3,949 research outputs found
Euclidean Thermal Green Functions of Photons in Generalized Euclidean Rindler Spaces for any Feynman-like Gauge
The thermal Euclidean Green functions for Photons propagating in the Rindler
wedge are computed employing an Euclidean approach within any covariant
Feynman-like gauge. This is done by generalizing a formula which holds in the
Minkowskian case. The coincidence of the found (\be=2\pi)-Green functions and
the corresponding Minkowskian vacuum Green functions is discussed in relation
to the remaining static gauge ambiguity already found in previous papers.
Further generalizations to more complicated manifolds are discussed. Ward
identities are verified in the general case.Comment: 12 pages, standard latex, no figures, some signs changed, more
comments added, final version to appear on Int. J. Mod. Phys.
Bell inequality violation by entangled single photon states generated from a laser, a LED or a Halogen lamp
In single-particle or intraparticle entanglement, two degrees of freedom of a
single particle, e.g., momentum and polarization of a single photon, are
entangled. Single-particle entanglement (SPE) provides a source of non
classical correlations which can be exploited both in quantum communication
protocols and in experimental tests of noncontextuality based on the
Kochen-Specker theorem. Furthermore, SPE is robust under decoherence phenomena.
Here, we show that single-particle entangled states of single photons can be
produced from attenuated sources of light, even classical ones. To
experimentally certify the entanglement, we perform a Bell test, observing a
violation of the Clauser, Horne, Shimony and Holt (CHSH) inequality. On the one
hand, we show that this entanglement can be achieved even in a classical light
beam, provided that first-order coherence is maintained between the degrees of
freedom involved in the entanglement. On the other hand, we prove that filtered
and attenuated light sources provide a flux of independent SPE photons that,
from a statistical point of view, are indistinguishable from those generated by
a single photon source. This has important consequences, since it demonstrates
that cheap, compact, and low power entangled photon sources can be used for a
range of quantum technology applications
Continuous slice functional calculus in quaternionic Hilbert spaces
The aim of this work is to define a continuous functional calculus in
quaternionic Hilbert spaces, starting from basic issues regarding the notion of
spherical spectrum of a normal operator. As properties of the spherical
spectrum suggest, the class of continuous functions to consider in this setting
is the one of slice quaternionic functions. Slice functions generalize the
concept of slice regular function, which comprises power series with
quaternionic coefficients on one side and that can be seen as an effective
generalization to quaternions of holomorphic functions of one complex variable.
The notion of slice function allows to introduce suitable classes of real,
complex and quaternionic --algebras and to define, on each of these
--algebras, a functional calculus for quaternionic normal operators. In
particular, we establish several versions of the spectral map theorem. Some of
the results are proved also for unbounded operators. However, the mentioned
continuous functional calculi are defined only for bounded normal operators.
Some comments on the physical significance of our work are included.Comment: 71 pages, some references added. Accepted for publication in Reviews
in Mathematical Physic
States of co-existence and border projects in port cities: Genoa and Rotterdam compared
In port cities there is a tendency to dislocate production activities in favour of logistic-productive dynamics. In addition, the transition from an industrial area model to a \u2018logistics hinterland\u2019 formula shifts attention to a territorial scale, focusing on spaces at the border between the port and city areas. Today, port\u2013city borders are commonly perceived as barriers but they could be dynamic development thresholds. Existing port cities exhibit different states of coexistence at their port\u2013city borders: sometimes they are forced situations originating from poor management, but they can also provide opportunities for mutual interaction and synergy. This paper compares port\u2013 city borders in Genoa and Rotterdam using interviews, relevant literature and mapping. Conclusions are drawn concerning the possibilities and potential for future port\u2013city borders
Single muscle fiber proteomics reveals unexpected mitochondrial specialization
Mammalian skeletal muscles are composed of multinucleated cells termed slow or fast fibers according to their contractile and metabolic properties. Here, we developed a high-sensitivity workflow to characterize the proteome of single fibers. Analysis of segments of the same fiber by traditional and unbiased proteomics methods yielded the same subtype assignment. We discovered novel subtype-specific features, most prominently mitochondrial specialization of fiber types in substrate utilization. The fiber type-resolved proteomes can be applied to a variety of physiological and pathological conditions and illustrate the utility of single cell type analysis for dissecting proteomic heterogeneity
A Bisognano-Wichmann-like Theorem in a Certain Case of a Non Bifurcate Event Horizon related to an Extreme Reissner-Nordstr\"om Black Hole
Thermal Wightman functions of a massless scalar field are studied within the
framework of a ``near horizon'' static background model of an extremal R-N
black hole. This model is built up by using global Carter-like coordinates over
an infinite set of Bertotti-Robinson submanifolds glued together. The
analytical extendibility beyond the horizon is imposed as constraints on
(thermal) Wightman's functions defined on a Bertotti-Robinson sub manifold. It
turns out that only the Bertotti-Robinson vacuum state, i.e. , satisfies
the above requirement. Furthermore the extension of this state onto the whole
manifold is proved to coincide exactly with the vacuum state in the global
Carter-like coordinates. Hence a theorem similar to Bisognano-Wichmann theorem
for the Minkowski space-time in terms of Wightman functions holds with
vanishing ``Unruh-Rindler temperature''. Furtermore, the Carter-like vacuum
restricted to a Bertotti-Robinson region, resulting a pure state there, has
vanishing entropy despite of the presence of event horizons. Some comments on
the real extreme R-N black hole are given
Higgs signals and hard photons at the Next Linear Collider: the -fusion channel in the Standard Model
In this paper, we extend the analyses carried out in a previous article for
-fusion to the case of Higgs production via -fusion within the Standard
Model at the Next Linear Collider, in presence of electromagnetic radiation due
real photon emission. Calculations are carried out at tree-level and rates of
the leading order (LO) processes e^+e^-\rightarrow e^+e^- H \ar e^+e^- b\bar b
and e^+e^-\rightarrow e^+e^- H \ar e^+e^- WW \ar e^+e^- \mathrm{jjjj} are
compared to those of the next-to-leading order (NLO) reactions
e^+e^-\rightarrow e^+e^- H (\gamma)\ar e^+e^- b\bar b \gamma and
e^+e^-\rightarrow e^+e^- H (\gamma)\ar e^+e^- WW (\gamma) \ar e^+e^-
\mathrm{jjjj}\gamma, in the case of energetic and isolated photons.Comment: 12 pages, LaTeX, 5 PostScript figures embedded using epsfig and
bitmapped at 100dpi, complete paper including high definition figures
available at ftp://axpa.hep.phy.cam.ac.uk/stefano/cavendish_9611.ps or at
http://www.hep.phy.cam.ac.uk/theory/papers
Wightman Functions' Behaviour on the Event Horizon of an Extremal Reissner-Nordstr\"om Black Hole
A weaker Haag, Narnhofer and Stein prescription as well as a weaker Hessling
Quantum Equivalence Principle for the behaviour of thermal Wightman functions
on an event horizon are analysed in the case of an extremal
Reissner-Nordstr\"{o}m black hole in the limit of a large mass. In order to
avoid the degeneracy of the metric in the stationary coordinates on the
horizon, a method is introduced which employs the invariant length of geodesics
which pass the horizon. First the method is checked for a massless scalar field
on the event horizon of the Rindler wedge, extending the original procedure of
Haag, Narnhofer and Stein onto the {\em whole horizon} and recovering the same
results found by Hessling. Afterwards the HNS prescription and Hessling's
prescription for a massless scalar field are analysed on the whole horizon of
an extremal Reissner-Nordstr\"{o}m black hole in the limit of a large mass. It
is proved that the weak form of the HNS prescription is satisfyed for all the
finite values of the temperature of the KMS states, i.e., this principle does
not determine any Hawking temperature. It is found that the
Reissner-Nordstr\"{o}m vacuum, i.e., does satisfy the weak HNS
prescription and it is the only state which satisfies weak Hessling's
prescription, too. Finally, it is suggested that all the previously obtained
results should be valid dropping the requirements of a massless field and of a
large mass black hole.Comment: 27 pages, standard LaTex, no figures, final version containing the
results following from Hessling's principle as they appeared in the other
paper gr-qc/9510016, minor changes in the text and in references, it will
appear on Class. Quant. Gra
FONESYS and SILENCE Networks: Looking to the Future of T-H Code Development and Experimentation
The purpose of this paper is to present briefly the projects called FONESYS (Forum &
Network of System Thermal-Hydraulics Codes in Nuclear Reactor Thermal-Hydraulics) and
SILENCE (Significant Light and Heavy Water Reactor Thermal Hydraulic Experiments
Network for the Consistent Exploitation of the Data), their participants, their motivations,
their main targets and working modalities.
System Thermal-Hydraulics (SYS-TH) codes, also as part of the Best Estimate Plus
Uncertainty (BEPU) approaches, are expected to achieve a more-and-more relevant role in
nuclear reactor safety and design technology. Namely, the number of code-users is likely to
increase in the countries where nuclear technology is exploited. Thus, the idea of establishing
a forum and a network among the code developers and with possible extension to code users
has started to have major importance and value. In this framework, the FONESYS initiative
has been launched in 2010 aiming at creation of a common ground for discussing current
limitations and envisaged improvements in various areas of SYS-TH and their application in
the licensing process and safety analysis.
According to FONESYS statute, there are seven signatory Institutions and two observer
Institutions currently participating in the project. Signatory Institutions are AREVA-NP,
Commissariat à l’Énergie Atomique et aux Énergies Alternatives (CEA), San Piero a Grado
Nuclear Research Group - University of Pisa (GRNSPG-UNIPI), Gesellschaft für Anlagenund
Reaktorsicherheit (GRS), Korea Atomic Energy Research Institute (KAERI), Korea
Institute of Nuclear Safety (KINS), and VTT Technical Research Centre of Finland.
SILENCE is a network that intends to promote the cooperation among teams of
experimentalists managing or involved in significant experimental projects in nuclear reactor
thermal-hydraulics, with the aim to contrast the risk of losing expertise and vision in this
important area of the nuclear technology. This network was launched in 2012, replicating for
the TH experimental domain the role that FONESYS plays in the code-development domain.
Currently, the following Organizations are Members of SILENCE: AREVA GmbH,
Helmholtz Zentrum Dresden-Rossendorf (HZDR), Korea Atomic Energy Research Institute
(KAERI), Hungarian Academy of Sciences Centre for Energy Research (MTA EK),Lappeenranta University of Technology (LUT), and Paul Scherrer Institute (PSI). SILENCE
is currently organizing a “Specialists Workshop on Advanced Instrumentation and
Measurement Techniques for Nuclear Reactor Thermal Hydraulics” (SWINTH-2016).
The San Piero a Grado Nuclear Research Group - University of Pisa (GRNSPG-UNIPI)
is the Host Institution and plays as a Scientific Secretariat for both Networks
Accurate early positions for Swift GRBS: enhancing X-ray positions with UVOT astrometry
Here we describe an autonomous way of producing more accurate prompt XRT
positions for Swift-detected GRBs and their afterglows, based on UVOT
astrometry and a detailed mapping between the XRT and UVOT detectors. The
latter significantly reduces the dominant systematic error -- the star-tracker
solution to the World Coordinate System. This technique, which is limited to
times when there is significant overlap between UVOT and XRT PC-mode data,
provides a factor of 2 improvement in the localisation of XRT refined positions
on timescales of less than a few hours. Furthermore, the accuracy achieved is
superior to astrometrically corrected XRT PC mode images at early times (for up
to 24 hours), for the majority of bursts, and is comparable to the accuracy
achieved by astrometrically corrected X-ray positions based on deep XRT PC-mode
imaging at later times (abridged).Comment: 12 pages, 8 figures, 1 table, submitted to Astronomy and
Astrophysics, August 7th 200
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