: \lambda \equiv R/r, the
ratio of the typical object size (R) to the typical distance between them (r),
and delta=kB T/k, where k is the modulus characterizing the surface energy. The
coefficients of the terms in DH correspond to generalized polarizabilities and
thus the formalism applies to rigid as well as deformable objects.
Singularities induced by the point particle description can be dealt with using
standard renormalization techniques. We first illustrate and verify our
approach by re-deriving known pair forces between circular objects bound to
films or membranes. To demonstrate its efficiency and versatility, we then
derive a number of new results: The triplet interactions present in these
systems, a higher order correction to the film interaction, and general scaling
laws for the leading order interaction valid for objects of arbitrary shape and
internal flexibility.Comment: 4 pages, 1 figur
Simulations of the Disk-Jet Interaction in GRS 1915+105 and Other Systems
After an X-ray binary experiences a transient jet ejection, it undergoes a
phase in which its X-ray light curve is dominated, for some time, by thermal
emission from an accretion disk surrounding the black hole. The accretion
physics in the thermal-dominant state is understood better than in any other,
and it is therefore the best state for comparing observations to theoretical
models. Here, I present simulations that study the way a thermally-emitting
disk might be expected to behave immediately after a large-scale, steady jet
has been removed from the system in the form of a sudden ejection. I simulate
the ejection's effect on the disk by allowing the strength of turbulence
(modeled by the alpha parameter of Shakura and Sunyaev) to increase rapidly in
time, and I show how this change can lead to an outburst in an otherwise-steady
disk. The motivation for treating the jet removal in this way is the fact that
many models for jets involve large-scale magnetic fields that should inhibit
the magnetorotational instability believed to drive turbulence; this should
naturally lead to a rapid increase in turbulence when the magnetic field is
ejected from the system or otherwise destroyed during the ejection event. I
show how the timescale and luminosity of the outburst can be controlled by the
manner in which alpha is allowed to change, and I briefly discuss ways in which
these simulations can be compared to observations of X-ray binaries, in
particular GRS 1915+105, which shows the most complex and variable behavior of
any black hole system in outburst.Comment: 10 pages, 6 figures; accepted for publication in the proceedings of
VI Microquasar Workshop: Microquasars and Beyond, Sept 18-22 2006, Como,
Italy, ed: T. Belloni (2006), PoS(MQW6)03
A Precision Model Independent Determination of |Vub| from B -> pi e nu
A precision method for determining |Vub| using the full range in q^2 of B->
pi \ell nu data is presented. At large q^2 the form factor is taken from
unquenched lattice QCD, at q^2=0 we impose a model independent constraint
obtained from B-> pi pi using the soft-collinear effective theory, and the
shape is constrained using QCD dispersion relations. We find |Vub| =(3.54\pm
0.17\pm 0.44) x 10^{-3}. With 5% experimental error and 12% theory error, this
is competitive with inclusive methods. Theory error is dominated by the input
points, with negligible uncertainty from the dispersion relations.Comment: 4 pages, 3 figure
Stability of Neutrinos in the Singlet Majoron Model
We show that there is no one-loop enhancement of the rate for a light
neutrino to decay into a lighter neutrino plus a majoron, contrary to a recent
claim. Thus the light neutrinos must satisfy the cosmological bound of having
masses less than 35 eV in the singlet majoron model, or else violate the
constraint imposed by galaxy formation. In the latter case, could
have a mass between 40 and 500 keV, while satisfying all other cosmological
constraints.Comment: 11 pp., latex, UMN-TH-1218-93. Correct nucleosynthesis bound of 500
keV on nu_tau mass is incorporated; one-loop electroweak contribution to
neutrino mass is correcte
Energy Expectation Values and the Integral HellmannâFeynman Theorem: H2+ Molecule
It is by now well known that the integral HellmannâFeynman (IHF) theorem has little quantitative utility for chemically interesting problems, although the formalism potentially affords a ready physical interpretation of changes in molecular conformation. In this paper, the IHF theorem is applied to variational and simple LCAO wavefunctions for the H2+ ground state, which range in quality from crude to essentially exact. The IHF results improve quite dramatically with the quality of the wavefunctions. This suggests that errors in the IHF formula may be of the same order as those in the wavefunction. (In contrast, errors in variationally determined energies are of second order.) Our results suggest a convenient test which can be applied to any revised IHF formalism developed in the future.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70096/2/JCPSA6-49-3-1284-1.pd
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