3,478 research outputs found
Clan structure analysis and new physics signals in pp collisions at LHC
The study of possible new physics signals in global event properties in pp
collisions in full phase space and in rapidity intervals accessible at LHC is
presented. The main characteristic is the presence of an elbow structure in
final charged particle MD's in addition to the shoulder observed at lower c.m.
energies.Comment: 9 pages, talk given at Focus on Multiplicity (Bari, Italy, June 2004
VLBI observations of nearby radio loud Active Galactic Nuclei
We present an update of the parsec scale properties of the Bologna Complete
Sample consisting of 95 radio sources from the B2 Catalog of Radio Sources and
the Third Cambridge Revised Catalog (3CR), with z < 0.1. Thanks to recent new
data we have now parsec scale images for 76 sources of the sample. Most of them
show a one-sided jet structure but we find a higher fraction of two-sided
sources in comparison with previous flux-limited VLBI surveys. A few peculiar
sources are presented and discussed in more detail.Comment: 6 pages, 7 figures, Proceedings for "The Universe under the
Microscope" (AHAR 2008), April 2008, to be published in Journal of Physics:
Conference Series by Institute of Physics Publishing; R. Schoedel, A. Eckart,
S. Pfalzner, and E. Ros ed
Homogeneous magnetic fields in fully anisotropic string cosmological backgrounds
We present new solutions of the string cosmological effective action in the
presence of a homogeneous Maxwell field with pure magnetic component. Exact
solutions are derived in the case of space-independent dilaton and vanishing
torsion background. In our examples the four dimensional metric is either of
Bianchi-type III and VI or Kantowski-Sachs.Comment: 4 page
Exchange Rate Dynamics with Sticky Prices: The Deutsch Mark, 1974-1982
This paper estimates simultaneously dynamic equations for the Deutsche Mark/Dollar exchange rate and the German wholesale price index, which emerge from a model in which German prices are sticky. This stickiness is due to price adjustment costs which take the form posited by Rotemberg(1982).The main results of the empirical analysis are two: First, the version of the model where prices are perfectly flexible is rejected. Second, real exchange rate variability is mostly accounted for by nominal exchange rate variability. We find substantial overshooting of the exchange rate to monetary innovations like those which appear to be typical in Germany.
Non-topological gravitating defects in five-dimensional anti-de Sitter space
A class of five-dimensional warped solutions is presented. The geometry is
everywhere regular and tends to five-dimensional anti-de Sitter space for large
absolute values of the bulk coordinate. The physical features of the solutions
change depending on the value of an integer parameter. In particular, a set of
solutions describes generalized gravitating kinks where the scalar field
interpolates between two different minima of the potential. The other category
of solutions describes instead gravitating defects where the scalar profile is
always finite and reaches the same constant asymptote both for positive and
negative values of the bulk coordinate. In this sense the profiles are
non-topological. The physical features of the zero modes are discussed.Comment: 9 pages, 4 figure
Characterization of high-dimensional entangled systems via mutually unbiased measurements
Mutually unbiased bases (MUBs) play a key role in many protocols in quantum
science, such as quantum key distribution. However, defining MUBs for arbitrary
high-dimensional systems is theoretically difficult, and measurements in such
bases can be hard to implement. We show experimentally that efficient quantum
state reconstruction of a high-dimensional multi-partite quantum system can be
performed by considering only the MUBs of the individual parts. The state
spaces of the individual subsystems are always smaller than the state space of
the composite system. Thus, the benefit of this method is that MUBs need to be
defined for the small Hilbert spaces of the subsystems rather than for the
large space of the overall system. This becomes especially relevant where the
definition or measurement of MUBs for the overall system is challenging. We
illustrate this approach by implementing measurements for a high-dimensional
system consisting of two photons entangled in the orbital angular momentum
(OAM) degree of freedom, and we reconstruct the state of this system for
dimensions of the individual photons from d=2 to 5.Comment: 8 page
A giant radio halo in the low luminosity X-ray cluster Abell 523
Radio halos are extended and diffuse non-thermal radio sources present at the
cluster center, not obviously associated with any individual galaxy. A strong
correlation has been found between the cluster X-ray luminosity and the halo
radio power. We observe and analyze the diffuse radio emission present in the
complex merging structure Abell 523, classified as a low luminosity X-ray
cluster, to discuss its properties in the context of the halo total radio power
versus X-ray luminosity correlation. We reduced VLA archive observations at 1.4
GHz to derive a deep radio image of the diffuse emission, and compared radio,
optical, and X-ray data. Low-resolution VLA images detect a giant radio halo
associated with a complex merging region. The properties of this new halo agree
with those of radio halos in general discussed in the literature, but its radio
power is about a factor of ten higher than expected on the basis of the cluster
X-ray luminosity. Our study of this giant radio source demonstrates that radio
halos can also be present in clusters with a low X-ray luminosity. Only a few
similar cases have so far been found . This result suggests that this source
represent a new class of objects, that cannot be explained by classical radio
halo models. We suggest that the particle reacceleration related to merging
processes is very efficient and/or the X-ray luminosity is not a good indicator
of the past merging activity of a cluster.Comment: 5 pages, 6 figures, Astronomy and Astrophysics Letter in pres
Comparing the information capacity of entangled Laguerre-Gaussian and Hermite-Gaussian modal sets in a finite-aperture system
Using a spontaneous parametric down-conversion process to create entangled spatial states, we compare the information capacity associated with measurements in the Hermite–Gaussian and Laguerre–Gaussian modal basis in an optical system of finite aperture. We show that the cross-talk imposed by the aperture restriction degrades the information capacity. However, the Laguerre–Gaussian mode measurements show greater resilience to cross talk than the Hermite–Gaussian, suggesting that the Laguerre–Gaussian modal set may still offer real-world advantages over other modal sets
Clan structure analysis and QCD parton showers in multiparticle dynamics. An intriguing dialog between theory and experiment
This paper contains a review of the main results of a search of regularities
in collective variables properties in multiparticle dynamics, regularities
which can be considered as manifestations of the original simplicity suggested
by QCD. The method is based on a continuous dialog between experiment and
theory. The paper follows the development of this research line, from its
beginnings in the seventies to the current state of the art, discussing how it
produced both sound interpretations of the most relevant experimental facts and
intriguing perspectives for new physics signals in the TeV energy domain.Comment: 118 pages, 48 figures; table of contents fixed for hyperre
Fully Anisotropic String Cosmologies, Maxwell Fields and Primordial Shear
We present a class of exact cosmological solutions of the low energy string
effective action in the presence of a homogeneous magnetic fields. We discuss
the physical properties of the obtained (fully anisotropic) cosmologies paying
particular attention to their vacuum limit and to the possible isotropization
mechanisms. We argue that quadratic curvature corrections are able to
isotropize fully anisotropic solutions whose scale factors describe accelerated
expansion. Moreover, the degree of isotropization grows with the duration of
the string phase. We follow the fate of the shear parameter in a decelerated
phase where, dilaton, magnetic fields and radiation fluid are simultaneously
present. In the absence of any magnetic field a long string phase immediately
followed by radiation is able to erase large anisotropies. Conversely, if a
short string phase is followed by a long dilaton dominated phase the
anisotropies can be present, in principle, also at later times. The presence of
magnetic seeds after the end of the string phase can induce further
anisotropies which can be studied within the formalism reported in this paper.Comment: 19 pages in Revtex style, 14 Encapsulated figure
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