92,441 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
Quantum mechanical photon-count formula derived by entangled state representation
By introducing the thermo entangled state representation, we derived four new
photocount distribution formulas for a given density operator of light field.
It is shown that these new formulas, which is convenient to calculate the
photocount, can be expressed as such integrations over Laguree-Gaussian
function with characteristic function, Wigner function, Q-function, and
P-function, respectively.Comment: 5 pages, no figur
Nonequilibrium Dynamics of Charged Particles in an Electromagnetic Field: Causal and Stable Dynamics from 1/c Expansion of QED
We derive from a microscopic Hamiltonian a set of stochastic equations of
motion for a system of spinless charged particles in an electromagnetic (EM)
field based on a consistent application of a dimensionful 1/c expansion of
quantum electrodynamics (QED). All relativistic corrections up to order 1/c^3
are captured by the dynamics, which includes electrostatic interactions
(Coulomb), magnetostatic backreaction (Biot-Savart), dissipative backreaction
(Abraham-Lorentz) and quantum field fluctuations at zero and finite
temperatures. With self-consistent backreaction of the EM field included we
show that this approach yields causal and runaway-free equations of motion,
provides new insights into charged particle backreaction, and naturally leads
to equations consistent with the (classical) Darwin Hamiltonian and has quantum
operator ordering consistent with the Breit Hamiltonian. To order 1/c^3 the
approach leads to a nonstandard mass renormalization which is associated with
magnetostatic self-interactions, and no cutoff is required to prevent runaways.
Our new results also show that the pathologies of the standard Abraham-Lorentz
equations can be seen as a consequence of applying an inconsistent (i.e.
incomplete, mixed-order) expansion in 1/c, if, from the start, the analysis is
viewed as generating a low-energy effective theory rather than an exact
solution. Finally, we show that the 1/c expansion within a Hamiltonian
framework yields well-behaved noise and dissipation, in addition to the
multiple-particle interactions.Comment: 17 pages, 2 figure
Response of YBCO/PCBO/YBCO ramp type Josephson junctions to near MM wave irradiation
A high Tc Josephson device for high frequency detection applications is being developed, consisting of an YBCO/PBCO/YBCO ramp type junction and a broad band log-periodic antenna. In this contribution we present the response of such a device to (near) mm wave irradiation. Shapiro steps have been observed up to very high voltage values - nearly 4 mV at 10 K, at the maximum of the radiation power. The modulation of the step amplitudes shows very good resemblence with the predictions from the Resistively Shunted Junction model
The Universal Edge Physics in Fractional Quantum Hall Liquids
The chiral Luttinger liquid theory for fractional quantum Hall edge transport
predicts universal power-law behavior in the current-voltage (-)
characteristics for electrons tunneling into the edge. However, it has not been
unambiguously observed in experiments in two-dimensional electron gases based
on GaAs/GaAlAs heterostructures or quantum wells. One plausible cause is the
fractional quantum Hall edge reconstruction, which introduces non-chiral edge
modes. The coupling between counterpropagating edge modes can modify the
exponent of the - characteristics. By comparing the fractional
quantum Hall states in modulation-doped semiconductor devices and in graphene
devices, we show that the graphene-based systems have an experimental
accessible parameter region to avoid the edge reconstruction, which is suitable
for the exploration of the universal edge tunneling exponent predicted by the
chiral Luttinger liquid theory.Comment: 7 pages, 6 figure
Polynomial loss of memory for maps of the interval with a neutral fixed point
We give an example of a sequential dynamical system consisting of
intermittent-type maps which exhibits loss of memory with a polynomial rate of
decay. A uniform bound holds for the upper rate of memory loss. The maps may be
chosen in any sequence, and the bound holds for all compositions.Comment: 16 page
Generalized thermo vacuum state derived by the partial trace method
By virtue of the technique of integration within an ordered product (IWOP) of
operators we present a new approach for deriving generalized thermo vacuum
state which is simpler in form that the result by using the Umezawa-Takahashi
approach, in this way the thermo field dynamics can be developed. Applications
of the new state are discussed.Comment: 5 pages, no figure, revtex
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