4,966 research outputs found
Dynamical phase transitions in one-dimensional hard-particle systems
We analyse a one-dimensional model of hard particles, within ensembles of
trajectories that are conditioned (or biased) to atypical values of the
time-averaged dynamical activity. We analyse two phenomena that are associated
with these large deviations of the activity: phase separation (at low activity)
and the formation of hyperuniform states (at high activity). We consider a
version of the model which operates at constant volume, and a version at
constant pressure. In these non-equilibrium systems, differences arise between
the two ensembles, because of the extra freedom available to the
constant-pressure system, which can change its total density. We discuss the
relationships between different ensembles, mechanical equilibrium, and the
probability cost of rare density fluctuations.Comment: 11 pages, 11 figure
Hyperuniformity and Phase Separation in Biased Ensembles of Trajectories for Diffusive Systems
We analyse biased ensembles of trajectories for diffusive systems. In
trajectories biased either by the total activity or the total current, we use
fluctuating hydrodynamics to show that these systems exhibit phase transtions
into `hyperuniform' states, where large-wavelength density fluctuations are
strongly suppressed. We illustrate this behaviour numerically for a system of
hard particles in one dimension and we discuss how it appears in simple
exclusion processes. We argue that these diffusive systems generically respond
very strongly to any non-zero bias, so that homogeneous states with "normal"
fluctuations (finite compressibility) exist only when the bias is very weak.Comment: 9 pages, 3 figure
A Completely Covariant Approach to Transformation Optics
We show that the Plebanski based approach to transformation optics overlooks
some subtleties in the electrodynamics of moving dielectrics that restricts its
applicability to a certain class of transformations. An alternative, completely
covariant, approach is developed that is more generally applicable and provides
a clearer picture of transformation optics.Comment: 10 pages. This version: Additional references added, corrected a
small error in Eq. (28) (Eq. (29) in present version), some revision of the
text, appendix content moved to the main body of the text, figure removed.
Corresponds more closely to published version. Prepared for a special issue
on transformation optics published by Journal of Optic
General Relativistic Contributions in Transformation Optics
One potentially realistic specification for devices designed with
transformation optics is that they operate with high precision in curved
space-time, such as Earth orbit. This raises the question of what, if any, role
does space-time curvature play in determining transformation media?
Transformation optics has been based on a three-vector representation of
Maxwell's equations in flat Minkowski space-time. I discuss a completely
covariant, manifestly four-dimensional approach that enables transformations in
arbitrary space-times, and demonstrate this approach for stable circular orbits
in the spherically symmetric Schwarzschild geometry. Finally, I estimate the
magnitude of curvature induced contributions to satellite-borne transformation
media in Earth orbit and comment on the level of precision required for
metamaterial fabrication before such contributions become important.Comment: 14 pages, 3 figures. Latest version has expanded analysis,
corresponds to published versio
FIRE Spectroscopy of Five Late-type T Dwarfs Discovered with the Wide-field Infrared Survey Explorer
We present the discovery of five late-type T dwarfs identified with the
Wide-field Infrared Survey Explorer (WISE). Low-resolution near-infrared
spectroscopy obtained with the Magellan Folded-port InfraRed Echellette (FIRE)
reveal strong water and methane absorption in all five sources, and spectral
indices and comparison to spectral templates indicate classifications ranging
from T5.5 to T8.5:. The spectrum of the latest-type source, WISE J1812+2721, is
an excellent match to that of the T8.5 companion brown dwarf Wolf 940B.
WISE-based spectrophotometric distance estimates place these T dwarfs at 12-13
pc from the Sun, assuming they are single. Preliminary fits of the spectral
data to the atmosphere models of Saumon & Marley indicate effective
temperatures ranging from 600 K to 930 K, both cloudy and cloud-free
atmospheres, and a broad range of ages and masses. In particular, two sources
show evidence of both low surface gravity and cloudy atmospheres, tentatively
supporting a trend noted in other young brown dwarfs and exoplanets. In
contrast, the high proper motion T dwarf WISE J2018-7423 exhibits a suppressed
K-band peak and blue spectrophotometric J-K colors indicative of an old,
massive brown dwarf; however, it lacks the broadened Y-band peak seen in
metal-poor counterparts. These results illustrate the broad diversity of
low-temperature brown dwarfs that will be uncovered with WISE.Comment: 19 pages, 13 figures; accepted for publication to Ap
Π‘ΠΎΡΠΈΠ°Π»ΡΠ½Π°Ρ ΠΎΡΠ²Π΅ΡΡΡΠ²Π΅Π½Π½ΠΎΡΡΡ Π±ΠΈΠ·Π½Π΅ΡΠ°: ΠΎΠΏΡΡ Π²Π½Π΅Π΄ΡΠ΅Π½ΠΈΡ, Ρ Π°ΡΠ°ΠΊΡΠ΅ΡΠ½ΡΠ΅ ΡΠ΅ΡΡΡ ΠΈ ΠΎΡΠΎΠ±Π΅Π½Π½ΠΎΡΡΠΈ
Π¦Π΅Π»ΡΡ Π½Π°ΠΏΠΈΡΠ°Π½ΠΈΡ Π΄Π°Π½Π½ΠΎΠΉ ΡΡΠ°ΡΡΠΈ ΡΠ²Π»ΡΠ΅ΡΡΡ ΠΈΠ·ΡΡΠ΅Π½ΠΈΡ ΠΎΠΏΡΡΠ° ΡΠΊΡΠ°ΠΈΠ½ΡΠΊΠΈΡ
ΠΏΡΠ΅Π΄ΠΏΡΠΈΡΡΠΈΠΉ (ΠΊΠΎΠΌΠΏΠ°Π½ΠΈΠΉ) Ρ Π½Π°ΠΈΠ»ΡΡΡΠΈΠΌΠΈ ΠΏΠΎΠΊΠ°Π·Π°ΡΠ΅Π»ΡΠΌΠΈ Π² ΡΡΠ΅ΡΠ΅ ΡΠΎΡΠΈΠ°Π»ΡΠ½ΠΎΠΉ ΠΏΠΎΠ»ΠΈΡΠΈΠΊΠΈ, Π²ΡΡΠ²Π»Π΅Π½ΠΈΠ΅ ΠΈ Π°Π½Π°Π»ΠΈΠ· ΠΎΡΠΎΠ±Π΅Π½Π½ΠΎΡΡΠ΅ΠΉ ΠΈΡ
ΡΠ΅Π°Π»ΠΈΠ·Π°ΡΠΈΠΈ Π΄Π»Ρ ΡΠ°Π·ΡΠ°Π±ΠΎΡΠΊΠΈ ΠΊΠΎΠ½ΡΠ΅ΠΏΡΡΠ°Π»ΡΠ½ΠΎΠ³ΠΎ ΠΏΠΎΠ΄Ρ
ΠΎΠ΄Π° ΠΊ ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΠΌΠΎΠ΄Π΅Π»ΠΈ Π²Π½Π΅Π΄ΡΠ΅Π½ΠΈΡ ΠΏΡΠΈΠ½ΡΠΈΠΏΠΎΠ² ΡΠΎΡΠΈΠ°Π»ΡΠ½ΠΎΠΉ ΠΎΡΠ²Π΅ΡΡΡΠ²Π΅Π½Π½ΠΎΡΡΠΈ Π² Π΄ΡΡΠ³ΠΈΡ
ΠΊΠΎΠΌΠΏΠ°Π½ΠΈΡΡ
(Π½Π° ΠΏΡΠ΅Π΄ΠΏΡΠΈΡΡΠΈΡΡ
).ΠΠ·ΡΡΠ΅Π½ ΠΎΠΏΡΡ Π»ΡΡΡΠΈΡ
ΠΊΠΎΠΌΠΏΠ°Π½ΠΈΠΉ Π£ΠΊΡΠ°ΠΈΠ½Ρ Π² ΡΡΠ΅ΡΠ΅ ΠΊΠΎΡΠΏΠΎΡΠ°ΡΠΈΠ²Π½ΠΎΠΉ ΡΠΎΡΠΈΠ°Π»ΡΠ½ΠΎΠΉ ΠΎΡΠ²Π΅ΡΡΡΠ²Π΅Π½Π½ΠΎΡΡΠΈ; Π²ΡΡΠ²Π»Π΅Π½Ρ Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠ½ΡΠ΅ ΡΠ΅ΡΡΡ ΠΈ ΠΎΡΠΎΠ±Π΅Π½Π½ΠΎΡΡΠΈ ΡΠ°Π·ΡΠ°Π±ΠΎΡΠΊΠΈ ΡΠΎΡΠΈΠ°Π»ΡΠ½ΠΎΠΉ ΠΏΠΎΠ»ΠΈΡΠΈΠΊΠΈ Π² ΠΊΠΎΠΌΠΏΠ°Π½ΠΈΠΈ. ΠΡΠ΅Π΄Π»ΠΎΠΆΠ΅Π½ ΠΊΠΎΠ½ΡΠ΅ΠΏΡΡΠ°Π»ΡΠ½ΡΠΉ ΠΏΠΎΠ΄Ρ
ΠΎΠ΄ ΠΊ ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΠΌΠΎΠ΄Π΅Π»ΠΈ Π²Π½Π΅Π΄ΡΠ΅Π½ΠΈΡ ΠΏΡΠΈΠ½ΡΠΈΠΏΠΎΠ² ΡΠΎΡΠΈΠ°Π»ΡΠ½ΠΎΠΉ ΠΎΡΠ²Π΅ΡΡΡΠ²Π΅Π½Π½ΠΎΡΡΠΈ Π±ΠΈΠ·Π½Π΅ΡΠ°.ΠΠΈΠ²ΡΠ΅Π½ΠΈΠΉ Π΄ΠΎΡΠ²ΡΠ΄ ΠΊΡΠ°ΡΠΈΡ
ΠΊΠΎΠΌΠΏΠ°Π½ΡΠΉ Π£ΠΊΡΠ°ΡΠ½ΠΈ Π² ΡΡΠ΅ΡΡ ΡΠΎΡΡΠ°Π»ΡΠ½ΠΎΡ Π²ΡΠ΄ΠΏΠΎΠ²ΡΠ΄Π°Π»ΡΠ½ΠΎΡΡΡ; Π²ΠΈΡΠ²Π»Π΅Π½Ρ Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠ½Ρ ΡΠΈΡΠΈ ΡΠ° ΠΎΡΠΎΠ±Π»ΠΈΠ²ΠΎΡΡΡ ΡΠΎΠ·ΡΠΎΠ±ΠΊΠΈ ΡΠΎΡΡΠ°Π»ΡΠ½ΠΎΡ ΠΏΠΎΠ»ΡΡΠΈΠΊΠΈ Π² ΠΊΠΎΠΌΠΏΠ°Π½ΡΡ. ΠΠ°ΠΏΡΠΎΠΏΠΎΠ½ΠΎΠ²Π°Π½ΠΈΠΉ ΠΊΠΎΠ½ΡΠ΅ΠΏΡΡΠ°Π»ΡΠ½ΠΈΠΉ ΠΏΡΠ΄Ρ
ΡΠ΄ Π΄ΠΎ ΡΠΎΡΠΌΡΠ²Π°Π½Π½Ρ ΠΌΠΎΠ΄Π΅Π»Ρ Π²ΠΏΡΠΎΠ²Π°Π΄ΠΆΠ΅Π½Π½Ρ ΠΏΡΠΈΠ½ΡΠΈΠΏΡΠ² ΡΠΎΡΡΠ°Π»ΡΠ½ΠΎΡ Π²ΡΠ΄ΠΏΠΎΠ²ΡΠ΄Π°Π»ΡΠ½ΠΎΡΡΡ Π±ΡΠ·Π½Π΅ΡΡ.The experience of the best Ukrainian companies in the sphere of the corporate social responsibility is studied; the personal traits and features of the development of social policy in a company are exposed. The conceptual approach is proposed to the formation of model of business social responsibility principles introduction
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