13,584 research outputs found
A new possibility to monitor collisions of relativistic heavy ions at LHC and RHIC
We consider the radiation of particles of one bunch in the collective field
of the oncoming bunch, called coherent bremsstrahlung (CBS). The main
characteristics of CBS for LHC (in the Pb-Pb mode) and for RHIC are calculated.
At LHC about photons per second are expected for
photon energies eV. It seems that CBS
can be a potential tool for optimizing collisions and for measuring beam
parameters. The bunch length can be found from the critical energy of the CBS
spectrum; the transverse bunch size is related to the photon rate. A specific
dependence of photon rate on the impact parameter between the beams allows for
a fast control over the beam displacement.Comment: 9 pages + 4 figures, latex with poscript figures uuencode
Shape transformations in rotating ferrofluid drops
Floating drops of magnetic fluid can be brought into rotation by applying a
rotating magnetic field. We report theoretical and experimental results on the
transition from a spheroid equilibrium shape to non-axissymmetrical three-axes
ellipsoids at certain values of the external field strength. The transitions
are continuous for small values of the magnetic susceptibility and show
hysteresis for larger ones. In the non-axissymmetric shape the rotational
motion of the drop consists of a vortical flow inside the drop combined with a
slow rotation of the shape. Nonlinear magnetization laws are crucial to obtain
quantitative agreement between theory and experiment.Comment: 4 pages, 3 figure
Ultra-High Energy Cosmic Rays: Some General Features, and Recent Developments Concerning Air Shower Computations
We present an introductory lecture on general features of cosmic rays, for
non-experts, and some recent developments concerning cascade equations for air
shower developments.Comment: invited talk, presented at the Hadron-RANP2004 worksho
The perturbative odderon in elastic p p and p pbar scattering
Different models for the odderon-proton coupling are considered and their
effects on the differential cross section in the dip region in elastic p p and
p pbar scattering are investigated. An allowed range for the size of a possible
diquark cluster in the proton can be obtained from a geometrical model.Comment: Talk presented at the conference QCD 02 in Montpellier, France. 4
pages, 3 figure
Thermodynamics of the L\'evy spin glass
We investigate the L\'evy glass, a mean-field spin glass model with power-law
distributed couplings characterized by a divergent second moment. By combining
extensively many small couplings with a spare random backbone of strong bonds
the model is intermediate between the Sherrington-Kirkpatrick and the
Viana-Bray model. A truncated version where couplings smaller than some
threshold \eps are neglected can be studied within the cavity method
developed for spin glasses on locally tree-like random graphs. By performing
the limit \eps\to 0 in a well-defined way we calculate the thermodynamic
functions within replica symmetry and determine the de Almeida-Thouless line in
the presence of an external magnetic field. Contrary to previous findings we
show that there is no replica-symmetric spin glass phase. Moreover we determine
the leading corrections to the ground-state energy within one-step replica
symmetry breaking. The effects due to the breaking of replica symmetry appear
to be small in accordance with the intuitive picture that a few strong bonds
per spin reduce the degree of frustration in the system
The effect of a cutoff on pushed and bistable fronts of the reaction diffusion equation
We give an explicit formula for the change of speed of pushed and bistable
fronts of the reaction diffusion equation when a small cutoff is applied at the
unstable or metastable equilibrium point. The results are valid for arbitrary
reaction terms and include the case of density dependent diffusion.Comment: 7 page
Binary jumps in continuum. II. Non-equilibrium process and a Vlasov-type scaling limit
Let denote the space of all locally finite subsets (configurations)
in . A stochastic dynamics of binary jumps in continuum is a
Markov process on in which pairs of particles simultaneously hop over
. We discuss a non-equilibrium dynamics of binary jumps. We prove
the existence of an evolution of correlation functions on a finite time
interval. We also show that a Vlasov-type mesoscopic scaling for such a
dynamics leads to a generalized Boltzmann non-linear equation for the particle
density
On the Neutralino as Dark Matter Candidate - II. Direct Detection
Evaluations of the event rates relevant to direct search for dark matter
neutralino are presented for a wide range of neutralino masses and for various
detector materials of preeminent interest. Differential and total rates are
appropriately weighted over the local neutralino density expected on
theoretical grounds.Comment: (18 pages plain TeX, 24 figures not included, available from the
authors) DFTT-38/9
Equilibrium spin currents: Non-Abelian gauge invariance and color diamagnetism in condensed matter
The spin-orbit (SO) interaction in condensed matter can be described in terms
of a non-Abelian potential known in high-energy physics as a color field. I
show that a magnetic component of this color field inevitably generates
diamagnetic color currents which are just the equilibrium spin currents
discussed in a condensed matter context. These dissipationless spin currents
thus represent a universal property of systems with SO interaction. In
semiconductors with linear SO coupling the spin currents are related to the
effective non-Abelian field via Yang-Mills magnetostatics equation.Comment: RevTeX, 4 page
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