936,818 research outputs found
About quantum fluctuations and holographic principle in (4+n)-dimensional spacetime
In the article we present explicit expressions for quantum fluctuations of
spacetime in the case of -dimensional spacetimes, and consider their
holographic properties and some implications for clocks, black holes and
computation. We also consider quantum fluctuations and their holographic
properties in ADD model and estimate the typical size and mass of the clock to
be used in precise measurements of spacetime fluctuations. Numerical
estimations of phase incoherence of light from extra-galactic sources in ADD
model are also presented.Comment: 5 page
Weak-Light, Zero to -\pi Lossless Kerr-Phase Gate in Quantum-well System via Tunneling Interference Effect
We examine a Kerr phase gate in a semiconductor quantum well structure based
on the tunnelling interference effect. We show that there exist a specific
signal field detuning, at which the absorption/amplification of the probe field
will be eliminated with the increase of the tunnelling interference.
Simultaneously, the probe field will acquire a -\pi phase shift at the exit of
the medium. We demonstrate with numerical simulations that a complete 180^\circ
phase rotation for the probe field at the exit of the medium is achieved, which
may result in many applications in information science and telecommunication
A feasible algorithm for typing in Elementary Affine Logic
We give a new type inference algorithm for typing lambda-terms in Elementary
Affine Logic (EAL), which is motivated by applications to complexity and
optimal reduction. Following previous references on this topic, the variant of
EAL type system we consider (denoted EAL*) is a variant without sharing and
without polymorphism. Our algorithm improves over the ones already known in
that it offers a better complexity bound: if a simple type derivation for the
term t is given our algorithm performs EAL* type inference in polynomial time.Comment: 20 page
A mechanism for preseismic steady rupture fronts observed in laboratory experiments
It has been shown that the onset of frictional instability is characterized by a transition from stable, quasi-static rupture growth to unstable, inertially-controlled high-speed rupture. In particular, slow rupture fronts propagating at a steady speed V_(slow) of the order of 5% of the S-wave speed have been observed prior to the onset of dynamic rupture in recent fault-friction laboratory experiments. However, the precise mechanism governing this V_(slow) stage is unknown. Here we reproduce this phenomenon in numerical simulations of earthquake sequences that incorporate laboratory-derived rate-and-state friction laws. Our simulations show that the V_(slow) stage originates from a stress concentration inherited from the coalescence of interseismic slow creep fronts. Its occurrence is limited to a narrow range of the parameter space but is found in simulations with two commonly-used state-variable evolution laws in the rate-and-state formulation. The sensitivity of the speed V_(slow) to the model parameters suggests that the propagation speed V_(slow) reported in laboratory experiments may also be sensitive to parameters of friction and stress conditions. Our results imply that time and space dimensions associated with the propagation of V_(slow) on natural faults can be as much as a few seconds and several hundred meters, respectively. Hence the detection of such preseismic signals may be possible with near-field high-resolution observations
Physics of computation and light sheet concept in the measurement of (4+n)-dimensional spacetime geometry
We analyze the limits that quantum mechanics imposes on the accuracy to which
-dimensional spacetime geometry can be measured. Using physics of
computation and light sheet concept we derive explicit expressions for quantum
fluctuations and explore their cumulative effects for various spacetime foam
models.Comment: 5 page
The density profile of equilibrium and non-equilibrium dark matter halos
We study the diversity of the density profiles of dark matter halos based on
a large set of high-resolution cosmological simulations of 256^3 particles. The
cosmological models include four scale-free models and three representative
cold dark matter models. The simulations have good force resolution, and there
are about 400 massive halos with more than 10^4 particles within the virial
radius in each cosmological model. Our unbiased selection of all massive halos
enables to quantify how well the bulk of dark matter halos can be described by
the Navarro, Frenk & White (NFW) profile which was established for equilibrium
halos. We find that about seventy percent of the halos can be fitted by the NFW
profile with a fitting residual dvi_{max} less than 30% in Omega_0=1 universes.
This percentage is higher in lower density cosmological models. The rest of the
halos exhibits larger deviations from the NFW profile for more significant
internal substructures. There is a considerable amount of variation in the
density profile even for the halos which can be fitted by the NFW profile (i.e.
dvi_{max}<0.30). The distribution of the profile parameter, the concentration
, can be well described by a lognormal function with the mean value \bar c
slightly smaller (15%) than the NFW result and the dispersion \sigma_c in \ln c
about 0.25. The more virialized halos with dvi_{max}<0.15 have the mean value
\bar c in good agreement with the NFW result and a slightly smaller dispersion
\sigma_c (about 0.2). Our results can alleviate some of the conflicts found
recently between the theoretical NFW profile and observational results.
Implications for theoretical and observational studies of galaxy formation are
discussed.Comment: The final version accepted for publication in ApJ; one figure and one
paragraph added to demonstrate that all the conclusions of the first version
are solid to the resoltuion effects; 19 pages with 6 figure
A model of a dual-core matter-wave soliton laser
We propose a system which can generate a periodic array of solitary-wave
pulses from a finite reservoir of coherent Bose-Einstein condensate (BEC). The
system is built as a set of two parallel quasi-one-dimensional traps (the
reservoir proper and a pulse-generating cavity), which are linearly coupled by
the tunneling of atoms. The scattering length is tuned to be negative and small
in the absolute value in the cavity, and still smaller but positive in the
reservoir. Additionally, a parabolic potential profile is created around the
center of the cavity. Both edges of the reservoir and one edge of the cavity
are impenetrable. Solitons are released through the other cavity's edge, which
is semi-transparent. Two different regimes of the intrinsic operation of the
laser are identified: circulations of a narrow wave-function pulse in the
cavity, and oscillations of a broad standing pulse. The latter regime is
stable, readily providing for the generation of an array containing up to
10,000 permanent-shape pulses. The circulation regime provides for no more than
40 cycles, and then it transforms into the oscillation mode. The dependence of
the dynamical regime on parameters of the system is investigated in detail.Comment: Journal of Physics B, in pres
- âŠ