464 research outputs found
Gravitational scalar field coupled directly to the Maxwell field and its effect to solar-system experiments
The effect of the massless gravitational scalar field assumed to couple
directly to the Maxwell field to the solar-system experiments is estimated. We
start with discussing the theoretical significances of this coupling. Rather
disappointingly, however, we find that the scalar-field parameters never affect
the observation in the limit of the geometric optics, indicating a marked
difference from the well-known contribution through the spacetime metric.Comment: LaTex 10 page
ALMA CO Observations of Supernova Remnant N63A in the Large Magellanic Cloud: Discovery of Dense Molecular Clouds Embedded within Shock-Ionized and Photoionized Nebulae
We carried out new CO( = 1-0, 3-2) observations of a N63A supernova
remnant (SNR) from the LMC using ALMA and ASTE. We find three giant molecular
clouds toward the northeast, east, and near the center of the SNR. Using the
ALMA data, we spatially resolved clumpy molecular clouds embedded within the
optical nebulae in both the shock-ionized and photoionized lobes discovered by
previous H and [S II] observations. The total mass of the molecular
clouds is for the shock-ionized region and
for the photoionized region. Spatially resolved X-ray spectroscopy
reveals that the absorbing column densities toward the molecular clouds are
- cm, which are - times less
than the averaged interstellar proton column densities for each region. This
means that the X-rays are produced not only behind the molecular clouds, but
also in front of them. We conclude that the dense molecular clouds have been
completely engulfed by the shock waves, but have still survived erosion owing
to their high-density and short interacting time. The X-ray spectrum toward the
gas clumps is well explained by an absorbed power-law or high-temperature
plasma models in addition to the thermal plasma components, implying that the
shock-cloud interaction is efficiently working for both the cases through the
shock ionization and magnetic field amplification. If the hadronic gamma-ray is
dominant in the GeV band, the total energy of cosmic-ray protons is calculated
to be - erg with the estimated ISM proton density
of cm, containing both the shock-ionized gas and
neutral atomic hydrogen.Comment: 18 pages, 4 tables, 8 figures, accepted for publication in The
Astrophysical Journal (ApJ
Nonlinear electrodynamics and the Pioneer 10/11 spacecraft anomaly
The occurrence of the phenomenon known as photon acceleration is a natural
prediction of nonlinear electrodynamics (NLED). This would appear as an
anomalous frequency shift in any modeling of the electromagnetic field that
only takes into account the classical Maxwell theory. Thus, it is tempting to
address the unresolved anomalous, steady; but time-dependent, blueshift of the
Pioneer 10/11 spacecrafts within the framework of NLED. Here we show that
astrophysical data on the strength of the magnetic field in both the Galaxy and
the local (super)cluster of galaxies support the view on the major Pioneer
anomaly as a consequence of the phenomenon of photon acceleration. If
confirmed, through further observations or lab experiments, the reality of this
phenomenon should prompt to take it into account in any forthcoming research on
both cosmological evolution and origin and dynamical effects of primordial
magnetic fields, whose seeds are estimated to be very weak.Comment: Final version accepted for publication in Europhysics Letters, uses
EPL style, 7 page
Resonance Kondo Tunneling through a Double Quantum Dot at Finite Bias
It is shown that the resonance Kondo tunneling through a double quantum dot
(DQD) with even occupation and singlet ground state may arise at a strong bias,
which compensates the energy of singlet/triplet excitation. Using the
renormalization group technique we derive scaling equations and calculate the
differential conductance as a function of an auxiliary dc-bias for parallel DQD
described by SO(4) symmetry. We analyze the decoherence effects associated with
the triplet/singlet relaxation in DQD and discuss the shape of differential
conductance line as a function of dc-bias and temperature.Comment: 11 pages, 6 eps figures include
Anisotropic Brane Cosmology with Variable and
In this work, the cosmological implications of brane world scenario are
investigated when the gravitational coupling and the cosmological term
are not constant but rather there are time variation of them. From
observational point of view, these time variations are taken in the form
and . The behavior of scale
factors and different kinematical parameters are investigated for different
possible scenarios where the bulk cosmological constant can be
zero, positive or negative.Comment: RevTex, 7 figures, 16 page
Photo-production of neutral kaons on 12C in the threshold region
Kaon photo-production process on C has been studied by measuring
neutral kaons in a photon energy range of 0.81.1 GeV. Neutral kaons were
identified by the invariant mass constructed from two charged pions emitted in
the decay channel. The differential cross sections
as well as the integrated ones in the threshold photon energy region were
obtained. The obtained momentum spectra were compared with a Spectator model
calculation using elementary amplitudes of kaon photo-production given by
recent isobar models. Present result provides, for the first time, the
information on reaction which is expected to play an
important role to construct models for strangeness production by the
electromagnetic interaction. Experimental results show that cross section of
is of the same order to that of and suggest that slightly backward angular distribution
is favored in the process.Comment: 6 pages, 8 figure
On the triad transfer analysis of plasma turbulence : symmetrization, coarse graining, and directional representation
This article discusses triad transfer analysis via quadratic nonlinearity. To avoid fictitious interactions, symmetrization of the triad transfer is reviewed, including arbitrary orthogonal decomposition and coarse graining. The directional representation of the symmetrized triad transfer is proposed by minimizing the number of edges in a network graph of triad interactions with keeping the energy consistency. The directional representation simplifies visualization and allows us to reduce the energy transfer into a one-to-one relation, while eliminating fictitious interactions in non-symmetrized triad transfer functions. Energy transfer processes among plasma turbulent fluctuations that decompose by the singular value decomposition are analyzed as an application. A network graph visualization clearly demonstrates the importance of symmetrization and the consistency between the symmetrized triad transfer and its directional representation
Kondo effect in systems with dynamical symmetries
This paper is devoted to a systematic exposure of the Kondo physics in
quantum dots for which the low energy spin excitations consist of a few
different spin multiplets . Under certain conditions (to be
explained below) some of the lowest energy levels are nearly
degenerate. The dot in its ground state cannot then be regarded as a simple
quantum top in the sense that beside its spin operator other dot (vector)
operators are needed (in order to fully determine its quantum
states), which have non-zero matrix elements between states of different spin
multiplets . These "Runge-Lenz"
operators do not appear in the isolated dot-Hamiltonian (so in some sense they
are "hidden"). Yet, they are exposed when tunneling between dot and leads is
switched on. The effective spin Hamiltonian which couples the metallic electron
spin with the operators of the dot then contains new exchange terms,
beside the ubiquitous ones . The operators and generate a
dynamical group (usually SO(n)). Remarkably, the value of can be controlled
by gate voltages, indicating that abstract concepts such as dynamical symmetry
groups are experimentally realizable. Moreover, when an external magnetic field
is applied then, under favorable circumstances, the exchange interaction
involves solely the Runge-Lenz operators and the corresponding
dynamical symmetry group is SU(n). For example, the celebrated group SU(3) is
realized in triple quantum dot with four electrons.Comment: 24 two-column page
- …