1,317 research outputs found
IDE spatio-temporal impact fluxes and high time-resolution studies of multi-impact events and long-lived debris clouds
The purpose of the Interplanetary Dust Experiment (IDE) on the Long Duration Exposure Facility (LDEF) was to sample the cosmic dust environment and to use the spatio-temporal aspect of the experiment to distinguish between the various components of the environment: zodiacal cloud, beta meteoroids, meteor streams, interstellar dust, and orbital debris. It was found that the introduction of precise time and even rudimentary directionality as co-lateral observables in sampling the particulate environment in near-Earth space produces an enormous qualitative improvement in the information content of the impact data. The orbital debris population is extremely clumpy, being dominated by persistent clouds in which the fluxes may rise orders of magnitude above the background. The IDE data suggest a strategy to minimize the damage to sensitive spacecraft components, using the observed characteristics of cloud encounters
Interaction of Low - Energy Induced Gravity with Quantized Matter -- II. Temperature effects
At the very early Universe the matter fields are described by the GUT models
in curved space-time. At high energies these fields are asymptotically free and
conformally coupled to external metric. The only possible quantum effect is the
appearance of the conformal anomaly, which leads to the propagation of the new
degree of freedom - conformal factor. Simultaneously with the expansion of the
Universe, the scale of energies decreases and the propagating conformal factor
starts to interact with the Higgs field due to the violation of conformal
invariance in the matter fields sector. In a previous paper \cite{foo} we have
shown that this interaction can lead to special physical effects like the
renormalization group flow, which ends in some fixed point. Furthermore in the
vicinity of this fixed point there occur the first order phase transitions. In
the present paper we consider the same theory of conformal factor coupled to
Higgs field and incorporate the temperature effects. We reduce the complicated
higher-derivative operator to several ones of the standard second-derivative
form and calculate an exact effective potential with temperature on the anti de
Sitter (AdS) background.Comment: 12 pages, LaTex - 2 Figure
Long Duration Exposure Facility (LDEF) attitude measurements of the Interplanetary Dust Experiment
Analysis of the data from the Long Duration Exposure Facility (LDEF) Interplanetary Dust Experiment (IDE) sun sensors has allowed a confirmation of the attitude of LDEF during its first year in orbit. Eight observations of the yaw angle at specific times were made and are tabulated in this paper. These values range from 4.3 to 12.4 deg with maximum uncertainty of plus or minus 2.0 deg and an average of 7.9 deg. No specific measurements of pitch or roll were made but the data indicates that LDEF had an average pitch down attitude of less than 0.7 deg
Bicrossed products for finite groups
We investigate one question regarding bicrossed products of finite groups
which we believe has the potential of being approachable for other classes of
algebraic objects (algebras, Hopf algebras). The problem is to classify the
groups that can be written as bicrossed products between groups of fixed
isomorphism types. The groups obtained as bicrossed products of two finite
cyclic groups, one being of prime order, are described.Comment: Final version: to appear in Algebras and Representation Theor
Quantum spin coverings and statistics
SL_q(2) at odd roots of unity q^l =1 is studied as a quantum cover of the
complex rotation group SO(3,C), in terms of the associated Hopf algebras of
(quantum) polynomial functions. We work out the irreducible corepresentations,
the decomposition of their tensor products and a coquasitriangular structure,
with the associated braiding (or statistics). As an example, the case l=3 is
discussed in detail.Comment: 15 page
Quantum Algebras Associated With Bell States
The antisymmetric solution of the braided Yang--Baxter equation called the
Bell matrix becomes interesting in quantum information theory because it can
generate all Bell states from product states. In this paper, we study the
quantum algebra through the FRT construction of the Bell matrix. In its four
dimensional representations via the coproduct of its two dimensional
representations, we find algebraic structures including a composition series
and a direct sum of its two dimensional representations to characterize this
quantum algebra. We also present the quantum algebra using the FRT construction
of Yang--Baxterization of the Bell matrix.Comment: v1: 15 pages, 2 figures, latex; v2: 18 pages, 2 figures, latex,
references and notes adde
Wodzicki Residue for Operators on Manifolds with Cylindrical Ends
We define the Wodzicki Residue TR(A) for A in a space of operators with
double order (m_1,m_2). Such operators are globally defined initially on R^n
and then, more generally, on a class of non-compact manifolds, namely, the
manifolds with cylindrical ends. The definition is based on the analysis of the
associate zeta function. Using this approach, under suitable ellipticity
assumptions, we also compute a two terms leading part of the Weyl formula for a
positive selfadjoint operator belonging the mentioned class in the case
m_1=m_2.Comment: 24 pages, picture changed, added references, corrected typo
Equivalence of -bosons using the exponential phase operator
Various forms of the -boson are explained and their hidden symmetry
revealed by transformations using the exponential phase operator. Both the
one-component and the multicomponent -bosons are discussed. As a byproduct,
we obtain a new boson algebra having a shifted vacuum structure and define a
global operatal gauge transformation.Comment: 18 pages, LaTex(run twice), To appear in J. PHys.
Perturbative Symmetries on Noncommutative Spaces
Perturbative deformations of symmetry structures on noncommutative spaces are
studied in view of noncommutative quantum field theories. The rigidity of
enveloping algebras of semi-simple Lie algebras with respect to formal
deformations is reviewed in the context of star products. It is shown that
rigidity of symmetry algebras extends to rigidity of the action of the symmetry
on the space. This implies that the noncommutative spaces considered can be
realized as star products by particular ordering prescriptions which are
compatible with the symmetry. These symmetry preserving ordering prescriptions
are calculated for the quantum plane and four-dimensional quantum Euclidean
space. Using these ordering prescriptions greatly facilitates the construction
of invariant Lagrangians for quantum field theory on noncommutative spaces with
a deformed symmetry.Comment: 16 pages; LaTe
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