2,433 research outputs found
Vortex solutions in axial or chiral coupled non-relativistic spinor- Chern-Simons theory
The interaction of a spin 1/2 particle (described by the non-relativistic
"Dirac" equation of L\'evy-Leblond) with Chern-Simons gauge fields is studied.
It is shown, that similarly to the four dimensional spinor models, there is a
consistent possibility of coupling them also by axial or chiral type currents.
Static self dual vortex solutions together with a vortex-lattice are found with
the new couplings.Comment: Plain TEX, 10 page
Diffusion, Fragmentation and Coagulation Processes: Analytical and Numerical Results
We formulate dynamical rate equations for physical processes driven by a
combination of diffusive growth, size fragmentation and fragment coagulation.
Initially, we consider processes where coagulation is absent. In this case we
solve the rate equation exactly leading to size distributions of Bessel type
which fall off as for large -values. Moreover, we provide
explicit formulas for the expansion coefficients in terms of Airy functions.
Introducing the coagulation term, the full non-linear model is mapped exactly
onto a Riccati equation that enables us to derive various asymptotic solutions
for the distribution function. In particular, we find a standard exponential
decay, , for large , and observe a crossover from the Bessel
function for intermediate values of . These findings are checked by
numerical simulations and we find perfect agreement between the theoretical
predictions and numerical results.Comment: (28 pages, 6 figures, v2+v3 minor corrections
05/18/1993 - Eastern\u27s 1993 All Student Show Winner Laura Brahos.pdf
This paper reports on the stages forming a model evaluation protocol for urban flow and dispersion models proposed within the COST Action 732 on "Quality Assurance and Improvement of Micro-Scale Meteorological Models". It discusses the different components forming model evaluation with emphasis on validation and implementation of the protocol for the test case Mock Urban Setting Test (MUST). The protocol was proposed with building-resolving models in mind, but integral models have also been included. The suggested approach can be used for further micro-scale model evaluation and for the standardisation of their applications
Evolution of FLRW spacetime after the birth of a cosmic string
We consider the evolution of an initially FLRW universe after the formation
of a long, straight, cosmic string with arbitrary tension and mass per unit
length. The birth of the string sources scalar and tensor-type perturbations in
the background metric and both density and velocity perturbations in the
background fluid, which compensate for the string mass and maintain energy
conservation. The former generate the deficit angle within the light cone of
the string and a gravitational shock front at the cosmological horizon, whereas
the latter are confined within the sound cone. We study the properties of the
metric within each region of the resulting spacetime and give the explicit
coordinate transformations which demonstrate non-violation of causality. This
paper generalizes the work of previous studies for the Nambu-Goto string.Comment: 16 pages, 2 figures, published versio
Nucleation of quark matter bubbles in neutron stars
The thermal nucleation of quark matter bubbles inside neutron stars is
examined for various temperatures which the star may realistically encounter
during its lifetime. It is found that for a bag constant less than a critical
value, a very large part of the star will be converted into the quark phase
within a fraction of a second. Depending on the equation of state for neutron
star matter and strange quark matter, all or some of the outer parts of the
star may subsequently be converted by a slower burning or a detonation.Comment: 13 pages, REVTeX, Phys.Rev.D (in press), IFA 93-32. 5 figures (not
included) available upon request from [email protected]
A Gauge-invariant Analysis of Magnetic Fields in General Relativistic Cosmology
We provide a fully general-relativistic treatment of cosmological
perturbations in a universe permeated by a large-scale primordial magnetic
field, using the Ellis-Bruni gauge-invariant formalism. The exact non-linear
equations for general relativistic magnetohydrodynamic evolution are derived. A
number of applications are made: the behaviour of small perturbations to
Friedmann universes are studied; a comparison is made with earlier Newtonian
treatments of cosmological perturbations and some effects of inflationary
expansion are examined.Comment: 31 pages, Latex, Submitted to Classical and Quantum Gravit
Naupliar and Metanaupliar development of Thysanoessa raschii (Malacostraca, Euphausiacea) from GodthÄbsfjord, Greenland, with a reinstatement of the ancestral status of the free-living Nauplius in Malacostracan evolution
The presence of a characteristic crustacean larval type, the nauplius, in many crustacean taxa has often been considered one of the few uniting characters of the Crustacea. Within Malacostraca, the largest crustacean group, nauplii are only present in two taxa, Euphauciacea (krill) and Decapoda Dendrobranchiata. The presence of nauplii in these two taxa has traditionally been considered a retained primitive characteristic, but free-living nauplii have also been suggested to have reappeared a couple of times from direct developing ancestors during malacostracan evolution. Based on a re-study of Thysanoessa raschii (Euphausiacea) using preserved material collected in Greenland, we readdress this important controversy in crustacean evolution, and, in the process, redescribe the naupliar and metanaupliar development of T. raschii. In contrast to most previous studies of euphausiid development, we recognize three (not two) naupliar (= ortho-naupliar) stages (N1-N3) followed by a metanauplius (MN). While there are many morphological changes between nauplius 1 and 2 (e.g., appearance of long caudal setae), the changes between nauplius 2 and 3 are few but distinct. They involve the size of some caudal spines (largest in N3) and the setation of the antennal endopod (an extra seta in N3). A wider comparison between free-living nauplii of both Malacostraca and non-Malacostraca revealed similarities between nauplii in many taxa both at the general level (e.g., the gradual development and number of appendages) and at the more detailed level (e.g., unclear segmentation of naupliar appendages, caudal setation, presence of frontal filaments). We recognize these similarities as homologies and therefore suggest that free-living nauplii were part of the ancestral malacostracan type of development. The derived morphology (e.g., lack of feeding structures, no fully formed gut, high content of yolk) of both euphausiid and dendrobranchiate nauplii is evidently related to their non-feeding (lecithotrophic) status
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