We evaluate the exposure during nadir observations with JEM-EUSO, the Extreme Universe Space Obser-\ud
vatory, on-board the Japanese Experiment Module of the International Space Station. Designed as a mis-\ud
sion to explore the extreme energy Universe from space, JEM-EUSO will monitor the Earth’s nighttime\ud
atmosphere to record the ultraviolet light from tracks generated by extensive air showers initiated by\ud
ultra-high energy cosmic rays. In the present work, we discuss the particularities of space-based obser-\ud
vation and we compute the annual exposure in nadir observation. The results are based on studies of the\ud
expected trigger aperture and observational duty cycle, as well as, on the investigations of the effects of\ud
clouds and different types of background light. We show that the annual exposure is about one order of\ud
magnitude higher than those of the presently operating ground-based observatories
We study the phase ordering of parametrically and incoherently driven microcavity polaritons after an infinitely rapid quench across the critical region. We confirm that the system, despite its driven-dissipative nature, satisfies the dynamical scaling hypothesis for both driving schemes by exhibiting self-similar patterns for the two-point correlator at late times of the phase ordering. We show that polaritons are characterized by the dynamical critical exponent z≈2 with topological defects playing a fundamental role in the dynamics, giving logarithmic corrections both to the power-law decay of the number of vortices and to the associated growth of the characteristic length scale.
Driven-dissipative systems in two dimensions can differ substantially from their equilibrium counterparts. In particular, a dramatic loss of off-diagonal algebraic order and superfluidity has been predicted to occur because of the interplay between coherent dynamics and external drive and dissipation in the thermodynamic limit. We show here that the order adopted by the system can be substantially altered by a simple, experimentally viable tuning of the driving process. More precisely, by considering the longwavelength phase dynamics of a polariton quantum fluid in the optical parametric oscillator regime, we demonstrate that simply changing the strength of the pumping mechanism in an appropriate parameter range can substantially alter the level of effective spatial anisotropy induced by the driving laser and move the system into distinct scaling regimes. These include (i) the classic algebraically ordered superfluid below the Berezinskii-Kosterlitz-Thouless (BKT) transition, as in equilibrium; (ii) the nonequilibrium, longwavelength-fluctuation-dominated Kardar-Parisi-Zhang (KPZ) phase; and the two associated topologicaldefect-dominated disordered phases caused by proliferation of (iii) entropic BKT vortex-antivortex pairs or (iv) repelling vortices in the KPZ phase. Furthermore, by analyzing the renormalization group flow in a finite system, we examine the length scales associated with these phases and assess their observability in current experimental conditions.
We show that the two-time physics model leads to a mechanical system with
Dirac brackets consistent with the Snyder noncommutative space. An Euclidean
version of this space is also obtained and it is shown that both spaces have a
dual system describing a particle in a curved space-time.Comment: 5 pages, RevTeX4. References adde
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