13,339 research outputs found
Surfaces with prescribed Weingarten-Operator
We investigate pairs of surfaces in Euclidean 3-space with the same Weingarten operator in case that one surface is given as surface of revolution. Our local and global results complement global results on ovaloids of revolution from [S-V-W-W]
Left-Handed W Bosons at the LHC
The production of W bosons in association with jets is an important
background to new physics at the LHC. Events in which the W carries large
transverse momentum and decays leptonically lead to large missing energy and
are of particular importance. We show that the left-handed nature of the W
coupling, combined with valence quark domination at a pp machine, leads to a
large left-handed polarization for both W^+ and W^- bosons at large transverse
momenta. The polarization fractions are very stable with respect to QCD
corrections. The leptonic decay of the W bosons translates the common
left-handed polarization into a strong asymmetry in transverse momentum
distributions between positrons and electrons, and between neutrinos and
anti-neutrinos (missing transverse energy). Such asymmetries may provide an
effective experimental handle on separating W + jets from top quark production,
which exhibits very little asymmetry due to C invariance, and from various
types of new physics.Comment: 32 pages, revtex, 17 figures, 3 tables, v2 minor corrections to ME+PS
results, no changes to conclusions, added reference
Titan's magnetic field signature during the Cassini T34 flyby: Comparison between hybrid simulations and MAG data
During the T34 flyby on 19 July 2007, the Cassini spacecraft passed through the magnetic pile-up region at Titan's ramside. The magnetic environment of Titan during this flyby is studied using a three-dimensional hybrid simulation model. This approach treats the electrons of the plasma as a massless, charge-neutralizing fluid, whereas the effects of finite ion gyroradii are taken into account by modeling the ions as individual particles. The simulation results are compared to data collected by the Cassini Magnetometer Instrument. The key features of the measured magnetic field signature have shown to be fully reproducible in the framework of the simulation model. Several signatures in the observed magnetic field can be ascribed to the passage of the Cassini spacecraft through the magnetic barrier upstream of Titan.Fil: Simon, S.. Technische Universitat Braunschweig; AlemaniaFil: Motschmann, U.. Technische Universitat Braunschweig; AlemaniaFil: Kleindienst, G.. Technische Universitat Braunschweig; AlemaniaFil: Glassmeier, K. H.. Technische Universitat Braunschweig; AlemaniaFil: Bertucci, Cesar. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Dougherty, M. K.. Imperial College London; Reino Unid
Tzitz\'eica transformation is a dressing action
We classify the simplest rational elements in a twisted loop group, and prove
that dressing actions of them on proper indefinite affine spheres give the
classical Tzitz\'eica transformation and its dual. We also give the group point
of view of the Permutability Theorem, construct complex Tzitz\'eica
transformations, and discuss the group structure for these transformations
The structure of hot gas in Cepheus B
By observing radiation-affected gas in the Cepheus B molecular cloud we probe
whether the sequential star formation in this source is triggered by the
radiation from newly formed stars. We used the dual band receiver GREAT onboard
SOFIA to map [C II] and CO 13--12 and 11--10 in Cep B and compared the spatial
distribution and the spectral profiles with complementary ground-based data of
low- transitions of CO isotopes, atomic carbon, and the radio continuum. The
interaction of the radiation from the neighboring OB association creates a
large photon-dominated region (PDR) at the surface of the molecular cloud
traced through the photoevaporation of C^+. Bright internal PDRs of hot gas are
created around the embedded young stars, where we detect evidence of the
compression of material and local velocity changes; however, on the global
scale we find no indications that the dense molecular material is dynamically
affected.Comment: Accepted for publication in A&A (SOFIA/GREAT special issue
Experimental characterization of frequency dependent squeezed light
We report on the demonstration of broadband squeezed laser beams that show a
frequency dependent orientation of the squeezing ellipse. Carrier frequency as
well as quadrature angle were stably locked to a reference laser beam at
1064nm. This frequency dependent squeezing was characterized in terms of noise
power spectra and contour plots of Wigner functions. The later were measured by
quantum state tomography. Our tomograph allowed a stable lock to a local
oscillator beam for arbitrary quadrature angles with one degree precision.
Frequency dependent orientations of the squeezing ellipse are necessary for
squeezed states of light to provide a broadband sensitivity improvement in
third generation gravitational wave interferometers. We consider the
application of our system to long baseline interferometers such as a future
squeezed light upgraded GEO600 detector.Comment: 8 pages, 8 figure
(In)finiteness of Spherically Symmetric Static Perfect Fluids
This work is concerned with the finiteness problem for static, spherically
symmetric perfect fluids in both Newtonian Gravity and General Relativity. We
derive criteria on the barotropic equation of state guaranteeing that the
corresponding perfect fluid solutions possess finite/infinite extent. In the
Newtonian case, for the large class of monotonic equations of state, and in
General Relativity we improve earlier results
Macroscopic superpositions via nested interferometry: finite temperature and decoherence considerations
Recently there has been much interest in optomechanical devices for the
production of macroscopic quantum states. Here we focus on a proposed scheme
for achieving macroscopic superpositions via nested interferometry. We consider
the effects of finite temperature on the superposition produced. We also
investigate in detail the scheme's feasibility for probing various novel
decoherence mechanisms.Comment: 12 pages, 2 figure
Gaussian Wigner distributions and hierarchies of nonclassical states in quantum optics-The single mode case
A recently introduced hierarchy of states of a single mode quantised
radiation field is examined for the case of centered Guassian Wigner
distributions. It is found that the onset of squeezing among such states
signals the transition to the strongly nonclassical regime. Interesting
consequences for the photon number distribution, and explicit representations
for them, are presented.Comment: 11 Pages Revtex one eps figure. Replaced with minor changes in ref
Orbits and phase transitions in the multifractal spectrum
We consider the one dimensional classical Ising model in a symmetric
dichotomous random field. The problem is reduced to a random iterated function
system for an effective field. The D_q-spectrum of the invariant measure of
this effective field exhibits a sharp drop of all D_q with q < 0 at some
critical strength of the random field. We introduce the concept of orbits which
naturally group the points of the support of the invariant measure. We then
show that the pointwise dimension at all points of an orbit has the same value
and calculate it for a class of periodic orbits and their so-called offshoots
as well as for generic orbits in the non-overlapping case. The sharp drop in
the D_q-spectrum is analytically explained by a drastic change of the scaling
properties of the measure near the points of a certain periodic orbit at a
critical strength of the random field which is explicitly given. A similar
drastic change near the points of a special family of periodic orbits explains
a second, hitherto unnoticed transition in the D_q-spectrum. As it turns out, a
decisive role in this mechanism is played by a specific offshoot. We
furthermore give rigorous upper and/or lower bounds on all D_q in a wide
parameter range. In most cases the numerically obtained D_q coincide with
either the upper or the lower bound. The results in this paper are relevant for
the understanding of random iterated function systems in the case of moderate
overlap in which periodic orbits with weak singularity can play a decisive
role.Comment: The article has been completely rewritten; the title has changed; a
section about the typical pointwise dimension as well as several references
and remarks about more general systems have been added; to appear in J. Phys.
A; 25 pages, 11 figures, LaTeX2
- …