2,063 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
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
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
Supersymmetry phenomenology beyond the MSSM after 5/fb of LHC data
We briefly review the status of motivated beyond-the-MSSM phenomenology in
the light of the LHC searches to date. In particular, we discuss the conceptual
consequences of the exclusion bounds, of the hint for a Higgs boson at about
125 GeV, and of interpreting the excess of direct CP violation in the charm
sector as a signal of New Physics. We try to go into the various topics in a
compact way while providing a relatively rich list of references, with
particular attention to the most recent developments.Comment: 20 pages + refs. v2: minor modifications, published versio
Axion-Higgs Unification
In theories with no fundamental scalars, one gauge group can become strong at
a large scale Lambda and spontaneously break a global symmetry, producing the
Higgs and the axion as composite pseudo-Nambu-Goldstone bosons. We show how
KSVZ and DFSZ axion models can be naturally realised. The assumption Lambda
around 10^{11} GeV is phenomenologically favoured because: a) The axion solves
the QCD theta problem and provides the observed DM abundance; b) The observed
Higgs mass is generated via RGE effects from a small Higgs quartic coupling at
the compositeness scale, provided that the Higgs mass term is fine-tuned to be
of electroweak size; c) Lepton, quark as well as neutrino masses can be
obtained from four-fermion operators at the compositeness scale. d) The extra
fermions can unify the gauge couplings.Comment: 19 pages. Refs. added and eq. 3.6 fixe
Auswirkungen von depressiven Störungen auf die kognitive Leistungsfähigkeit und die Fahrkompetenz
Depressive Störungen können neben den Erstrangsymptomen „depressive Stimmung“, „Verlust von Interesse oder Freude“ und „erhöhte Ermüdbarkeit“ mit einer großen Anzahl an weiteren Symptomen einhergehen. Folgende kognitive Defizite sind kennzeichnend: Störungen der kognitiven Flexibilität, des Arbeitsgedächtnisses, des freien Abrufs von Gedächtnisinhalten, der geteilten Aufmerksamkeit und von Teilbereichen der selektiven Aufmerksamkeit.
Die Bundesanstalt für Straßenwesen (BASt) und wissenschaftliche Forschungsarbeiten konnten eine Reihe an Leistungs- und Persönlichkeitsmaßen identifizieren, welche eine ausreichende psychische Leistungsfähigkeit im Straßenverkehr gewährleisten sollen. Obwohl sich die hierbei hervorgehobenen kognitiven Leistungsfunktionen nahezu umfassend mit den Defizitbereichen bei depressiven Störungen überschneiden und bisher kein rein linearer Zusammenhang zwischen der Schwere der depressiven Symptomatik und dem Ausprägungsgrad kognitiver Beeinträchtigungen gefunden werden konnte, besagt die aktuelle Rechtslage, dass lediglich bei schweren depressiven Episoden die Fahreignung anzuzweifeln sei.
Ziele der vorliegenden Arbeit: Zum einen sollte überprüft werden, ob sich die in der Literatur berichteten Unterschiede zwischen depressiven Patienten und gesunden Vergleichspersonen in der kognitiven Leistungsfähigkeit, bei der Fahrkompetenz, bei der Selbstbeschreibung und im Risikoverhalten finden lassen. Zum anderen wurde zu bestimmen versucht, welche dieser Maße hauptverantwortlich für Unterschiede in der Fahrkompetenz sind.
Methode: Hierzu bearbeitete eine Gruppe stationär-psychiatrischer Patienten mit unipolarer Depression jeweils unmittelbar nach stationärer Aufnahme und bei Entlassung (neuro-) psychologische Testverfahren. Darüber hinaus wurde zeitnah zu den Testungen eine praktische Fahrerprobung in einem Fahrschulauto durchgeführt. Ein dritter Schwerpunkt der vorliegenden Arbeit bestand darin, die wissenschaftliche Güte dieser praktischen Fahrverhaltensprobe zu überprüfen. Alle Untersuchungen wurden parallel auch mit einer Kontrollgruppe körperlich und psychisch gesunder Probanden durchgeführt.
Ergebnisse: Die Fahrverhaltensprobe konnte strenge wissenschaftliche und verkehrspsychologische Anforderungen erfüllen. Es zeigte sich, dass sich die Patienten neben dem Ausmaß ihrer subjektiven und objektiven Depressivität, auch in einer Reihe von Leistungs- und Persönlichkeitsmaßen von den Kontrollpersonen unterschieden. Es ließen sich sowohl einzelne wie auch Kombinationen an Variablen identifizieren, die bereits für die eher geringe Stichprobengröße der Studie die Fahrkompetenz der Probanden mit einem zufrieden stellenden Maß an Sensitivität und Spezifität vorhersagten.
Diskussion: Mit dieser Arbeit wurde erstmals bei Patienten mit mittelschwerer Depression sowohl anhand neuropsychologischer Testverfahren als auch mit Hilfe einer praktischen Fahrverhaltensprobe untersucht, welche Auswirkungen deren Erkrankung auf die Fahrkompetenz hat. Vorangegangene Studien konnten aber bereits die Annahme der BASt, dass nur bei schweren depressiven Episoden die Fahreignung fraglich sei, deutlich in Frage stellen. Die vorliegende Studie stützt die bisherigen Erkenntnisse und zeigt zusätzlich auf, dass auch bei einer praktischen Fahrverhaltensprobe, die den Anforderungen der BASt entspricht, nicht von vergleichbaren Leistungen bei depressiven Patienten und gesunden Kontrollen auszugehen ist. Die geringe Stichprobengröße lässt allerdings eine Generalisierung der Ergebnisse nicht zu. Weitere Forschungsarbeit in dieser Richtung ist erforderlich
Spin and a Running Radius in RS1
We develop a renormalization group formalism for the compactified
Randall-Sundrum scenario wherein the extra-dimensional radius serves as the
scaling parameter. Couplings on the hidden brane scale as we move within local
effective field theories with varying size of the warped extra dimension. We
consider this RG approach applied to U(1) gauge theories and gravity. We use
this method to derive a low energy effective theory.Comment: 18 pages, minor changes, references adde
Bounding wide composite vector resonances at the LHC
In composite Higgs models (CHMs), electroweak precision data generically push
colourless composite vector resonances to a regime where they dominantly decay
into pairs of light top partners. This greatly attenuates their traces in
canonical collider searches, tailored for narrow resonances promptly decaying
into Standard Model final states. By reinterpreting the CMS same-sign dilepton
(SS2) analysis at the Large Hadron Collider (LHC), originally designed to
search for top partners with electric charge , we demonstrate its
significant coverage over this kinematical regime. We also show the reach of
the 13 TeV run of the LHC, with various integrated luminosity options, for a
possible upgrade of the SS2 search. The top sector of CHMs is found to be
more fine-tuned in the presence of colourless composite resonances in the few
TeV range.Comment: 9 pages, 5 figures. Minor corrections for publication in JHE
Discovering the composite Higgs through the decay of a heavy fermion
A possible composite nature of the Higgs could be revealed at the early stage
of the LHC, by analyzing the channels where the Higgs is produced from the
decay of a heavy fermion. The Higgs production from a singly-produced heavy
bottom, in particular, proves to be a promising channel. For a value \lambda=3
of the Higgs coupling to a heavy bottom, for example, we find that, considering
a 125 GeV Higgs which decays into a pair of b-quarks, a discovery is possible
at the 8 TeV LHC with 30 fb^{-1} if the heavy bottom is lighter than roughly
530 GeV (while an observation is possible for heavy bottom masses up to 650
GeV). Such a relatively light heavy bottom is realistic in composite Higgs
models of the type considered and, up to now, experimentally allowed. At
\sqrt{s}=14 TeV the LHC sensitivity on the channel increases significantly.
With \lambda=3 a discovery can occur, with 100 fb^{-1}, for heavy bottom masses
up to 1040 GeV. In the case the heavy bottom was as light as 500 GeV, the 14
TeV LHC would be sensitive to the measure of the \lambda\ coupling in basically
the full range \lambda>1 predicted by the theory.Comment: 25 pp. v2: Minor changes. v3: Version accepted for publication in
JHEP. v4: typos fixe
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