31,122 research outputs found
Supersymmetric features of the Maxwell fish-eye lens
We provide a supersymmetric analysis of the Maxwell fisheye (MF) wave problem
at zero energy. Working in the so-called sector, we obtain the
corresponding superpartner (fermionic) MF effective potential within Witten's
one-dimensional (radial) supersymmetric procedure.Comment: 5 pages in Latex, one figure not included has been published as Fig.
2 in Phys. Lett. A 208 (1995) 33-3
Nonparametric detection using extreme-value theory
Nonparametric extreme value statistics for constant signal detection in additive nois
Time-dependent Schr\"odinger equations having isomorphic symmetry algebras. I. Classes of interrelated equations
In this paper, we focus on a general class of Schr\"odinger equations that
are time-dependent and quadratic in X and P. We transform Schr\"odinger
equations in this class, via a class of time-dependent mass equations, to a
class of solvable time-dependent oscillator equations. This transformation
consists of a unitary transformation and a change in the ``time'' variable. We
derive mathematical constraints forthe transformation and introduce two
examples.Comment: LaTeX, 18 pages, new format, edite
Kaon production and propagation at intermediate relativistic energies
We systematically study observables in nucleus-nucleus collisions at
1-2 A GeV within the Boltzmann-Uehling-Uhlenbeck (BUU) transport model. We
compare our calculations with the KaoS data on the kaon multiplicities and
spectra. In addition, the kaon collective flow is computed and compared with
the FOPI and KaoS data. We show, that the elliptic kaon flow measured recently
by the KaoS Collaboration is best described by using the Brown-Rho
parametrization of the kaon potential ( MeV).Comment: 21 pages, 3 tables, 17 figures; references added; version accepted in
PR
A constructive algorithm for the Cartan decomposition of SU(2^N)
We present an explicit numerical method to obtain the Cartan-Khaneja-Glaser
decomposition of a general element G of SU(2^N) in terms of its `Cartan' and
`non-Cartan' components. This effectively factors G in terms of group elements
that belong in SU(2^n) with n<N, a procedure that can be iterated down to n=2.
We show that every step reduces to solving the zeros of a matrix polynomial,
obtained by truncation of the Baker-Campbell-Hausdorff formula, numerically.
All computational tasks involved are straightforward and the overall truncation
errors are well under control.Comment: 15 pages, no figures, matlab file at
http://cam.qubit.org/users/jiannis
3-D Models of Embedded High-Mass Stars: Effects of a Clumpy Circumstellar Medium
We use 3-D radiative transfer models to show the effects of clumpy
circumstellar material on the observed infrared colors of high mass stars
embedded in molecular clouds. We highlight differences between 3-D clumpy and
1-D smooth models which can affect the interpretation of data. We discuss
several important properties of the emergent spectral energy distribution
(SED): More near-infrared light (scattered and direct from the central source)
can escape than in smooth 1-D models. The near- and mid-infrared SED of the
same object can vary significantly with viewing angle, depending on the clump
geometry along the sightline. Even the wavelength-integrated flux can vary with
angle by more than a factor of two. Objects with the same average circumstellar
dust distribution can have very different near-and mid-IR SEDs depending on the
clump geometry and the proximity of the most massive clump to the central
source.
Although clumpiness can cause similar objects to have very different SEDs,
there are some observable trends. Near- and mid-infrared colors are sensitive
to the weighted average distance of clumps from the central source and to the
magnitude of clumpy density variations (smooth-to-clumpy ratio). Far-infrared
emission remains a robust measure of the total dust mass. We present simulated
SEDs, colors, and images for 2MASS and Spitzer filters. We compare to
observations of some UCHII regions and find that 3-D clumpy models fit better
than smooth models. In particular, clumpy models with fractal dimensions in the
range 2.3-2.8, smooth to clumpy ratios of <50%, and density distributions with
shallow average radial density profiles fit the SEDs best.Comment: accepted to ApJ; version with full-res figures:
http://www.astro.virginia.edu/~ri3e/clumpy3d.pd
Anomalous Lattice Response at the Mott Transition in a Quasi-2D Organic Conductor
Discontinuous changes of the lattice parameters at the Mott metal-insulator
transition are detected by high-resolution dilatometry on deuterated crystals
of the layered organic conductor -(BEDT-TTF)Cu[N(CN)]Br.
The uniaxial expansivities uncover a striking and unexpected anisotropy,
notably a zero-effect along the in-plane c-axis along which the electronic
interactions are relatively strong. A huge thermal expansion anomaly is
observed near the end-point of the first-order transition line enabling to
explore the critical behavior with very high sensitivity. The analysis yields
critical fluctuations with an exponent 0.8 0.15
at odds with the novel criticality recently proposed for these materials
[Kagawa \textit{et al.}, Nature \textbf{436}, 534 (2005)]. Our data suggest an
intricate role of the lattice degrees of freedom in the Mott transition for the
present materials.Comment: 4 pages, 4 figure
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