6,953 research outputs found
Testing Single-Parameter Classical Standpoint Cosmology
Experimental tests of homogeneous-universe classical standpoint cosmology are
proposed after presentation of conceptual considerations that encourage this
radical departure from the standard model. Among predictions of the new model
are standpoint age equal to Hubble time, energy-density parameter , and relations between redshift, Hubble-scale distribution of
matter and galaxy luminosity and angular diameter. These latter relations
coincide with those of the standard model for zero deceleration. With eye to
further tests, geodesics of the non-Riemannian standpoint metric are explicitly
given. Although a detailed thermodynamic ``youthful-standpoint'' approximation
remains to be developed (for particle mean free path small on standpoint
scale), standpoint temperature depending only on standpoint age is a natural
concept, paralleling energy density and redshift that perpetuates thermal
spectrum for cosmic background radiation. Prospects for primordial
nucleosynthesis are promising.Comment: 27 pages, latexed, math_macros.tex used, full postscript available
from: http://theor1.lbl.gov/www/theorgroup/papers/37162.p
Weak Classical-Gravity Source in Standpoint Cosmology
Guided by a linearized approximation to Einstein theory, an interim
prescription for ``weak source of gravity'' - - in ``particle'' energy-momentum
distributed along standpoint light cone - - is formulated for (classical)
standpoint cosmology.Comment: 11 pages, uses math_macros.tex, late
Phase-locking at low-level of quanta
We discuss phase-locking phenomena at low-level of quanta for parametrically
driven nonlinear Kerr resonator (PDNR) in strong quantum regime. Oscillatory
mode of PDNR is created in the process of a degenerate down-conversion of
photons under interaction with a train of external Gaussian pulses. We
calculate the Wigner functions of cavity mode showing two-fold symmetry in
phase space and analyse formation of phase-locked states in the regular as well
as the quantum chaotic regime.Comment: 6 pages, 4 figure
Regional Indexes of Activity: Combining the Old with the New
This paper proposes a framework to construct indexes of activity which links two strands of the index literature – the traditional business cycle analysis and the latent variable approach. To illustrate the method, we apply the framework to Australian regional data, namely to two resource-rich and two service-based states. The results reveal differences in the evolution and drivers of economic activity across the four states. We also demonstrate the value of the Index in a broader context by using a structural vector autoregression (SVAR) approach to analyse the effects of shocks from the US and from China. This Index-SVAR approach facilitates a richer analysis because the unique feature of the index method proposed here allows impulse responses to be traced back to the components.Regional economic activity, coincident indicators, dynamic latent factor model
High-Resolution Spectroscopy during Eclipse of the Young Substellar Eclipsing Binary 2MASS 0535-0546. II. Secondary Spectrum: No Evidence that Spots Cause the Temperature Reversal
We present high-resolution optical spectra of the young brown-dwarf eclipsing
binary 2M0535-05, obtained during eclipse of the higher-mass (primary) brown
dwarf. Combined with our previous spectrum of the primary alone (Paper I), the
new observations yield the spectrum of the secondary alone. We investigate,
through a differential analysis of the two binary components, whether cool
surface spots are responsible for suppressing the temperature of the primary.
In Paper I, we found a significant discrepancy between the empirical surface
gravity of the primary and that inferred via fine analysis of its spectrum.
Here we find precisely the same discrepancy in surface gravity, both
qualitatively and quantitatively. While this may again be ascribed to either
cool spots or model opacity errors, it implies that cool spots cannot be
responsible for preferentially lowering the temperature of the primary: if they
were, spot effects on the primary spectrum should be preferentially larger, and
they are not. The Teff we infer for the primary and secondary, from the
TiO-epsilon bands alone, show the same reversal, in the same ratio, as is
empirically observed, bolstering the validity of our analysis. In turn, this
implies that if suppression of convection by magnetic fields on the primary is
the fundamental cause of the Teff reversal, then it cannot be a local
suppression yielding spots mainly on the primary (though both components may be
equally spotted), but a global suppression in the interior of the primary. We
briefly discuss current theories of how this might work.Comment: Final ApJ version. Small textual change in summary at the end (Sec
6.2), to include work published after submission of this paper; no changes in
our results or conclusion
Exploring the S-Matrix of Massless Particles
We use the recently proposed generalised on-shell representation for
scattering amplitudes and a consistency test to explore the space of tree-level
consistent couplings in four-dimensional Minkowski spacetime. The extension of
the constructible notion implied by the generalised on-shell representation,
i.e. the possibility to reconstruct at tree level all the scattering amplitudes
from the three-particle ones, together with the imposition of the consistency
conditions at four-particle level, allow to rediscover all the known theories
and their algebra structure, if any. Interestingly, this analysis seems to
leave room for high-spin couplings, provided that at least the requirement of
locality is weakened. We do not claim to have found tree-level consistent
high-spin theories, but rather that our methods show signatures of them and
very likely, with a suitable modification, they can be a good framework to
perform a systematic search.Comment: 44 pages, 1 figur
Bistability and chaos at low-level of quanta
We study nonlinear phenomena of bistability and chaos at a level of few
quanta. For this purpose we consider a single-mode dissipative oscillator with
strong Kerr nonlinearity with respect to dissipation rate driven by a
monochromatic force as well as by a train of Gaussian pulses. The quantum
effects and decoherence in oscillatory mode are investigated on the framework
of the purity of states and the Wigner functions calculated from the master
equation. We demonstrate the quantum chaotic regime by means of a comparison
between the contour plots of the Wigner functions and the strange attractors on
the classical Poincar\'e section. Considering bistability at low-limit of
quanta, we analyze what is the minimal level of excitation numbers at which the
bistable regime of the system is displayed? We also discuss the formation of
oscillatory chaotic regime by varying oscillatory excitation numbers at ranges
of few quanta. We demonstrate quantum-interference phenomena that are assisted
hysteresis-cycle behavior and quantum chaos for the oscillator driven by the
train of Gaussian pulses as well as we establish the border of
classical-quantum correspondence for chaotic regimes in the case of strong
nonlinearities.Comment: 10 pages, 14 figure
Transition from collisionless to collisional MRI
Recent calculations by Quataert et al. (2002) found that the growth rates of
the magnetorotational instability (MRI) in a collisionless plasma can differ
significantly from those calculated using MHD. This can be important in hot
accretion flows around compact objects. In this paper we study the transition
from the collisionless kinetic regime to the collisional MHD regime, mapping
out the dependence of the MRI growth rate on collisionality. A kinetic closure
scheme for a magnetized plasma is used that includes the effect of collisions
via a BGK operator. The transition to MHD occurs as the mean free path becomes
short compared to the parallel wavelength 2\pi/k_{\Par}. In the weak magnetic
field regime where the Alfv\'en and MRI frequencies are small compared
to the sound wave frequency k_{\Par} c_0, the dynamics are still effectively
collisionless even if , so long as the collision frequency \nu
\ll k_{\Par} c_{0}; for an accretion flow this requires \nu \lsim \Omega
\sqrt{\beta}. The low collisionality regime not only modifies the MRI growth
rate, but also introduces collisionless Landau or Barnes damping of long
wavelength modes, which may be important for the nonlinear saturation of the
MRI.Comment: 20 pages, 4 figures, submitted to ApJ with a clearer derivation of
anisotropic pressure closure from drift kinetic equatio
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