1,779 research outputs found
A Photon Peak due to Strong Coupling
We show that if a flavour-less vector meson remains bound after
deconfinement, and if its limiting velocity in the quark-gluon plasma is
subluminal, then this meson produces a distinct peak in the spectrum of thermal
photons emitted by the plasma. We also demonstrate that this effect is a
universal property of all strongly coupled, large-\nc plasmas with a gravity
dual. For the the corresponding peak lies between 3 and 5 GeV and
could be observed at the LHC.Comment: 4 pages, 2 figures - To appear in the conference proceedings for
Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee. V2: minor
correction
Prediction of a Photon Peak in Heavy Ion Collisions
We show that if a flavour-less vector meson remains bound after
deconfinement, and if its limiting velocity in the quark-gluon plasma is
subluminal, then this meson produces a distinct peak in the spectrum of thermal
photons emitted by the plasma. We also demonstrate that this effect is a
universal property of all strongly coupled, large-Nc plasmas with a gravity
dual. For the J/psi the corresponding peak lies between 3 and 5 GeV and could
be observed at LHC.Comment: 4 pages, 5 figures. Minor corrections; references adde
Optical bistability in a fiber ring cavity with synchronous pulsed pump: anomalous and normal dispersion
Passive fiber cavities are basic nonlinear optical systems that are described by simple models - however they have a rich spectrum of complex behaviors (optical bistability, period-doubling bifurcations, chaos, modulational instability). From a practical point of view their study would have direct implications in the understanding of more complex cavity-based optical devices such as fiber lasers, Fabry-Perot lasers or APM lasers. Moreover, passive fiber cavities have potential applications in telecommunications as ultra-short pulse generators and as optical memories using their bistable behavior. This work is a contribution to the study of this bistable behavior with pulsed input, so that the device studied could be used for pulsed optical memory storage.Peer ReviewedPostprint (published version
Holographic heavy ion collisions with baryon charge
We numerically simulate collisions of charged shockwaves in Einstein-Maxwell
theory in anti-de Sitter space as a toy model of heavy ion collisions with
non-zero baryon charge. The stress tensor and the baryon current become well
described by charged hydrodynamics at roughly the same time. The effect of the
charge density on generic observables is typically no larger than 15\%. %The
rapidity profile of the charge is wider than the profile of the local energy
density. We find significant stopping of the baryon charge and compare our
results with those in heavy ion collision experiments.Comment: 18 pages, 10 figure
Longitudinal Coherence in a Holographic Model of p-Pb Collisions
As a model of the longitudinal structure in heavy ion collisions, we simulate
gravitational shock wave collisions in anti-de Sitter space in which each shock
is composed of multiple constituents. We find that all constituents act
coherently, and their separation leaves no imprint on the resulting plasma,
when this separation is , with the
temperature of the plasma at the time when hydrodynamics first becomes
applicable. In particular, the center-of-mass of the plasma coincides with the
center-of-mass of all the constituents participating in the collision, as
opposed to the center-of-mass of the individual collisions. We discuss the
implications for nucleus-nucleus and proton-nucleus collisions.Comment: 5 pages, 3 figures. v2 matches published versio
A New Mechanism of Quark Energy Loss
We show that a heavy quark moving sufficiently fast through a quark-gluon
plasma may lose energy by Cherenkov-radiating mesons. We demonstrate that this
takes place in all strongly coupled, large-Nc plasmas with a gravity dual. The
energy loss is exactly calculable in these models despite being an
O(1/Nc)-effect. We discuss phenomenological implications for heavy-ion
collision experiments.Comment: 4 pages, 4 figures; v2: plot modified, conclusions unchange
Performance analysis of feedback-free collision resolution NDMA protocol
To support communications of a large number of deployed devices while guaranteeing limited signaling load, low energy consumption, and high reliability, future cellular systems require efficient random access protocols. However, how to address the collision resolution at the receiver is still the main bottleneck of these protocols. The network-assisted diversity multiple access (NDMA) protocol solves the issue and attains the highest potential throughput at the cost of keeping devices active to acquire feedback and repeating transmissions until successful decoding. In contrast, another potential approach is the feedback-free NDMA (FF-NDMA) protocol, in which devices do repeat packets in a pre-defined number of consecutive time slots without waiting for feedback associated with repetitions. Here, we investigate the FF-NDMA protocol from a cellular network perspective in order to elucidate under what circumstances this scheme is more energy efficient than NDMA. We characterize analytically the FF-NDMA protocol along with the multipacket reception model and a finite Markov chain. Analytic expressions for throughput, delay, capture probability, energy, and energy efficiency are derived. Then, clues for system design are established according to the different trade-offs studied. Simulation results show that FF-NDMA is more energy efficient than classical NDMA and HARQ-NDMA at low signal-to-noise ratio (SNR) and at medium SNR when the load increases.Peer ReviewedPostprint (published version
Cherenkov mesons as in-medium quark energy loss
We recently showed that a heavy quark moving sufficiently fast through a quark-gluon plasma may lose energy by Cherenkov-radiating mesons [1]. Here we review our previous holographic calculation of the energy loss in N=4 Super Yang-Mills and extend it to longitudinal vector mesons and scalar mesons. We also discuss phenomenological implications for heavy-ion collision experiments. Although the Cherenkov energy loss is an O(1/Nc) effect, a ballpark estimate yields a value of dE/dx for Nc=3 which is comparable to that of other mechanisms
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