16,963 research outputs found
Conversion of neutron stars to strange stars as the central engine of gamma-ray bursts
We study the conversion of a neutron star to a strange star as a possible
energy source for gamma-ray bursts. We use different recent models for the
equation of state of neutron star matter and strange quark matter. We show that
the total amount of energy liberated in the conversion is in the range of (1-4)
10^{53} ergs (one order of magnitude larger than previous estimates) and is in
agreement with the energy required to power gamma-ray burst sources at
cosmological distances.Comment: ApJ, 530, 2000 February 20, Lxxx (in press
Super Rogers-Szeg\"o polynomials associated with type of Polychronakos spin chains
As is well known, multivariate Rogers-Szeg\"o polynomials are closely
connected with the partition functions of the type of Polychronakos
spin chains having long-range interactions. Applying the `freezing trick', here
we derive the partition functions for a class of type of Polychronakos
spin chains containing supersymmetric analogues of polarized spin reversal
operators and subsequently use those partition functions to obtain novel
multivariate super Rogers-Szeg\"o (SRS) polynomials depending on four types of
variables. We construct the generating functions for such SRS polynomials and
show that these polynomials can be written as some bilinear combinations of the
type of SRS polynomials. We also use the above mentioned generating
functions to derive a set of recursion relations for the partition functions of
the type of Polychronakos spin chains involving different numbers of
lattice sites and internal degrees of freedom.Comment: 33 pages, minor typos corrected, journal reference give
On a Generalized Fifth-Order Integrable Evolution Equation and its Hierarchy
A general form of the fifth-order nonlinear evolution equation is considered.
Helmholtz solution of the inverse variational problem is used to derive
conditions under which this equation admits an analytic representation. A
Lennard type recursion operator is then employed to construct a hierarchy of
Lagrangian equations. It is explicitly demonstrated that the constructed system
of equations has a Lax representation and two compatible Hamiltonian
structures. The homogeneous balance method is used to derive analytic soliton
solutions of the third- and fifth-order equations.Comment: 16 pages, 1 figur
Impact of built-in fields and contact configuration on the characteristics of ultra-thin GaAs solar cells
We discuss the effects of built-in fields and contact configuration on the
photovoltaic characteristics of ultrathin GaAs solar cells. The investigation
is based on advanced quantum-kinetic simulations reaching beyond the standard
semi-classical bulk picture concerning the consideration of charge carrier
states and dynamics in complex potential profiles. The thickness dependence of
dark and photocurrent in the ultra-scaled regime is related to the
corresponding variation of both, the built-in electric fields and associated
modification of the density of states, and the optical intensity in the films.
Losses in open-circuit voltage and short-circuit current due to leakage of
electronically and optically injected carriers at minority carrier contacts are
investigated for different contact configurations including electron and hole
blocking barrier layers. The microscopic picture of leakage currents is
connected to the effect of finite surface recombination velocities in the
semi-classical description, and the impact of these non-classical contact
regions on carrier generation and extraction is analyzed.Comment: 5 pages, 8 figure
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