2,344 research outputs found
An Energy-conscious Transport Protocol for Multi-hop Wireless Networks
We present a transport protocol whose goal is to reduce power consumption without compromising delivery requirements of applications. To meet its goal of energy efficiency, our transport protocol (1) contains mechanisms to balance end-to-end vs. local retransmissions; (2) minimizes acknowledgment traffic using receiver regulated rate-based flow control combined with selected acknowledgements and in-network caching of packets; and (3) aggressively seeks to avoid any congestion-based packet loss. Within a recently developed ultra low-power multi-hop wireless network system, extensive simulations and experimental results demonstrate that our transport protocol meets its goal of preserving the energy efficiency of the underlying network.Defense Advanced Research Projects Agency (NBCHC050053
Radion effective theory in the detuned Randall-Sundrum model
We compute the two-derivative low-energy effective action for the radion in
the (supersymmetric) Randall-Sundrum scenario with detuned brane tensions. At
the classical level, a potential automatically stabilizes the distance between
the branes. In the supersymmetric case, supersymmetry can be broken
spontaneously by a vacuum expectation value for the fifth component of the
graviphoton.Comment: 17 pages. JHEP class. New Appendix. Published versio
Cascading DGP
We present a higher codimension generalization of the DGP scenario which,
unlike previous attempts, is free of ghost instabilities. The 4D propagator is
made regular by embedding our visible 3-brane within a 4-brane, each with their
own induced gravity terms, in a flat 6D bulk. The model is ghost-free if the
tension on the 3-brane is larger than a certain critical value, while the
induced metric remains flat. The gravitational force law `cascades' from a 6D
behavior at the largest distances followed by a 5D and finally a 4D regime at
the shortest scales.Comment: 4 pages; one reference added and a typo correcte
Modelling human factors in perceptual multimedia quality: On the role of personality and culture
Perception of multimedia quality is shaped by a rich interplay between system, context, and human factors. While system and context factors are widely researched, few studies in this area consider human factors as sources of systematic variance. This paper presents an analysis on the influence of personality (Five-Factor Model) and cultural traits (Hofstede Model) on the perception of multimedia quality. A set of 144 video sequences (from 12 short movie excerpts) were rated by 114 participants from a cross-cultural population, producing 1232 ratings. On this data, three models are compared: a baseline model that only considers system factors; an extended model that includes personality and culture as human factors; and an optimistic model in which each participant is modeled as a random effect. An analysis shows that personality and cultural traits represent 9.3% of the variance attributable to human factors while human factors overall predict an equal or higher proportion of variance compared to system factors. In addition, the quality-enjoyment correlation varied across the movie excerpts. This suggests that human factors play an important role in perceptual multimedia quality, but further research to explore moderation effects and a broader range of human factors is warranted
Footballs, Conical Singularities and the Liouville Equation
We generalize the football shaped extra dimensions scenario to an arbitrary
number of branes. The problem is related to the solution of the Liouville
equation with singularities and explicit solutions are presented for the case
of three branes. The tensions of the branes do not need to be tuned with each
other but only satisfy mild global constraints.Comment: 15 pages, Refs. added, minor changes. Typo in eq. 4.3 corrected.
Version to be published in PR
The Other Natural Two Higgs Doublet Model
We characterize models where electroweak symmetry breaking is driven by two
light Higgs doublets arising as pseudo-Nambu-Goldstone bosons of new dynamics
above the weak scale. They represent the simplest natural two Higgs doublet
alternative to supersymmetry. We construct their low-energy effective
Lagrangian making only few specific assumptions about the strong sector. These
concern their global symmetries, their patterns of spontaneous breaking and the
sources of explicit breaking. In particular we assume that all the explicit
breaking is associated with the couplings of the strong sector to the Standard
Model fields, that is gauge and (proto)-Yukawa interactions. Under those
assumptions the scalar potential is determined at lowest order by very few free
parameters associated to the top sector. Another crucial property of our
scenarios is the presence of a discrete symmetry, in addition to custodial
SO(4), that controls the -parameter. That can either be simple CP or a
that distinguishes the two Higgs doublets. Among various possibilities we study
in detail models based on SO(6)/SO(4) SO(2), focussing on their
predictions for the structure of the scalar spectrum and the deviations of
their couplings from those of a generic renormalizable two Higgs doublet model.Comment: 54 page
Gaugino mass in AdS space
We study supersymmetric QED in AdS4 with massless matter. At 1-loop the
ultra-violet regulator of the theory generates a contribution to the gaugino
mass that is naively inconsistent with unbroken supersymmetry. We show that
this effect, known in flat space as anomaly mediated supersymmetry breaking, is
required to cancel an infra-red contribution arising from the boundary
conditions in AdS space, which necessarily break chiral symmetry. We also
discuss an analogous UV/IR cancellation that is independent of supersymmetry.Comment: 20 pages, 1 figur
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