1,227 research outputs found
Foundations of a spacetime path formalism for relativistic quantum mechanics
Quantum field theory is the traditional solution to the problems inherent in
melding quantum mechanics with special relativity. However, it has also long
been known that an alternative first-quantized formulation can be given for
relativistic quantum mechanics, based on the parametrized paths of particles in
spacetime. Because time is treated similarly to the three space coordinates,
rather than as an evolution parameter, such a spacetime approach has proved
particularly useful in the study of quantum gravity and cosmology. This paper
shows how a spacetime path formalism can be considered to arise naturally from
the fundamental principles of the Born probability rule, superposition, and
Poincar\'e invariance. The resulting formalism can be seen as a foundation for
a number of previous parametrized approaches in the literature, relating, in
particular, "off-shell" theories to traditional on-shell quantum field theory.
It reproduces the results of perturbative quantum field theory for free and
interacting particles, but provides intriguing possibilities for a natural
program for regularization and renormalization. Further, an important
consequence of the formalism is that a clear probabilistic interpretation can
be maintained throughout, with a natural reduction to non-relativistic quantum
mechanics.Comment: RevTex 4, 42 pages; V6 is as accepted for publication in the Journal
of Mathematical Physics, updated in response to referee comments; V7 includes
final editorial correction
Electromagnetic filaments and edge modifications induced by electrode biasing in the RFX-mod tokamak
Detection of the BL Lac object 1ES1426+428 in the Very High Energy gamma-ray band by the CAT Telescope from 1998-2000
The BL Lac Object 1ES 1426+428, at a red-shift of z=0.129, has been monitored
by the CAT telescope from February 1998 to June 2000. The accumulation of 26
hours of observations shows a gamma-ray signal of 321 events above 250 GeV at
5.2 standard deviations, determined using data analysis cuts adapted to a weak,
steep-spectrum source. The source emission has an average flux of Phi_diff(400
GeV) = 6.73 +/- 1.27stat +/- 1.45syst x 10^-11 /cm^-2/s/TeV, and a very steep
spectrum, with a differential spectral index of gamma = -3.60 +/- 0.57 which
can be refined to gamma = -3.66 +/- 0.41 using a higher flux data subset. If,
as expected from its broad-band properties, the Very High Energy emission is
hard at the source, these observations support a strong absorption effect of
gamma-rays by the Intergalactic Infrared field.Comment: 4 pages, 3 figures, accepted for publication in A&A Letter
A Mach-Zehnder interferometer based on orbital angular momentum for improved vortex coronagraph efficiency
The Annular Groove Phase Mask (AGPM) is a vectorial vortex phase mask. It acts as a half-wave plate with a radial fast axis orientation operating in the mid infrared domain. When placed at the focus of a telescope element provides a continuous helical phase ramp for an on axis sources, which creates the orbital angular momentum. Thanks to that phase, the intensity of the central source is canceled by a down-stream pupil stop, while the off axis sources are not affected. However due to experimental conditions the nulling is hardly perfect. To improve the null, a Mach-Zehnder interferometer containing Dove prisms differently oriented can be proposed to sort out light based on its orbital angular momentum (OAM). Thanks to the differential rotation of the beam, a π phase shift is achieved for the on axis light affected by a non zero OAM. Therefore the contrast between the star and its faint companion is enhanced. Nevertheless, due the Dove prisms birefringence, the performance of the interferometer is relatively poor. To solve this problem, we propose to add a birefringent wave-plate in each arm to compensate this birefringence. In this paper, we will develop the mathematical model of the wave front using the Jones formalism. The performance of the interferometer is at first computed for the simple version without the birefringent plate. Then the effect of the birefringent plate is be mathematically described and the performance is re-computed
Physical propositions and quantum languages
The word \textit{proposition} is used in physics with different meanings,
which must be distinguished to avoid interpretational problems. We construct
two languages and with classical
set-theoretical semantics which allow us to illustrate those meanings and to
show that the non-Boolean lattice of propositions of quantum logic (QL) can be
obtained by selecting a subset of \textit{p-testable} propositions within the
Boolean lattice of all propositions associated with sentences of
. Yet, the aforesaid semantics is incompatible with the
standard interpretation of quantum mechanics (QM) because of known no-go
theorems. But if one accepts our criticism of these theorems and the ensuing SR
(semantic realism) interpretation of QM, the incompatibility disappears, and
the classical and quantum notions of truth can coexist, since they refer to
different metalinguistic concepts (\textit{truth} and \textit{verifiability
according to QM}, respectively). Moreover one can construct a quantum language
whose Lindenbaum-Tarski algebra is isomorphic to QL, the
sentences of which state (testable) properties of individual samples of
physical systems, while standard QL does not bear this interpretation.Comment: 15 pages, no figure, standard Late
Complex Spectral Variability from Intensive Multi-wavelength Monitoring of Mrk421 in 1998
We conducted a multi-frequency campaign for the TeV blazar Mrk~421 in 1998
April. The campaign started from a pronounced high amplitude flare recorded by
SAX and Whipple; ASCA observation started three days later. In the X-ray data,
we detected multiple flares, occuring on time scales of about one day. ASCA
data clearly reveal spectral variability. The comparison of the data from ASCA,
EUVE and RXTE indicates that the variability amplitudes in the low energy
synchrotron component are larger at higher photon energies. In TeV Gamma-rays,
large intra-day variations -- which were correlated with the X-ray flux -- were
observed when results from three Cherenkov telescopes are combined. The RMS
variability of TeV Gamma--rays was similar to that observed in hard X-rays,
above 10 keV. The X-ray light curve reveals flares which are almost symmetric
for most of cases, implying the dominant time scale is the light crossing time
through the emitting region. The structure function analysis based on the
continuous X-ray light curve of seven days indicates that the characteristic
time scale is ~0.5 day. The analysis of ASCA light curves in various energy
bands appears to show both soft (positive) and hard (negative) lags. These may
not be real, as systematic effects could also produce these lags, which are all
much smaller than an orbit. If the lags of both signs are real, these imply
that the particle acceleration and X-ray cooling time scales are similar.Comment: 10 pages, 4 figures, accepted for publication in ApJ Letter
Information-theoretic principle entails orthomodularity of a lattice
Quantum logical axiomatic systems for quantum theory usually include a
postulate that a lattice under consideration is orthomodular. We propose a
derivation of orthomodularity from an information-theoretic axiom. This
provides conceptual clarity and removes a long-standing puzzle about the
meaning of orthomodularity.Comment: Version prior to published, with slight modification
High energy photon flux prediction from neutralino annihilation in the globular cluster Palomar 13
The distant globular cluster Palomar 13 has been found to have a very high
mass-to-light ratio and its profile can be well fitted either by a King model
with a tail, or with a NFW model. This cluster may be the first case of the
many clumps predicted by CDM simulations that would not be disrupted by the
galactic halo potential. We make the hypothesis that Pal 13 is made of
neutralinos and run the DarkSuspect code to estimate the high-energy photon
flux due to the annihilation of neutralinos through various channels in some
benchmark scenarios. These low fluxes may be used as targets to be reached in
proposals for future ground-based high altitude Cerenkov telescopes.Comment: A 2-page poster to be published in ``Astronomy, Cosmology and
Fundamental Physics'', the proceedings of the ESO-CERN-ESA Symposium, eds. P.
A. Shaver, L. Di Lella, and A. Gimene
Very High Energy Gamma-ray spectral properties of Mrk 501 from CAT Cerenkov telescope observations in 1997
The BL Lac object Mrk 501 went into a very high state of activity during
1997, both in VHE gamma-rays and X-rays. We present here results from
observations at energies above 250 GeV carried out between March and October
1997 with the CAT Cerenkov imaging Telescope. The average differential spectrum
between 30 GeV and 13 TeV shows significant curvature and is well represented
by phi_0 * E_TeV^{-(alpha + beta*log10(E_TeV))}, with: phi_0 = 5.19 +/- 0.13
{stat} +/- 0.12 {sys-MC} +1.66/-1.04 {sys-atm} * 10^-11 /cm^2/s/TeV alpha =
2.24 +/- 0.04 {stat} +/- 0.05 {sys} beta = 0.50 +/- 0.07 {stat} (negligible
systematics). The TeV spectral energy distribution of Mrk 501 clearly peaks in
the range 500 GeV-1 TeV. Investigation of spectral variations shows a
significant hardness-intensity correlation with no measurable effect on the
curvature. This can be described as an increase of the peak TeV emission energy
with intensity. Simultaneous and quasi-simultaneous CAT VHE gamma-ray and
BeppoSAX hard X-ray detections for the highest recorded flare on 16th April and
for lower-activity states of the same period show correlated variability with a
higher luminosity in X-rays than in gamma-rays. The observed spectral energy
distribution and the correlated variability between X-rays and gamma-rays, both
in amplitude and in hardening of spectra, favour a two-component emission
scheme where the low and high energy components are attributed to synchrotron
and inverse Compton (IC) radiation, respectively.Comment: Submitted to Astronomy and Astrophysics, 8 pages including 6 figures.
Published with minor change
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