262 research outputs found
Dark Matter as the signal of Grand Unification
We argue that the existence of Dark Matter (DM) is a possible consequence of
GUT symmetry breaking. In GUTs like SO(10), discrete Z_2 matter parity
(-1)^{3(B-L)} survives despite of broken B-L, and group theory uniquely
determines that the only possible Z_2-odd matter multiplets belong to
representation 16. We construct the minimal non-SUSY SO(10) model containing
one scalar 16 for DM and study its predictions below M_{G}. We find that EWSB
occurs radiatively due to DM couplings to the SM Higgs boson. For thermal relic
DM the mass range M_{DM}\sim (0.1-1) TeV is predicted by model perturbativity
up to M_{G}. For M_{DM}\sim (1) TeV to explain the observed cosmic ray
anomalies with DM decays, there exists a lower bound on the spin-independent
direct detection cross section within the reach of planned experiments.Comment: DM direct detection cross section is corrected by adding s-quark
contribution which turned out to be the dominant one. The prediction is just
below the present CDMS and XENON10 bound. Extended version, RGE-s included,
new references adde
Three-Charge Black Holes on a Circle
We study phases of five-dimensional three-charge black holes with a circle in
their transverse space. In particular, when the black hole is localized on the
circle we compute the corrections to the metric and corresponding
thermodynamics in the limit of small mass. When taking the near-extremal limit,
this gives the corrections to the constant entropy of the extremal three-charge
black hole as a function of the energy above extremality. For the partial
extremal limit with two charges sent to infinity and one finite we show that
the first correction to the entropy is in agreement with the microscopic
entropy by taking into account that the number of branes shift as a consequence
of the interactions across the transverse circle. Beyond these analytical
results, we also numerically obtain the entire phase of non- and near-extremal
three- and two-charge black holes localized on a circle. More generally, we
find in this paper a rich phase structure, including a new phase of
three-charge black holes that are non-uniformly distributed on the circle. All
these three-charge black hole phases are found via a map that relates them to
the phases of five-dimensional neutral Kaluza-Klein black holes.Comment: 58 pages, 10 figures; v2: Corrected typos, version appearing in JHE
Memory maps : Reading RRAM devices without power consumption
Producción CientíficaA comparative study of MIM-RRAM structures with different insulator materials is presented. Admittance memory mapping was carried out at 0 V dc bias, revealing two clearly separated states, both in terms of conductance and susceptance. The memory in the ON state can be modeled by means of a two parameter (resistance and inductance) equivalent circuit. The parameter extraction provides memory maps for the resistance and the inductance as well. The transition shapes between the ON and OFF state are different for each structure due to specific physical mechanisms.Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (grant TEC2014-52152-C3-3-R)Fondo Europeo de Desarrollo Regional (project TK134)Estonian Research Agency (grants IUT2-24 and PRG4
Strength of Correlations in electron and hole doped cuprates
High temperature superconductivity was achieved by introducing holes in a
parent compound consisting of copper oxide layers separated by spacer layers.
It is possible to dope some of the parent compounds with electrons, and their
physical properties are bearing some similarities but also significant
differences from the hole doped counterparts. Here, we use a recently developed
first principles method, to study the electron doped cuprates and elucidate the
deep physical reasons why their behavior is so different than the hole doped
materials. We find that electron doped compounds are Slater insulators, e.g. a
material where the insulating behavior is the result of the presence of
magnetic long range order. This is in sharp contrast with the hole doped
materials, where the parent compound is a Mott charge transfer insulator,
namely a material which is insulating due to the strong electronic correlations
but not due to the magnetic order.Comment: submitted to Nature Physic
Implications of the 125 GeV Higgs boson for scalar dark matter and for the CMSSM phenomenology
We study phenomenological implications of the ATLAS and CMS hint of a GeV Higgs boson for the singlet, and singlet plus doublet non-supersymmetric
dark matter models, and for the phenomenology of the CMSSM. We show that in
scalar dark matter models the vacuum stability bound on Higgs boson mass is
lower than in the standard model and the 125 GeV Higgs boson is consistent with
the models being valid up the GUT or Planck scale. We perform a detailed study
of the full CMSSM parameter space keeping the Higgs boson mass fixed to GeV, and study in detail the freeze-out processes that imply the observed
amount of dark matter. After imposing all phenomenological constraints except
for the muon we show that the CMSSM parameter space is divided
into well separated regions with distinctive but in general heavy sparticle
mass spectra. Imposing the constraint introduces severe tension
between the high SUSY scale and the experimental measurements -- only the
slepton co-annihilation region survives with potentially testable sparticle
masses at the LHC. In the latter case the spin-independent DM-nucleon
scattering cross section is predicted to be below detectable limit at the
XENON100 but might be of measurable magnitude in the general case of light dark
matter with large bino-higgsino mixing and unobservably large scalar masses.Comment: 17 pages, 7 figures. v3: same as published versio
New Solution for Neutrino Masses and Leptogenesis in Adjoint SU(5)
We investigate baryogenesis via leptogenesis and generation of neutrino
masses and mixings through the Type I plus Type III seesaw plus an one-loop
mechanism in the context of Renormalizable Adjoint SU(5) theory. One light
neutrino remains massless, because the contributions of three heavy Majorana
fermions \rho_0, \rho_3 and \rho_8 to the neutrino mass matrix are not linearly
independent. However none of these heavy fermions is decoupled from the
generation of neutrino masses. This opens a new range in parameter space for
successful leptogenesis, in particular, allows for inverted hierarchy of the
neutrino masses.Comment: 16 pages, 4 figures; references added and typos fixe
Nucleon-Gold Collisions at 200 AGeV Using Tagged d+Au Interactions in PHOBOS
Forward calorimetry in the PHOBOS detector has been used to study charged
hadron production in d+Au, p+Au and n+Au collisions at sqrt(s_nn) = 200 GeV.
The forward proton calorimeter detectors are described and a procedure for
determining collision centrality with these detectors is detailed. The
deposition of energy by deuteron spectator nucleons in the forward calorimeters
is used to identify p+Au and n+Au collisions in the data. A weighted
combination of the yield of p+Au and n+Au is constructed to build a reference
for Au+Au collisions that better matches the isospin composition of the gold
nucleus. The p_T and centrality dependence of the yield of this improved
reference system is found to match that of d+Au. The shape of the charged
particle transverse momentum distribution is observed to extrapolate smoothly
from pbar+p to central d+Au as a function of the charged particle
pseudorapidity density. The asymmetry of positively- and negatively-charged
hadron production in p+Au is compared to that of n+Au. No significant asymmetry
is observed at mid-rapidity. These studies augment recent results from
experiments at the LHC and RHIC facilities to give a more complete description
of particle production in p+A and d+A collisions, essential for the
understanding the medium produced in high energy nucleus-nucleus collisions.Comment: 17 pages, 18 figure
Magnetic Heisenberg-chain/pp-wave correspondence
We find a decoupling limit of planar N=4 super Yang-Mills (SYM) on R x S^3 in
which it becomes equivalent to the ferromagnetic XXX_{1/2} Heisenberg spin
chain in an external magnetic field. The decoupling limit generalizes the one
found in hep-th/0605234 corresponding to the case with zero magnetic field. The
presence of the magnetic field is seen to break the degeneracy of the vacuum
sector and it has a non-trivial effect on the low energy spectrum. We find a
general connection between the Hagedorn temperature of planar N=4 SYM on R x
S^3 in the decoupling limit and the thermodynamics of the Heisenberg chain.
This is used to study the Hagedorn temperature for small and large value of the
effective coupling. We consider the dual decoupling limit of type IIB strings
on AdS_5 x S^5. We find a Penrose limit compatible with the decoupling limit
that gives a magnetic pp-wave background. The breaking of the symmetry by the
magnetic field on the gauge theory side is seen to have a geometric counterpart
in the derivation of the Penrose limit. We take the decoupling limit of the
pp-wave spectrum and succesfully match the resulting spectrum to the low energy
spectrum on the gauge theory side. This enables us to match the Hagedorn
temperature of the pp-wave to the Hagedorn temperature of the gauge theory for
large effective coupling. This generalizes the results of hep-th/0608115 to the
case of non-zero magnetic field.Comment: 35 pages, 2 figures. v2: Refs. adde
The sequences of 150,119 genomes in the UK Biobank
Detailed knowledge of how diversity in the sequence of the human genome affects phenotypic diversity depends on a comprehensive and reliable characterization of both sequences and phenotypic variation. Over the past decade, insights into this relationship have been obtained from whole-exome sequencing or whole-genome sequencing of large cohorts with rich phenotypic data(1,2). Here we describe the analysis of whole-genome sequencing of 150,119 individuals from the UK Biobank(3). This constitutes a set of high-quality variants, including 585,040,410 single-nucleotide polymorphisms, representing 7.0% of all possible human single-nucleotide polymorphisms, and 58,707,036 indels. This large set of variants allows us to characterize selection based on sequence variation within a population through a depletion rank score of windows along the genome. Depletion rank analysis shows that coding exons represent a small fraction of regions in the genome subject to strong sequence conservation. We define three cohorts within the UK Biobank: a large British Irish cohort, a smaller African cohort and a South Asian cohort. A haplotype reference panel is provided that allows reliable imputation of most variants carried by three or more sequenced individuals. We identified 895,055 structural variants and 2,536,688 microsatellites, groups of variants typically excluded from large-scale whole-genome sequencing studies. Using this formidable new resource, we provide several examples of trait associations for rare variants with large effects not found previously through studies based on whole-exome sequencing and/or imputation
Innovative in vitro method to study ventilator induced lung injury.
To access publisher's full text version of this article, please click on the hyperlink in Additional Links field or click on the hyperlink at the top of the page marked DownloadMechanical ventilation (MV) is a life-saving therapy for critically ill patients, alleviating the work of breathing and supporting adequate gas exchange. However, MV can cause ventilator induced lung injury (VILI) by baro/volu- and atelectrauma, even lead to acute respiratory distress syndrome (ARDS), and substantially augment mortality. There is a need for specific biomarkers and novel research platforms for VILI/ARDS research to study these detrimental disorders and seek ways to avoid or prevent them. Previous in vitro studies on bronchial epithelium, cultured in air-liquid interface (ALI) conditions, have generally utilized static or constant pressure. We have developed a Cyclical Pressure ALI Device (CPAD) that enables cyclical stress on ALI cultured human bronchial cells, with the aim of mimicking the effects of MV. Using CPAD we were able to analyze differentially expressed VILI/ARDS and innate immunity associated genes along with increased expression of associated proteins. CPAD provides an easy and accessible way to analyze functional and phenotypic changes that occur during VILI and may provide a platform for future drug testing.Technology development fund - Icelandic research council
University of Iceland
Land-spitali, University Hospital, Science fun
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