35,991 research outputs found
Lorentz Violation and Short-Baseline Neutrino Experiments
A general discussion is given of signals for broken Lorentz symmetry in
short-baseline neutrino experiments. Among the effects that Lorentz violation
can introduce are a dependence on energy differing from that of the usual
massive-neutrino solution and a dependence on the direction of neutrino
propagation. Using the results of the LSND experiment, explicit analysis of the
effects of broken Lorentz symmetry yields a nonzero value (3+/-1) x 10^{-19}
GeV for a combination of coefficients for Lorentz violation. This lies in the
range expected for effects originating from the Planck scale in an underlying
unified theory.Comment: 4 pages REVTe
Ferrimagnetism of MnV_2O_4 spinel
The spinel MnV_2O_4 is a two-sublattice ferrimagnet, with site A occupied by
the Mn^{2+} ion and site B by the V^{3+} ion. The magnon of the system, the
transversal fluctuation of the total magnetization, is a complicated mixture of
the sublattice A and B transversal magnetic fluctuations. As a result, the
magnons' fluctuations suppress in a different way the manganese and vanadium
magnetic orders and one obtains two phases. At low temperature (0,T^*) the
magnetic orders of the Mn and V ions contribute to the magnetization of the
system, while at the high temperature (T^*,T_N), the vanadium magnetic order is
suppressed by magnon fluctuations, and only the manganese ions have non-zero
spontaneous magnetization. A modified spin-wave theory is developed to describe
the two phases and to calculate the magnetization as a function of temperature.
The anomalous curve reproduces the experimentally obtained ZFC
magnetization.Comment: 4 pages, one figur
Linearisable third order ordinary differential equations and generalised Sundman transformations
We calculate in detail the conditions which allow the most general third
order ordinary differential equation to be linearised in X'''(T)=0 under the
transformation X(T)=F(x,t), dT=G(x,t)dt. Further generalisations are
considered.Comment: 33 page
Role of phi decays for K- yields in relativistic heavy-ion collisions
The production of strange mesons in collisions of Ar+KCl at a kinetic beam
energy of 1.756 AGeV is studied within a transport model of
Boltzmann-\"Uhling-Uhlenbeck (BUU) type. In particular, and
yields and spectra are compared to the data mesured recently by the HADES
collaboration and the yield measured previously by the FOPI
collaboration. Our results are in agreement with these data thus presenting an
interpretation of the subleading role of decays into 's and
confirming the importance of the strangeness-exchange channels for
production.Comment: 24 pages, 19 figure
Relativistic theory for time and frequency transfer to order c^{-3}
This paper is motivated by the current development of several space missions
(e.g. ACES on International Space Station) that will fly on Earth orbit laser
cooled atomic clocks, providing a time-keeping accuracy of the order of
5~10^{-17} in fractional frequency. We show that to such accuracy, the theory
of frequency transfer between Earth and Space must be extended from the
currently known relativistic order 1/c^2 (which has been needed in previous
space experiments such as GP-A) to the next relativistic correction of order
1/c^3. We find that the frequency transfer includes the first and second-order
Doppler contributions, the Einstein gravitational red-shift and, at the order
1/c^3, a mixture of these effects. As for the time transfer, it contains the
standard Shapiro time delay, and we present an expression also including the
first and second-order Sagnac corrections. Higher-order relativistic
corrections, at least O(1/c^4), are numerically negligible for time and
frequency transfers in these experiments, being for instance of order 10^{-20}
in fractional frequency. Particular attention is paid to the problem of the
frequency transfer in the two-way experimental configuration. In this case we
find a simple theoretical expression which extends the previous formula (Vessot
et al. 1980) to the next order 1/c^3. In the Appendix we present the detailed
proofs of all the formulas which will be needed in such experiments.Comment: 11 pages, 2 figures, to appear in Astronomy & Astrophysic
Recommended from our members
Texas Business Review, October 1976
To Push or Not To Push; Tracking Intracity Changes; Killeen-Temple: Magnet AreaBureau of Business Researc
The orbital elements and physical properties of the eclipsing binary BD+36 3317, a probable member of Lyr cluster
Context. The fact that eclipsing binaries belong to a stellar group is
useful, because the former can be used to estimate distance and additional
properties of the latter, and vice versa. Aims. Our goal is to analyse new
spectroscopic observations of BD along with the photometric
observations from the literature and, for the first time, to derive all basic
physical properties of this binary. We aim to find out whether the binary is
indeed a member of the Lyr open cluster. Methods. The spectra were
reduced using the IRAF program and the radial velocities were measured with the
program SPEFO. The line spectra of both components were disentangled with the
program KOREL and compared to a grid of synthetic spectra. The final combined
radial-velocity and photometric solution was obtained with the program PHOEBE.
Results. We obtained the following physical elements of BD: , , , , ,
. We derived the effective temperatures
K, K. Both components
are located close to ZAMS in the Hertzsprung-Russell (HR) diagram and their
masses and radii are consistent with the predictions of stellar evolutionary
models. Our results imply the average distance to the system d = pc.
We re-investigated the membership of BD in the Lyr
cluster and confirmed it. The distance to BD, given above,
therefore represents an accurate estimate of the true distance for Lyr
cluster. Conclusions. The reality of the Lyr cluster and the cluster
membership of BD have been reinforced.Comment: 10 pages, 7 figures. Accepted for publication in A&
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