5,279 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
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 Hellmann–Feynman Theorem: H2+ Molecule
It is by now well known that the integral Hellmann–Feynman (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
The Annual Cycle of SST in the Eastern Tropical Pacific, Diagnosed in an Ocean GCM
The annual onset of the east Pacific cold tongue is diagnosed in an ocean GCM simulation of the tropical Pacific. The model uses a mixed-layer scheme that explicitly simulates the processes of vertical exchange of heat and momentum with the deeper layers of the ocean; comparison with observations of temperature and currents shows that many important aspects of the model fields are realistic. As previous studies have found, the heat balance in the eastern tropical Pacific is notoriously complicated, and virtually every term in the balance plays a significant role at one time or another. However, despite many complications, the three-dimensional ocean advection terms in the cold tongue region tend to cancel each other in the annual cycle and, to first order, the variation of SST can be described as simply following the variation of net solar radiation at the sea surface (sun minus clouds). The cancellation is primarily between cooling due to equatorial upwelling and warming due to tropical instability waves, both of which are strongest in the second half of the year (when the winds are stronger). Even near the equator, where the ocean advection is relatively intense, the terms associated with cloudiness variations are among the largest contributions to the SST balance. The annual cycle of cloudiness transforms the semiannual solar cycle at the top of the atmosphere into a largely 1 cycle yr−1 variation of insolation at the sea surface. However, the annual cycle of cloudiness appears closely tied to SST in coupled feedbacks (positive for low stratus decks and negative for deep cumulus convection), so the annual cycle of SST cannot be fully diagnosed in an ocean-only modeling context as in the present study. Zonal advection was found to be a relatively small influence on annual equatorial cold tongue variations; in particular, there was little direct (oceanic) connection between the Peru coastal upwelling and equatorial annual cycles. Meridional advection driven by cross-equatorial winds has been conjectured as a key factor leading to the onset of the cold tongue. The results suggest that the SST changes due to this mechanism are modest, and if meridional advection is in fact a major influence, then it must be through interaction with another process (such as a coupled feedback with stratus cloudiness). At present, it is not possible to evaluate this feedback quantitatively
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