245 research outputs found
Towards an embedding of Graph Transformation in Intuitionistic Linear Logic
Linear logics have been shown to be able to embed both rewriting-based
approaches and process calculi in a single, declarative framework. In this
paper we are exploring the embedding of double-pushout graph transformations
into quantified linear logic, leading to a Curry-Howard style isomorphism
between graphs and transformations on one hand, formulas and proof terms on the
other. With linear implication representing rules and reachability of graphs,
and the tensor modelling parallel composition of graphs and transformations, we
obtain a language able to encode graph transformation systems and their
computations as well as reason about their properties
Theory-Motivated Benchmark Models and Superpartners at the Tevatron
Recently published benchmark models have contained rather heavy
superpartners. To test the robustness of this result, several benchmark models
have been constructed based on theoretically well-motivated approaches,
particularly string-based ones. These include variations on anomaly and
gauge-mediated models, as well as gravity mediation. The resulting spectra
often have light gauginos that are produced in significant quantities at the
Tevatron collider, or will be at a 500 GeV linear collider. The signatures also
provide interesting challenges for the LHC. In addition, these models usually
account for electroweak symmetry breaking with relatively less fine-tuning than
previous benchmark models.Comment: 44 pages, 4 figures; some typos corrected. Revisions reflect
published versio
One-Loop Pauli-Villars Regularization of Supergravity I: Canonical Gauge Kinetic Energy
It is shown that the one-loop coefficients of on-shell operators of standard
supergravity with canonical gauge kinetic energy can be regulated by the
introduction of Pauli-Villars chiral and abelian gauge multiplets, subject to a
condition on the matter representations of the gauge group. Aspects of the
anomaly structure of these theories under global nonlinear symmetries and an
anomalous gauge symmetry are discussed.Comment: 46 pages, full postscript also available from
http://phyweb.lbl.gov/theorygroup/papers/preprints.html/41981.ps . Misprints
and errors in equations present in the original version have been correcte
Exclusion limits on the WIMP-nucleon cross-section from the Cryogenic Dark Matter Search
The Cryogenic Dark Matter Search (CDMS) employs low-temperature Ge and Si
detectors to search for Weakly Interacting Massive Particles (WIMPs) via their
elastic-scattering interactions with nuclei while discriminating against
interactions of background particles. For recoil energies above 10 keV, events
due to background photons are rejected with >99.9% efficiency, and surface
events are rejected with >95% efficiency. The estimate of the background due to
neutrons is based primarily on the observation of multiple-scatter events that
should all be neutrons. Data selection is determined primarily by examining
calibration data and vetoed events. Resulting efficiencies should be accurate
to about 10%. Results of CDMS data from 1998 and 1999 with a relaxed
fiducial-volume cut (resulting in 15.8 kg-days exposure on Ge) are consistent
with an earlier analysis with a more restrictive fiducial-volume cut.
Twenty-three WIMP candidate events are observed, but these events are
consistent with a background from neutrons in all ways tested. Resulting limits
on the spin-independent WIMP-nucleon elastic-scattering cross-section exclude
unexplored parameter space for WIMPs with masses between 10-70 GeV c^{-2}.
These limits border, but do not exclude, parameter space allowed by
supersymmetry models and accelerator constraints. Results are compatible with
some regions reported as allowed at 3-sigma by the annual-modulation
measurement of the DAMA collaboration. However, under the assumptions of
standard WIMP interactions and a standard halo, the results are incompatible
with the DAMA most likely value at >99.9% CL, and are incompatible with the
model-independent annual-modulation signal of DAMA at 99.99% CL in the
asymptotic limit.Comment: 40 pages, 49 figures (4 in color), submitted to Phys. Rev. D;
v.2:clarified conclusions, added content and references based on referee's
and readers' comments; v.3: clarified introductory sections, added figure
based on referee's comment
One-loop Regularization of Supergravity II: The Dilaton and the Superfield Formulation
The on-shell regularization of the one-loop divergences of supergravity
theories is generalized to include a dilaton of the type occurring in effective
field theories derived from superstring theory, and the superfield structure of
the one-loop corrections is given. Field theory anomalies and quantum
contributions to soft supersymmetry breaking are discussed. The latter are
sensitive to the precise choice of couplings that generate Pauli-Villars
masses, which in turn reflect the details of the underlying theory above the
scale of the effective cut-off. With a view to the implementation the
Green-Schwarz and other mechanisms for canceling field theory anomalies under a
U(1) gauge transformation and under the T-duality group of modular
transformations, we show that the K\"ahler potential renormalization for the
untwisted sector of orbifold compactification can be made invariant under these
groups.Comment: 46 pages, full postscript also available from
http://phyweb.lbl.gov/theorygroup/papers/43259.p
Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events
The - oscillation frequency has been measured with a sample of
23 million \B\bar B pairs collected with the BABAR detector at the PEP-II
asymmetric B Factory at SLAC. In this sample, we select events in which both B
mesons decay semileptonically and use the charge of the leptons to identify the
flavor of each B meson. A simultaneous fit to the decay time difference
distributions for opposite- and same-sign dilepton events gives ps.Comment: 7 pages, 1 figure, submitted to Physical Review Letter
Desempenho de Lecanicillium lecanii em meios de cultura contendo vitaminas e concentraçÔes de extrato de levedura
Relativistic superfluid models for rotating neutron stars
This article starts by providing an introductory overview of the theoretical
mechanics of rotating neutron stars as developped to account for the frequency
variations, and particularly the discontinuous glitches, observed in pulsars.
The theory suggests, and the observations seem to confirm, that an essential
role is played by the interaction between the solid crust and inner layers
whose superfluid nature allows them to rotate independently. However many
significant details remain to be clarified, even in much studied cases such as
the Crab and Vela. The second part of this article is more technical,
concentrating on just one of the many physical aspects that needs further
development, namely the provision of a satisfactorily relativistic (local but
not microscopic) treatment of the effects of the neutron superfluidity that is
involved.Comment: 42 pages LateX. Contribution to Physics of Neutron Star Interiors,
ed. D. Blasche, N.K. Glendenning, A. Sedrakian (ECT workshop, Trento, June
2000
Distribution of Major Health Risks: Findings from the Global Burden of Disease Study
BACKGROUND: Most analyses of risks to health focus on the total burden of their aggregate effects. The distribution of risk-factor-attributable disease burden, for example by age or exposure level, can inform the selection and targeting of specific interventions and programs, and increase cost-effectiveness. METHODS AND FINDINGS: For 26 selected risk factors, expert working groups conducted comprehensive reviews of data on risk-factor exposure and hazard for 14 epidemiological subregions of the world, by age and sex. Age-sex-subregion-population attributable fractions were estimated and applied to the mortality and burden of disease estimates from the World Health Organization Global Burden of Disease database. Where possible, exposure levels were assessed as continuous measures, or as multiple categories. The proportion of risk-factor-attributable burden in different population subgroups, defined by age, sex, and exposure level, was estimated. For major cardiovascular risk factors (blood pressure, cholesterol, tobacco use, fruit and vegetable intake, body mass index, and physical inactivity) 43%â61% of attributable disease burden occurred between the ages of 15 and 59 y, and 87% of alcohol-attributable burden occurred in this age group. Most of the disease burden for continuous risks occurred in those with only moderately raised levels, not among those with levels above commonly used cut-points, such as those with hypertension or obesity. Of all disease burden attributable to being underweight during childhood, 55% occurred among children 1â3 standard deviations below the reference population median, and the remainder occurred among severely malnourished children, who were three or more standard deviations below median. CONCLUSIONS: Many major global risks are widely spread in a population, rather than restricted to a minority. Population-based strategies that seek to shift the whole distribution of risk factors often have the potential to produce substantial reductions in disease burden
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