13,741 research outputs found
Noncentrosymmetric plasmon modes and giant terahertz photocurrent in a two-dimensional plasmonic crystal
We introduce and theoretically study the plasmon-photogalvanic effect in the
planar noncentrosymmetric plasmonic crystal containing a homogeneous
two-dimensional electron system gated by a periodic metal grating with an
asymmetric unit cell. The plasmon-photogalvanic DC current arises due to the
two-dimensional electron drag by the noncentrosymmetric plasmon modes excited
under normal incidence of terahertz radiation. We show that the collective
plasmon modes of the planar plasmonic crystal become strongly
noncentrosymmetric in the weak coupling regime of their anticrossing. Large
plasmon wavevector (which is typically by two-three orders of magnitude greater
than the terahertz photon wavevector) along with strong near-field enhancement
at the plasmon resonance make the plasmonic drag a much stronger effect
compared to the photon drag observed in conventional two-dimensional electron
systems.Comment: 9 pages, 10 figures, submitted to Physical Review
Hygienic requirements of urban living environment in the Russian Federation and in Italy: a comparison
Introduzione/scopo. La pianificazione urbana tende a contenere e regolamentare la crescita urbana consentendo uno sviluppo sostenibile a livello ambientale, sociale e sanitario. Nel presente lavoro gli autori hanno confrontato i quadri normativi della Federazione Russ e dell’Italia ponendo particolare attenzione agli aspetti urbani degli spazi abitativi.
Metodo. Considerando la ponderosa produzione normativa nei due paesi, il lavoro ha preso in esame le normative a livello nazionale per l’Italia e federale per la Russia, tenendo principalmente conto dei seguenti aspetti: strumenti di pianificazione urbana e protezione ambientale e sanitaria degli spazi abitativi.
Risultati. I problemi relativi alla sicurezza igienico-sanitaria dell’ambiente di vita in Russia sono essenzialmente riconducibili a due sistemi normativi (SNiP e
SanPiN), mentre in Italia rientrano nel D.M. 05/07/1975. I principi fondamentali della pianificazione urbana in Russia sono dettati da una norma federale, mentre in
Italia sono recepiti nel Piano Regolatore Generale (PRG) comunale e nei diversi regolamenti locali, dove si riasriassume tutta la normativa sovraordinata. Gli aspetti legati alla qualità ambientale, infine, in entrambi i paesi sono disciplinati da varie leggi specifiche (federali e statali); un articolato sistema di norme che tengono conto dei
potenziali impatti sulla salute e sull’ambiente
Conclusioni. Gli autori ritengono che dovrebbero essere sviluppati, specialmente in Italia che si trova nettamente più indietro da questo punto di vista, strumenti normativi chiari e aggiornati aventi per oggetto l’igiene degli edifici e degli ambienti urbani, basati sulle più recenti acquisizioni di letteratura scientifica internazionale nell’intento di garantire i più alti standard in materia di tutela della Salute Pubblica.Aim. Urban planning tries to contain and regulate the uncontrolled growth of cities, encouraging their sustainable development at environmental, social and health levels. In the present work, the authors compare the regulatory frameworks of the Russian Federation and of Italy, with particular attention paid to the urban aspects of living spaces.
Method. Considering the extant normative production in the two countries, the authors examine national legislation for Italy and federal legislation for Russia, mainly taking into account the following aspects: urban planning tools and environmental and sanitary protection of living spaces.
Results. Hygienic-sanitary requirements regarding living environment in Russia are essentially expressed by two regulatory systems (SNiP and SanPiN), while in Italy they are regulated by the D.M. 07/05/1975. The main principles of urban planning in Russia are expressed by federal standards, while in Italy they are incorporated in the Municipal General Plan (PRG) and in the various local regulations, where all the superordinate regulations are summarized. Finally, aspects related to environmental quality in both countries are governed by various specific laws (federal and state); a complex system of rules that take into account potential impacts on health and the environment.
Conclusions. The authors reckon that clear and updated regulatory tools should be developed, especially in Italy that lags behind, regarding the building and urban hygiene, relying on the most recent acquisitions of international scientific literature in order to guarantee the highest standards in Public Health safeguard
Affine Toric SL(2)-embeddings
In 1973 V.L.Popov classified affine SL(2)-embeddings. He proved that a
locally transitive SL(2)-action on a normal affine three-dimensional variety X
is uniquely determined by a pair (p/q, r), where 0<p/q<=1 is an uncancelled
fraction and r is a positive integer. Here r is the order of the stabilizer of
a generic point. In this paper we show that the variety X is toric, i.e. admits
a locally transitive action of an algebraic torus, if and only if r is
divisible by q-p. To do this we prove the following necessary and sufficient
condition for an affine G/H-embedding to be toric. Suppose X is a normal affine
variety, G is a simply connected semisimple algebraic group acting regularly on
X, H is a closed subgroup of G such that the character group
is finite and G/H -> X is a dense open equivariant embedding. Then X is toric
if and only if there exist a quasitorus T and a -module V such
that . The key role in the proof plays D. Cox's
construction.Comment: 16 page
Band-aid for information loss from black holes
We summarize, simplify and extend recent work showing that small deviations
from exact thermality in Hawking radiation, first uncovered by Kraus and
Wilczek, have the capacity to carry off the maximum information content of a
black hole. This goes a considerable way toward resolving a long-standing
"information-loss paradox"
The ontology of temperature in nonequilibrium systems
The laws of thermodynamics provide a clear concept of the temperature for an
equilibrium system in the continuum limit. Meanwhile, the equipartition theorem
allows one to make a connection between the ensemble average of the kinetic
energy and the uniform temperature. When a system or its environment is far
from equilibrium, however, such an association does not necessarily apply. In
small systems, the regression hypothesis may not even apply. Herein, we show
that in small nonequilibrium systems, the regression hypothesis still holds
though with a generalized definition of the temperature. The latter must now be
defined for each such manifestation.Comment: J.Chem.Phys. (in press); 23 pages, 3 figures, 1 tabl
Dressing Symmetries of Holomorphic BF Theories
We consider holomorphic BF theories, their solutions and symmetries. The
equivalence of Cech and Dolbeault descriptions of holomorphic bundles is used
to develop a method for calculating hidden (nonlocal) symmetries of holomorphic
BF theories. A special cohomological symmetry group and its action on the
solution space are described.Comment: 14 pages, LaTeX2
Critical velocity of a mobile impurity in one-dimensional quantum liquids
We study the notion of superfluid critical velocity in one spatial dimension.
It is shown that for heavy impurities with mass exceeding a critical mass
, the dispersion develops periodic metastable branches resulting
in dramatic changes of dynamics in the presence of an external driving force.
In contrast to smooth Bloch Oscillations for , a heavy impurity
climbs metastable branches until it reaches a branch termination point or
undergoes a random tunneling event, both leading to an abrupt change in
velocity and an energy loss. This is predicted to lead to a non-analytic
dependence of the impurity drift velocity on small forces.Comment: 5 pages, 2 figures; New version with Supplemental Material (3 pages,
6 figures); Accepted to PR
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Stochastic modelling of the effects of interdependencies between critical infrastructure
An approach to Quantitative Interdependency Analysis, in the context of Large Complex Critical Infrastructures, is presented in this paper. A Discrete state–space, Continuous–time, Stochastic Process models the operation of critical infrastructure, taking interdependencies into account. Of primary interest are the implications of both model detail (that is, level of model abstraction) and model parameterisation for the study of dependencies. Both of these factors are observed to affect the distribution of cascade–sizes within and across infrastructure
Statistical properties of Klauder-Perelomov coherent states for the Morse potential
We present in this paper a realistic construction of the coherent states for
the Morse potential using the Klauder-Perelomov approach . We discuss the
statistical properties of these states, by deducing the Q- and P-distribution
functions. The thermal expectations for the quantum canonical ideal gas of the
Morse oscillators are also calculated
Quantum-corrected ultraextremal horizons and validity of WKB in massless limit
We consider quantum backreaction of the quantized scalar field with an
arbitrary mass and curvature coupling on ultraextremal horizons. The problem is
distinguished in that (in contrast to non-extremal or extremal black holes) the
WKB approximation remains valid near (which is the radius of the
horizon) even in the massless limit. We examine the behavior of the
stress-energy tensor of the quantized field near and show that
quantum-corrected objects under discussion do exist. In the limit of the large
mass our results agree with previous ones known in literature.Comment: revtex4, 9 page
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