2,879 research outputs found
Emergent Electroweak Gravity
We show that any massive cosmological relic particle with small
self-interactions is a super-fluid today, due to the broadening of its wave
packet, and lack of any elastic scattering. The WIMP dark matter picture is
only consistent its mass in order to maintain classicality.
The dynamics of a super-fluid are given by the excitation spectrum of bound
state quasi-particles, rather than the center of mass motion of constituent
particles. If this relic is a fermion with a repulsive interaction mediated by
a heavy boson, such as neutrinos interacting via the , the condensate has
the same quantum numbers as the vierbein of General Relativity. Because there
exists an enhanced global symmetry among
the fermion's self-interactions broken only by its kinetic term, the long
wavelength fluctuation around this condensate is a Goldstone graviton. A
gravitational theory exists in the low energy limit of the Standard Model's
Electroweak sector below the weak scale, with a strength that is parametrically
similar to .Comment: 4 page
Laboratory tests for the cosmic neutrino background using beta-decaying nuclei
We point out that the Pauli blocking of neutrinos by cosmological relic
neutrinos can be a significant effect. For zero-energy neutrinos, the standard
parameters for the neutrino background temperature and density give a
suppression of approximately 1/2. We show the effect this has on three-body
beta decays. The size of the effect is of the same order as the recently
suggested neutrino capture on beta-decaying nuclei.Comment: 4 pages, 2 figures, contribution to procedings of PANIC 200
Invisible Quarkonium Decays as a Sensitive Probe of Dark Matter
We examine in a model-independent manner the measurements that can be
performed at B-factories with sensitivity to dark matter. If a singlet scalar,
pseudo-scalar, or vector is present and mediates the Standard Model - dark
matter interaction, it can mediate invisible decays of quarkonium states such
as the , , and . Such scenarios have arisen in the
context of supersymmetry, extended Higgs sectors, solutions the supersymmetric
problem, and extra U(1) gauge groups from grand unified theories and
string theory. Existing B-factories running at the can produce
lower resonances by emitting an Initial State Radiation (ISR)
photon. Using a combination of ISR and radiative decays, the initial state of
an invisibly decaying quarkonium resonance can be tagged, giving sensitivity to
the spin and CP-nature of the particle that mediates standard model-dark matter
interactions. These measurements can discover or place strong constraints on
dark matter scenarios where the dark matter is approximately lighter than the
-quark. For the decay chains
(n=2,3) we analyze the dominant backgrounds and determine that with collected at the , the B-factories can limit
BR(\Upsilon(1S) \to invisible) \lsim 0.1%.Comment: 20 pages, 1 figure, accepted for publication in PR
VEGA Pathfinder navigation for Giotto Halley encounter
Results of the VEGA Pathfinder concept which was used to successfully target the European Space Agnecy's Giotto spacecraft to a 600 km encounter with the comet Halley are presented. Pathfinder was an international cooperative navigation activity involving USSR, European and U.S. space agencies. The final Giotto targeting maneuver was based on a comet location determined from optical data acquired by the earlier arriving Soviet VEGA spacecraft. Inertial pointing angles extracted from optical images of the comet nucleus were combined with a precise estimate of the VEGA encounter orbits determined using VLBI data acquired by NASA's Deep Space Network to predict the location of Halley at Giotto encounter. This article describes the VLBI techniques used to determine the VEGA orbits and shows that the insensitivity of the VLBI data strategy to unmodeled dynamic error sources resulted in estimates of the VEGA orbits with an accuracy of 50 km
On The Origin of Neutrino Mass and Mixing in the Standard Model
One can describe cosmological relic neutrinos by adding Lagrange multipliers to the Standard Model Lagrangian for them. The two possible Lagrange multipliers are a chemical potential, which fixes the mean neutrino/anti-neutrino asymmetry, and a Majorana mass, which fixes the mean spin-entropy. Because these neutrinos originated from a thermal bath, their entropy should be maximal, implying that each state in the background is a symmetric superposition of a neutrino and anti-neutrino. Therefore the Standard Model must be augmented by a flavor-diagonal Majorana neutrino mass matrix. This impacts the propagator via tadpole diagrams due to self-interactions. In the low-energy limit, neutrino self-interactions are entirely off-diagonal because same-flavor four-fermion operators vanish by Pauli exclusion. These interactions must be diagonalized when propagating through a bath of neutrinos, using the U(3) global flavor symmetry. U(3) gets broken broken down to SO(3) by Majorana masses, and down to if the three masses are different. Thus our universe today contains tri-bimaximal mixing and Majorana neutrinos. Neutrino mixing is due to the mismatch between the flavor-diagonal Majorana mass matrix arising at finite density and the self-interaction diagonal finite density propagator. The mass hierarchy is inverted and Majorana phases are absent. Lepton number is conserved and the neutrino-less double beta decay experiment absorbs a pair of neutrinos from the relic background and will prove their Majorana nature.One can describe cosmological relic neutrinos by adding Lagrange multipliers to the Standard Model Lagrangian for them. The two possible Lagrange multipliers are a chemical potential, which fixes the mean neutrino/anti-neutrino asymmetry, and a Majorana mass, which fixes the mean spin-entropy. Because these neutrinos originated from a thermal bath, their entropy should be maximal, implying that each state in the background is a symmetric superposition of a neutrino and anti-neutrino. Therefore the Standard Model must be augmented by a flavor-diagonal Majorana neutrino mass matrix. This impacts the propagator via tadpole diagrams due to self-interactions. In the low-energy limit, neutrino self-interactions are entirely off-diagonal because same-flavor four-fermion operators vanish by Pauli exclusion. These interactions must be diagonalized when propagating through a bath of neutrinos, using the U(3) global flavor symmetry. U(3) gets broken broken down to SO(3) by Majorana masses, and down to if the three masses are different. Thus our universe today contains tri-bimaximal mixing and Majorana neutrinos. Neutrino mixing is due to the mismatch between the flavor-diagonal Majorana mass matrix arising at finite density and the self-interaction diagonal finite density propagator. The mass hierarchy is inverted and Majorana phases are absent. Lepton number is conserved and the neutrino-less double beta decay experiment absorbs a pair of neutrinos from the relic background and will prove their Majorana nature
Fact, fiction, and function: mythmaking and the social construction of ecstasy use.
Myths and folklore about drugs represent important aspects of users subcultures. This paper explores Ecstasy users' perceptions about drug folklore as it relates to the social relationships of drug user lifestyles. The data for the study were collected through in-depth interviews with 50 current or former Ecstasy users in Northern Ireland. The findings indicate that although some Ecstasy users perceive the folklore to be an accurate reflection of reality others report that social relatiojns among users change with continued usage, occur within selected venues, or are influenced by greater cultural relations that characterise mainstream society
The school food environment and student body mass index and food consumption: 2004 to 2007 national data
PURPOSE: This study identifies trends in the availability of various food choices in United States' middle and high schools from 2004 to 2007, and examines the potential associations between such food availability and students' self-reported eating habits and body mass index (BMI)-related outcomes.
METHODS: Data are based on nationally representative samples of 78,442 students in 684 secondary schools surveyed from 2004 to 2007 as part of the Youth, Education, and Society (YES) study and the Monitoring the Future (MTF) study. In the YES study, school administrators and food service managers completed self-administered questionnaires on their school's food environment. In the MTF study, students in the same schools completed self-administered questionnaires, providing data used to construct BMI and food consumption measures.
RESULTS: Overall, there was a decrease in the availability of regular-sugar/fat food items in both middle and high schools, and some indication of an increase in high school availability of reduced-fat food items through school lunch or a la carte. Some minimal evidence was found for relationships between the school food environment and student BMI-related outcomes and food consumption measures.
CONCLUSIONS: United States secondary schools are making progress in the types of foods offered to students, with food items of lower nutritional value becoming less prevalent in recent years. Continued monitoring of food environment trends may help clarify whether and how such factors relate to youth health outcomes.The Youth, Education, and Society (YES) project (part of a larger research initiative, entitled Bridging the Gap: Research Informing Policy and Practice for Healthy Youth Behavior) is funded by the Robert Wood Johnson Foundation. The Monitoring the Future study is funded by the National Institute on Drug Abuse (DA01411). The views expressed in this article are those of the authors and do not necessarily reflect the views of the funders. (Robert Wood Johnson Foundation; DA01411 - National Institute on Drug Abuse
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