36 research outputs found
Gravito-electromagnetism versus electromagnetism
The paper contains a discussion of the properties of the gravito-magnetic
interaction in non stationary conditions. A direct deduction of the equivalent
of Faraday-Henry law is given. A comparison is made between the
gravito-magnetic and the electro-magnetic induction, and it is shown that there
is no Meissner-like effect for superfluids in the field of massive spinning
bodies. The impossibility of stationary motions in directions not along the
lines of the gravito-magnetic field is found. Finally the results are discussed
in relation with the behavior of superconductors.Comment: 13 Pages, LaTeX, 1 EPS figure, to appear in European Journal of
Physic
Search for flavor-changing neutral currents and lepton-family-number violation in two-body D0 decays
Results of a search for the three neutral charm decays, D0 -> mu e, D0 -> mu
mu, and D0 -> e e, are presented. This study was based on data collected in
Experiment 789 at the Fermi National Accelerator Laboratory using 800 GeV/c
proton-Au and proton-Be interactions. No evidence is found for any of the
decays. Upper limits on the branching ratios, at the 90% confidence level, are
obtained.Comment: 28 pages, 18 figures. Submitted to Physical Review
Searching for dark matter with plasma haloscopes
We summarize the recent progress of the Axion Longitudinal Plasma Haloscope (ALPHA) Consortium, a new experimental collaboration to build a plasma haloscope to search for axions and dark photons. The plasma haloscope is a novel method for the detection of the resonant conversion of light dark matter to photons. ALPHA will be sensitive to QCD axions over almost a decade of parameter space, potentially discovering dark matter and resolving the strong CP problem. Unlike traditional cavity haloscopes, which are generally limited in volume by the Compton wavelength of the dark matter, plasma haloscopes use a wire metamaterial to create a tuneable artificial plasma frequency, decoupling the wavelength of light from the Compton wavelength and allowing for much stronger signals. We develop the theoretical foundations of plasma haloscopes and discuss recent experimental progress. Finally, we outline a baseline design for ALPHA and show that a full-scale experiment could discover QCD axions over almost a decade of parameter space
Equilibrium configurations of two charged masses in General Relativity
An asymptotically flat static solution of Einstein-Maxwell equations which
describes the field of two non-extreme Reissner - Nordstr\"om sources in
equilibrium is presented. It is expressed in terms of physical parameters of
the sources (their masses, charges and separating distance). Very simple
analytical forms were found for the solution as well as for the equilibrium
condition which guarantees the absence of any struts on the symmetry axis. This
condition shows that the equilibrium is not possible for two black holes or for
two naked singularities. However, in the case when one of the sources is a
black hole and another one is a naked singularity, the equilibrium is possible
at some distance separating the sources. It is interesting that for
appropriately chosen parameters even a Schwarzschild black hole together with a
naked singularity can be "suspended" freely in the superposition of their
fields.Comment: 4 pages; accepted for publication in Phys. Rev.
Measurement of Differences Between J/Psi and Psi' Suppression in p-A Collisions
Measurements of the suppression of the yield per nucleon of J/Psi and Psi'
production for 800 GeV/c protons incident on heavy relative to light nuclear
targets have been made with very broad coverage in xF and pT. The observed
suppression is smallest at xF values of 0.25 and below and increases at larger
values of xF. It is also strongest at small pT. Substantial differences between
the Psi' and J/Psi are observed for the first time in p-A collisions. The
suppression for the Psi' is stronger than that for the J/Psi for xF near zero,
but becomes comparable to that for the J/Psi for xF > 0.6.Comment: 5 pages, 4 figures, accepted for publication by PR
Sub-Kelvin cooling for two kilopixel bolometer arrays in the PIPER receiver
The Primordial Inflation Polarization Explorer (PIPER) is a balloon-borne telescope mission to search for inflationary gravitational waves from the early universe. PIPER employs two 32 Ă 40 arrays of superconducting transition-edge sensors, which operate at 100 mK. An open bucket Dewar of liquid helium maintains the receiver and telescope optics at 1.7 K. We describe the thermal design of the receiver and sub-Kelvin cooling with a continuous adiabatic demagnetization refrigerator (CADR). The CADR operates between 70 and 130 mK and provides â10 ÎŒW cooling power at 100 mK, nearly five times the loading of the two detector assemblies. We describe electronics and software to robustly control the CADR, overall CADR performance in flightlike integrated receiver testing, and practical considerations for implementation in the balloon float environment
Literature on postsecondary disability services: A call for research guidelines.
Support services for students with disabilities is now a distinct field of practice in higher education, with a significant increase in the number of students receiving services, programs to serve them, and professionals who oversee the programs. The field has professional and program standards, a code of ethics, and a disability service specific professional organization. Correspondingly, an extensive corpus of professional literature has emerged. However, though the research base has great breadth, it lacks significant depth, has poor sample and setting descriptions, and lacks methodological rigor. The result is that there is insufficient evidence spelling out what practices work with which students and in which settings. Guidelines intended to steer future research could have significant impact upon scholars conducting research and, subsequently, higher education. The present article describes the current state of the research base and proposes future directions to guide research