6,756 research outputs found
Nonlinear stability of the Taub-NUT soliton in 6+1 dimensions
Using mixed numerical and analytical methods we give evidence that the 6+1
dimensional Taub-NUT soliton is asymptotically nonlinearly stable against small
perturbations preserving biaxial Bianchi IX symmetry. We also show that for
sufficiently strong perturbations the soliton collapses to a warped black hole.
Since this black hole solution is not known in closed form, for completeness of
the exposition we prove its existence and determine its properties. In
particular, the mass of the black hole is computed.Comment: 19 pages, 5 figure
Photovoltaic system test facility electromagnetic interference measurements
Field strength measurements on a single row of panels indicates that the operational mode of the array as configured presents no radiated EMI problems. Only one relatively significant frequency band near 200 kHz showed any degree of intensity (9 muV/m including a background level of 5 muV/m). The level was measured very near the array (at 20 ft distance) while Federal Communications Commission (FCC) regulations limit spurious emissions to 15 muV/m at 1,000 ft. No field strength readings could be obtained even at 35 ft distant
Parameters for Twisted Representations
The study of Hermitian forms on a real reductive group gives rise, in the
unequal rank case, to a new class of Kazhdan-Lusztig-Vogan polynomials. These
are associated with an outer automorphism of , and are related to
representations of the extended group . These polynomials were
defined geometrically by Lusztig and Vogan in "Quasisplit Hecke Algebras and
Symmetric Spaces", Duke Math. J. 163 (2014), 983--1034. In order to use their
results to compute the polynomials, one needs to describe explicitly the
extension of representations to the extended group. This paper analyzes these
extensions, and thereby gives a complete algorithm for computing the
polynomials. This algorithm is being implemented in the Atlas of Lie Groups and
Representations software
Scalar Field Theory on Non-commutative Snyder Space-Time
We construct a scalar field theory on the Snyder non-commutative space-time.
The symmetry underlying the Snyder geometry is deformed at the co-algebraic
level only, while its Poincar\'e algebra is undeformed. The Lorentz sector is
undeformed at both algebraic and co-algebraic level, but the co-product for
momenta (defining the star-product) is non-co-associative. The Snyder-deformed
Poincar\'e group is described by a non-co-associative Hopf algebra. The
definition of the interacting theory in terms of a non-associative star-product
is thus questionable. We avoid the non-associativity by the use of a space-time
picture based on the concept of realization of a non-commutative geometry. The
two main results we obtain are: (i) the generic (namely for any realization)
construction of the co-algebraic sector underlying the Snyder geometry and (ii)
the definition of a non-ambiguous self interacting scalar field theory on this
space-time. The first order correction terms of the corresponding Lagrangian
are explicitly computed. The possibility to derive Noether charges for the
Snyder space-time is also discussed.Comment: 10 pages; v2: introduction rewritten, co-algebraic analysis improved,
references added; to appear in PR
Extended Poincar\'e supersymmetry in three dimensions and supersymmetric anyons
We classify the unitary representations of the extended Poincar\'e
supergroups in three dimensions. Irreducible unitary representations of any
spin can appear, which correspond to supersymmetric anyons. Our results also
show that all irreducible unitary representations necessarily have physical
momenta. This is in sharp contrast to the ordinary Poincar\'e group in three
dimensions, that admits in addition irreducible unitary representations with
non-physical momenta, which are discarded on physical grounds.Comment: 7 pages; commentaries added in Sect. IV A and in Conclusion; added
reference
Equivalence of domains for hyperbolic Hubbard-Stratonovich transformations
We settle a long standing issue concerning the traditional derivation of
non-compact non-linear sigma models in the theory of disordered electron
systems: the hyperbolic Hubbard-Stratonovich (HS) transformation of
Pruisken-Schaefer type. Only recently the validity of such transformations was
proved in the case of U(p,q) (non-compact unitary) and O(p,q) (non-compact
orthogonal) symmetry. In this article we give a proof for general non-compact
symmetry groups. Moreover we show that the Pruisken-Schaefer type
transformations are related to other variants of the HS transformation by
deformation of the domain of integration. In particular we clarify the origin
of surprising sign factors which were recently discovered in the case of
orthogonal symmetry.Comment: 30 pages, 3 figure
Lie series for celestial mechanics, accelerators, satellite stabilization and optimization
Lie series applications to celestial mechanics, accelerators, satellite orbits, and optimizatio
The Cold and Hot Gas Content of Fine-Structure E and S0 Galaxies
We investigate trends of the cold and hot gas content of early-type galaxies
with the presence of optical morphological peculiarities, as measured by the
fine-structure index (Sigma). HI mapping observations from the literature are
used to track the cold-gas content, and archival ROSAT PSPC data are used to
quantify the hot-gas content. We find that E and S0 galaxies with a high
incidence of optical peculiarities are exclusively X-ray underluminous and,
therefore, deficient in hot gas. In contrast, more relaxed galaxies with little
or no signs of optical peculiarities span a wide range of X-ray luminosities.
That is, the X-ray excess anticorrelates with Sigma. There appears to be no
similar trend of cold-gas content with either fine-structure index or X-ray
content. The fact that only apparently relaxed E and S0 galaxies are strong
X-ray emitters is consistent with the hypothesis that after strong disturbances
such as a merger hot-gas halos build up over a time scale of several gigayears.
This is consistent with the expected mass loss from stars.Comment: 12 pages, latex, 5 figures. Accepted for publication in A
Theory of nuclear excitation by electron capture for heavy ions
We investigate the resonant process of nuclear excitation by electron
capture, in which a continuum electron is captured into a bound state of an ion
with the simultaneous excitation of the nucleus. In order to derive the cross
section a Feshbach projection operator formalism is introduced. Nuclear states
and transitions are described by a nuclear collective model and making use of
experimental data. Transition rates and total cross sections for NEEC followed
by the radiative decay of the excited nucleus are calculated for various heavy
ion collision systems
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