132,842 research outputs found

### A tensor-vector-scalar framework for modified dynamics and cosmic dark matter

I describe a tensor-vector-scalar theory that reconciles the galaxy scale
success of modified Newtonian dynamics (MOND) with the cosmological scale
evidence for CDM. The theory provides a cosmological basis for MOND in the
sense that the predicted phenomenology only arises in a cosmological
background. The theory contains an evolving effective potential, and scalar
field oscillations in this potential comprise the cold dark matter; the de
Broglie wavelength of these soft bosons, however, is sufficiently large that
they cannot accumulate in galaxies. The theory predicts, inevitably, a constant
anomalous acceleration in the outer solar system which, depending upon the
choice of parameters, can be consistent with that detected by the Pioneer
spacecrafts.Comment: minor corrections, numerical error corrected in eq. 37 and subsequent
equations, accepted MNRA

### Transitions to Measure Synchronization in Coupled Hamiltonian Systems

Transitions to measure synchronization in two coupled $\phi ^{4}$ lattices
are investigated based on numerical simulations. The relationship between
measure synchronization (MS), phase locking and system's total energy is
studied both for periodic and chaotic states. Two different scalings are
discovered during the process to MS according to phase locking. Random walk
like phase synchronization in chaotic measure synchronization is found, and
phase locking interrupted by phase slips irregularly is also investigated.
Meanwhile, related analysis is qualitative given to explain this phenomenon.Comment: 10 pages, 6 figure

### Observation of a single atom in a magneto-optical trap

Fluorescence from Cs atoms in a magneto-optical trap is detected under conditions of very low atomic density. Discrete steps are observed in the fluorescent signal versus time and are associated with the arrival and departure of individual trapped atoms. Histograms of the frequency of occurrence of a given level of fluorescence exhibit a series of uniformly spaced peaks that are attributed to the presence of N = 0, 1, 2 atoms in the trap

### Recent advances on recursive filtering and sliding mode design for networked nonlinear stochastic systems: A survey

Copyright © 2013 Jun Hu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Some recent advances on the recursive filtering and sliding mode design problems for nonlinear stochastic systems with network-induced phenomena are surveyed. The network-induced phenomena under consideration mainly include missing measurements, fading measurements, signal quantization, probabilistic sensor delays, sensor saturations, randomly occurring nonlinearities, and randomly occurring uncertainties. With respect to these network-induced phenomena, the developments on filtering and sliding mode design problems are systematically reviewed. In particular, concerning the network-induced phenomena, some recent results on the recursive filtering for time-varying nonlinear stochastic systems and sliding mode design for time-invariant nonlinear stochastic systems are given, respectively. Finally, conclusions are proposed and some potential future research works are pointed out.This work was supported in part by the National Natural Science Foundation of China under Grant nos. 61134009, 61329301, 61333012, 61374127 and 11301118, the Engineering and Physical Sciences Research Council (EPSRC) of the UK under Grant no. GR/S27658/01, the Royal Society of the UK, and the Alexander von Humboldt Foundation of Germany

### Wigner functions of thermo number state, photon subtracted and added thermo vacuum state at finite temperature

Based on Takahashi-Umezawa thermo field dynamics and the order-invariance of
Weyl ordered operators under similar transformations, we present a new approach
to deriving the exact Wigner functions of thermo number state, photon
subtracted and added thermo vacuum state. We find that these Wigner functions
are related to the Gaussian-Laguerre type functions of temperature, whose
statistical properties are then analysed.Comment: 10 pages and 2 figure

### Stress-energy Tensor Correlators in N-dim Hot Flat Spaces via the Generalized Zeta-Function Method

We calculate the expectation values of the stress-energy bitensor defined at
two different spacetime points $x, x'$ of a massless, minimally coupled scalar
field with respect to a quantum state at finite temperature $T$ in a flat
$N$-dimensional spacetime by means of the generalized zeta-function method.
These correlators, also known as the noise kernels, give the fluctuations of
energy and momentum density of a quantum field which are essential for the
investigation of the physical effects of negative energy density in certain
spacetimes or quantum states. They also act as the sources of the
Einstein-Langevin equations in stochastic gravity which one can solve for the
dynamics of metric fluctuations as in spacetime foams. In terms of
constitutions these correlators are one rung above (in the sense of the
correlation -- BBGKY or Schwinger-Dyson -- hierarchies) the mean (vacuum and
thermal expectation) values of the stress-energy tensor which drive the
semiclassical Einstein equation in semiclassical gravity. The low and the high
temperature expansions of these correlators are also given here: At low
temperatures, the leading order temperature dependence goes like $T^{N}$ while
at high temperatures they have a $T^{2}$ dependence with the subleading terms
exponentially suppressed by $e^{-T}$. We also discuss the singular behaviors of
the correlators in the $x'\rightarrow x$ coincident limit as was done before
for massless conformal quantum fields.Comment: 23 pages, no figures. Invited contribution to a Special Issue of
Journal of Physics A in honor of Prof. J. S. Dowke

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