2,985 research outputs found
Superdiffusion of massive particles induced by multi-scale velocity fields
We study drag-induced diffusion of massive particles in scale-free velocity
fields, where superdiffusive behavior emerges due to the scale-free size
distribution of the vortices of the underlying velocity field. The results show
qualitative resemblance to what is observed in fluid systems, namely the
diffusive exponent for the mean square separation of pairs of particles and the
preferential concentration of the particles, both as a function of the response
time.Comment: 5 pages, 5 figures. Accepted for publication in EP
Development of engineering solutions for air drilling at Dulisminsk oilfield, Irkutsk oblast
The article presents the analysis of disastrous mud loss achieved during casing at Dulisminsk oil and gas condensate field (DOGCF) and comparative evaluation of geological structure of DOGCF and Naryksko-Ostashkinsk area of Kemerovo oblast, where the same problem was solved successfully. On the basis of the analysis, an engineering solution is proposed to prevent mud loss in the conditions of DOGCF
Stochastic Loewner evolution driven by Levy processes
Standard stochastic Loewner evolution (SLE) is driven by a continuous
Brownian motion, which then produces a continuous fractal trace. If jumps are
added to the driving function, the trace branches. We consider a generalized
SLE driven by a superposition of a Brownian motion and a stable Levy process.
The situation is defined by the usual SLE parameter, , as well as
which defines the shape of the stable Levy distribution. The resulting
behavior is characterized by two descriptors: , the probability that the
trace self-intersects, and , the probability that it will approach
arbitrarily close to doing so. Using Dynkin's formula, these descriptors are
shown to change qualitatively and singularly at critical values of and
. It is reasonable to call such changes ``phase transitions''. These
transitions occur as passes through four (a well-known result) and as
passes through one (a new result). Numerical simulations are then used
to explore the associated touching and near-touching events.Comment: Published version, minor typos corrected, added reference
Quasigroups, Asymptotic Symmetries and Conservation Laws in General Relativity
A new quasigroup approach to conservation laws in general relativity is
applied to study asymptotically flat at future null infinity spacetime. The
infinite-parametric Newman-Unti group of asymptotic symmetries is reduced to
the Poincar\'e quasigroup and the Noether charge associated with any element of
the Poincar\'e quasialgebra is defined. The integral conserved quantities of
energy-momentum and angular momentum are linear on generators of Poincar\'e
quasigroup, free of the supertranslation ambiguity, posess the flux and
identically equal to zero in Minkowski spacetime.Comment: RevTeX4, 5 page
Iron and s-elements abundance variations in NGC5286: comparison with anomalous globular clusters and Milky Way satellites
We present a high resolution spectroscopic analysis of 62 red giants in the
Milky Way globular cluster NGC5286. We have determined abundances of
representative light proton-capture, alpha, Fe-peak and neutron-capture element
groups, and combined them with photometry of multiple sequences observed along
the colour-magnitude diagram. Our principal results are: (i) a broad, bimodal
distribution in s-process element abundance ratios, with two main groups, the
s-poor and s-rich groups; (ii) substantial star-to-star Fe variations, with the
s-rich stars having higher Fe, e.g. _s-rich - _s-poor ~
0.2~dex; and (iii) the presence of O-Na-Al (anti-)correlations in both stellar
groups. We have defined a new photometric index, c_{BVI}=(B-V)-(V-I), to
maximise the separation in the colour-magnitude diagram between the two stellar
groups with different Fe and s-element content, and this index is not
significantly affected by variations in light elements (such as the O-Na
anticorrelation). The variations in the overall metallicity present in NGC5286
add this object to the class of "anomalous" GCs. Furthermore, the chemical
abundance pattern of NGC5286 resembles that observed in some of the anomalous
GCs, e.g. M22, NGC1851, M2, and the more extreme Omega Centauri, that also show
internal variations in s-elements, and in light elements within stars with
different Fe and s-elements content. In view of the common variations in
s-elements, we propose the term s-Fe-anomalous GCs to describe this sub-class
of objects. The similarities in chemical abundance ratios between these objects
strongly suggest similar formation and evolution histories, possibly associated
with an origin in tidally disrupted dwarf satellites.Comment: 28 pages, 21 figures, accepted for publication in MNRA
The gravitational wave rocket
Einstein's equations admit solutions corresponding to photon rockets. In
these a massive particle recoils because of the anisotropic emission of
photons. In this paper we ask whether rocket motion can be powered only by the
emission of gravitational waves. We use the double series approximation method
and show that this is possible. A loss of mass and gain in momentum arise in
the second approximation because of the emission of quadrupole and octupole
waves.Comment: 10 pages LaTe
Acoustic Phonon-Assisted Resonant Tunneling via Single Impurities
We perform the investigations of the resonant tunneling via impurities
embedded in the AlAs barrier of a single GaAs/AlGaAs heterostructure. In the
characteristics measured at 30mK, the contribution of individual donors
is resolved and the fingerprints of phonon assistance in the tunneling process
are seen. The latter is confirmed by detailed analysis of the tunneling rates
and the modeling of the resonant tunneling contribution to the current.
Moreover, fluctuations of the local structure of the DOS (LDOS) and Fermi edge
singularities are observed.Comment: accepted in Phys. Rev.
A nonstationary generalization of the Kerr congruence
Making use of the Kerr theorem for shear-free null congruences and of
Newman's representation for a virtual charge ``moving'' in complex space-time,
we obtain an axisymmetric time-dependent generalization of the Kerr congruence,
with a singular ring uniformly contracting to a point and expanding then to
infinity. Electromagnetic and complex eikonal field distributions are naturally
associated with the obtained congruence, with electric charge being
necesssarily unit (``elementary''). We conjecture that the corresponding
solution to the Einstein-Maxwell equations could describe the process of
continious transition of the naked ringlike singularitiy into a rotating black
hole and vice versa, under a particular current radius of the singular ring.Comment: 6 pages, twocolum
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