1,450,277 research outputs found
Birational automorphisms of a three-dimensional double quadric with an elementary singularity
It is proved that the group of birational automorphisms of a
three-dimensional double quadric with a singular point arising from a double
point on the branch divisor is a semidirect product of the free group generated
by birational involutions of a special form and the group of regular
automorphisms. The proof is based on the method of `untwisting' maximal
singularities of linear systems.Comment: 18 page
Curie law, entropy excess, and superconductivity in heavy fermion metals and other strongly interacting Fermi liquids
Low-temperature thermodynamic properties of strongly interacting Fermi
liquids with fermion condensate are investigated. We demonstrate that the spin
susceptibility of these systems exhibits the Curie-Weiss law, and the entropy
contains a temperature-independent term. The excessive entropy is released at
the superconducting transition, enhancing the specific heat jump Delta C and
rendering it proportional to the effective Curie constant. The theoretical
results are favorably compared with the experimental data on the heavy fermion
metal CeCoIn5, as well as He-3 films.Comment: 4 pages, 2 figures. V.2: a reference added; minor changes as in the
published versio
Nucleon Form Factors from Generalized Parton Distributions
We discuss the links between Generalized Parton Distributions (GPDs) and
elastic nucleon form factors. These links, in the form of sum rules, represent
powerful constraints on parametrizations of GPDs. A Regge parametrization for
GPDs at small momentum transfer, is extended to the large momentum transfer
region and it is found to describe the basic features of proton and neutron
electromagnetic form factor data. This parametrization is used to estimate the
quark contribution to the nucleon spin.Comment: 18 pages, 5 figures, replaced with published versio
Probing confinement by direct photons and dileptons
The intensive synchrotron radiation resulting from quarks interacting with
the collective confining color field in relativistic heavy ion collisions is
discussed. The spectrum of photons with large transverse momentum is calculated
and compared with the experimental data to demonstrate the feasibility of this
type of radiation. A study of the earlier predicted azimuthal anisotropy in the
angular distribution of dileptons with respect to the three-momentum of the
pair is performed as well. This boundary-induced mechanism of lepton pair
production is shown to possess the features that are distinctly different from
the standard mechanisms and can potentially provide an efficient probe of
quark-gluon plasma formation.Comment: 7 pages, 3 figures, Fig., Refs. and explanations added, typos
corrected, text revise
Ultraslow Wave Nuclear Burning of Uranium-Plutonium Fissile Medium on Epithermal Neutrons
For a fissile medium, originally consisting of uranium-238, the investigation
of fulfillment of the wave burning criterion in a wide range of neutron
energies is conducted for the first time, and a possibility of wave nuclear
burning not only in the region of fast neutrons, but also for cold, epithermal
and resonance ones is discovered for the first time.
For the first time the results of the investigation of the Feoktistov
criterion fulfillment for a fissile medium, originally consisting of
uranium-238 dioxide with enrichments 4.38%, 2.00%, 1.00%, 0.71% and 0.50% with
respect to uranium-235, in the region of neutron energies 0.015-10.0eV are
presented. These results indicate a possibility of ultraslow wave
neutron-nuclear burning mode realization in the uranium-plutonium media,
originally (before the wave initiation by external neutron source) having
enrichments with respect to uranium-235, corresponding to the subcritical
state, in the regions of cold, thermal, epithermal and resonance neutrons.
In order to validate the conclusions, based on the slow wave neutron-nuclear
burning criterion fulfillment depending on the neutron energy, the numerical
modeling of ultraslow wave neutron-nuclear burning of a natural uranium in the
epithermal region of neutron energies (0.1-7.0eV) was conducted for the first
time. The presented simulated results indicate the realization of the ultraslow
wave neutron-nuclear burning of the natural uranium for the epithermal
neutrons.Comment: 35 pages, 19 figures (v2: Fig12 and some misprints in the text are
fixed
Boltzmann equations for mixtures of Maxwell gases: exact solutions and power like tails
We consider the Boltzmann equations for mixtures ofMaxwell gases. It is shown
that in certain limiting case the equations admit self-similar solutions that
can be constructed in explicit form. More precisely, the solutions have simple
explicit integral representations. The most interesting solutions have finite
energy and power like tails. This shows that power like tails can appear not
just for granular particles (Maxwell models are far from reality in this case),
but also in the system of particles interacting in accordance with laws of
classical mechanics. In addition, non-existence of positive self-similar
solutions with finite moments of any order is proven for a wide class of
Maxwell models.Comment: 20 page
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