3,039 research outputs found

### Transport of the repulsive Bose-Einstein condensate in a double-well trap: interaction impact and relation to Josephson effect

Two aspects of the transport of the repulsive Bose-Einstein condensate (BEC)
in a double-well trap are inspected: impact of the interatomic interaction and
analogy to the Josephson effect. The analysis employs a numerical solution of
3D time-dependent Gross-Pitaevskii equation for a total order parameter
covering all the trap. The population transfer is driven by a time-dependent
shift of a barrier separating the left and right wells. Sharp and soft profiles
of the barrier velocity are tested. Evolution of the relevant characteristics,
involving phase differences and currents, is inspected. It is shown that the
repulsive interaction substantially supports the transfer making it possible i)
in a wide velocity interval and ii) three orders of magnitude faster than in
the ideal BEC. The transport can be approximately treated as the d.c. Josephson
effect. A dual origin of the critical barrier velocity (break of adiabatic
following and d.c.-a.c. transition) is discussed. Following the calculations,
robustness of the transport (d.c.) crucially depends on the interaction and
barrier velocity profile. Only soft profiles which minimize undesirable dipole
oscillations are acceptable.Comment: 10 pages, 8 figures, accepted by Laser Physis. arXiv admin note: text
overlap with arXiv:1312.2750 The replaced version has a few corrections and
additional reference

### First Passage Time of Filtered Poisson Process with Exponential Shape Function

Solving some integro-differential equation we find the Laplace transformation of the first passage time for Filtered Poisson Process generated by pulses with uniform or exponential distributions. Also, the martingale technique is applied for approximations of expectations accuracy is veryfying with the help of Monte-Carlo simulations.first passage times; laplace transformation; martingales; integro-differential equations; filtered poisson process; ornstein-uhlenbeck process

### Once more on extra quark-lepton generations and precision measurements

Precision measurements of $Z$-boson parameters and $W$-boson and $t$-quark
masses put strong constraints on non $SU(2)\times U(1)$ singlet New Physics. We
demonstrate that one extra generation passes electroweak constraints even when
all new particle masses are well above their direct mass bounds.Comment: Dedicated to L.B. Okun's 80th birthda

### Peculiarities of anisotropy and polarization as an indicator of noises in the CMB maps

We discuss some new problems of the modern cosmology which arose after the
BOOMERANG and MAXIMA-1 successful missions. Statistics of high peaks of the CMB
anisotropy is analyzed and we discuss possible inner structure of such peaks in
the observational data of future MAP and PLANCK missions. We have investigated
geometrical and statistical properties of the CMB polarization around such high
isolated peaks of anisotropy in the presence of a polarized pixel noise and
point sources. The structure of polarization fields in the vicinity of singular
points with zero polarization is very sensitive to the level of pixel noises
and point sources in the CMB maps.Comment: 9 pages, 2 figure

### Towards the use of the most massive black hole candidates in AGN to test the Kerr paradigm

The super-massive objects in galactic nuclei are thought to be the Kerr black
holes predicted by General Relativity, although a definite proof of their
actual nature is still lacking. The most massive objects in AGN ($M \sim 10^9
M_\odot$) seem to have a high radiative efficiency ($\eta \sim 0.4$) and a
moderate mass accretion rate ($L_{\rm bol}/L_{\rm Edd} \sim 0.3$). The high
radiative efficiency could suggest they are very rapidly-rotating black holes.
The moderate luminosity could indicate that their accretion disk is
geometrically thin. If so, these objects could be excellent candidates to test
the Kerr black hole hypothesis. An accurate measurement of the radiative
efficiency of an individual AGN may probe the geometry of the space-time around
the black hole candidate with a precision comparable to the one achievable with
future space-based gravitational-wave detectors like LISA. A robust evidence of
the existence of a black hole candidate with $\eta > 0.32$ and accreting from a
thin disk may be interpreted as an indication of new physics. For the time
being, there are several issues to address before using AGN to test the Kerr
paradigm, but the approach seems to be promising and capable of providing
interesting results before the advent of gravitational wave astronomy.Comment: 12 pages, 6 figures. v2: some typos correcte

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