2,299 research outputs found
VIA RASELLA, 1944: MEMORY, TRUTH, AND HISTORY
The facts: what happened? On 23 March 1944, a column of 156 police troops from the Bolzen regiment attached to the German army were marching through the centre of occupied Rome. Between 15.45 and 15.50 a bomb exploded in the narrow street of Via Rasella killing thirty military policemen (three more were to die later) as well as at least two Italian civilians. The bomb had been placed by an official armed Gap partisan unit which had been active in Rome for some months. The German troops responded by firing indiscriminately into the houses on the street and rounding up the residents of Via Rasella. The next day, 335 people were taken to the Fosse Ardeatine Caves just outside the city and shot over a period of four and a half hours. 1 The victims had been taken from various official and unofficial prisons, Via Rasella, and other areas. Only three had already been condemned to death (for partisan activity), 154 were under investigation by the Germany military police, and seventy-five were in custody purely because they were Jewish. Other victims were taken from Regina Coeli (Rome's prison) or selected from those picked up around Via Rasella. The next day (25 March) a German army poster appeared across Rome and in newspapers. It accused ‘criminal elements’ of planting the bomb and added that ‘The German Command … has ordered that for every German killed ten communist-Badoglian criminals will be shot. This order has already been carried out.
Near infrared radiances observed by the UK C130 multi-channel radiometer during the marine stratocumulus IFO and preliminary comparison with model calculations
A preliminary analysis of some of the narrow band radiance data measured on the U.K. Meteorological Office's C130 aircraft during the marine stratocumulus intensive field observation of First ISCCP Regional Experiment (FIRE), San Diego 29 June to 18 July 1987, is presented. The data are compared with Monte Carlo calculations of the reflectance and transmittance of the cloud based upon the observed droplet size distribution. The main scientific question being addressed is whether there is any evidence of anomalous absorption within the cloud which had been observed in similar measurements (Rozenberg et al., 1974; Twomey and Cocks, 1982; Foot, 1988). The measurements also indicate the potential for remotely sensing cloud properties. The data and method of presentation discussed here clearly separates out clouds in terms of the size of the cloud droplets. All of the daytime C130 FIRE flights have been studied and are consistent with the data presented here. There appears to be no peculiarities that might arise, for example if pollution were to be a significant factor in determining cloud absorption. Variation in the inferred size parameters, r sub e, along runs are also very small
Electric Charge Quantization
Experimentally it has been known for a long time that the electric charges of
the observed particles appear to be quantized. An approach to understanding
electric charge quantization that can be used for gauge theories with explicit
factors -- such as the standard model and its variants -- is
pedagogically reviewed and discussed in this article. This approach uses the
allowed invariances of the Lagrangian and their associated anomaly cancellation
equations. We demonstrate that charge may be de-quantized in the
three-generation standard model with massless neutrinos, because differences in
family-lepton--numbers are anomaly-free. We also review the relevant
experimental limits. Our approach to charge quantization suggests that the
minimal standard model should be extended so that family-lepton--number
differences are explicitly broken. We briefly discuss some candidate extensions
(e.g. the minimal standard model augmented by Majorana right-handed neutrinos).Comment: 18 pages, LaTeX, UM-P-92/5
Mirror dark matter will be confirmed or excluded by XENON1T
Mirror dark matter, where dark matter resides in a hidden sector exactly
isomorphic to the standard model, can be probed via direct detection
experiments by both nuclear and electron recoils if the kinetic mixing
interaction exists. In fact, the kinetic mixing interaction appears to be a
prerequisite for consistent small scale structure: Mirror dark matter halos
around spiral galaxies are dissipative - losing energy via dark photon
emission. This ongoing energy loss requires a substantial energy input, which
can be sourced from ordinary supernovae via kinetic mixing induced processes in
the supernova's core. Astrophysical considerations thereby give a lower limit
on the kinetic mixing strength, and indeed lower limits on both nuclear and
electron recoil rates in direct detection experiments can be estimated. We show
here that potentially all of the viable parameter space will be probed in
forthcoming XENON experiments including LUX and XENON1T. Thus, we anticipate
that these experiments will provide a definitive test of the mirror dark matter
hypothesis.Comment: about 10 page
Bose gas: Theory and Experiment
For many years, He typified Bose-Einstein superfluids, but recent
advances in dilute ultra-cold alkali-metal gases have provided new neutral
superfluids that are particularly tractable because the system is dilute. This
chapter starts with a brief review of the physics of superfluid He,
followed by the basic ideas of Bose-Einstein condensation (BEC), first for an
ideal Bose gas and then considering the effect of interparticle interactions,
including time-dependent phenomena. Extensions to more exotic condensates
include magnetic dipolar gases, mixtures of two components, and spinor
condensates that require a focused infrared laser for trapping of all the
various hyperfine magnetic states in a particular hyperfine manifold of
states. With an applied rotation, the trapped BECs nucleate quantized
vortices. Recent theory and experiment have shown that laser coupling fields
can mimic the effect of rotation. The resulting synthetic gauge fields have
produced vortices in a nonrotating condensate
Properties of quasi two-dimensional condensates in highly anisotropic traps
We theoretically investigate some of the observable properties of quasi
two-dimensional condensates. Using a variational model based on a
Gaussian-parabolic trial wavefunction we calculate chemical potential,
condensate size in time-of-flight, release energy and collective excitation
spectrum for varying trap geometries and atom numbers and find good agreement
with recent published experimental results.Comment: 7 pages, 4 figure
Electric charge quantization without anomalies?
In gauge theories like the standard model, the electric charges of the
fermions can be heavily constrained from the classical structure of the theory
and from the cancellation of anomalies. We argue that the anomaly conditions
are not quite as well motivated as the classical constraints, since it is
possible that new fermions could exist which cancel potential anomalies. For
this reason we examine the classically allowed electric charges of the known
fermions and we point out that the electric charge of the tau neutrino is
classically allowed to be non-zero. The experimental bound on the electric
charge of the tau neutrino is many orders of magnitude weaker than for any
other known neutrino. We discuss possible modifications of the minimal standard
model such that electric charge is quantized classically.Comment: 10 McGill/93-3
Solutions of the atmospheric, solar and LSND neutrino anomalies from TeV scale quark-lepton unification
There is a unique gauge model which
allows quarks and leptons to be unified at the TeV scale. It is already known
that the neutrino masses arise radiatively in the model and are naturally
light. We study the atmospheric, solar and LSND neutrino anomalies within the
framework of this model.Comment: Minor changes, 31 page
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