373 research outputs found
A second look at N=1 supersymmetric AdS_4 vacua of type IIA supergravity
We show that a class of type IIA vacua recently found within the N=4
effective approach corresponds to compactification on Ads_4 \times S^3 \times
S^3/Z_2^3. The results obtained using the effective method completely match the
general ten-dimensional analysis for the existence of N=1 warped
compactifications on Ads_4 \times M_6. In particular, we verify that the
internal metric is nearly-Kahler and that for specific values of the parameters
the Bianchi identity of the RR 2-form is fulfilled without sources. For another
range of parameters, including the massless case, the Bianchi identity is
satisfied when D6-branes are introduced. Solving the tadpole cancellation
conditions in D=4 we are able to find examples of appropriate sets of branes.
In the second part of this paper we describe how an example with internal space
CP^3 but with non nearly-Kahler metric fits into the general analysis of flux
vacua.Comment: Latex file, 35 pages, no figures. Reference added, minor corrections
adde
Coordination of Dynamic Software Components with JavaBIP
JavaBIP allows the coordination of software components by clearly separating
the functional and coordination aspects of the system behavior. JavaBIP
implements the principles of the BIP component framework rooted in rigorous
operational semantics. Recent work both on BIP and JavaBIP allows the
coordination of static components defined prior to system deployment, i.e., the
architecture of the coordinated system is fixed in terms of its component
instances. Nevertheless, modern systems, often make use of components that can
register and deregister dynamically during system execution. In this paper, we
present an extension of JavaBIP that can handle this type of dynamicity. We use
first-order interaction logic to define synchronization constraints based on
component types. Additionally, we use directed graphs with edge coloring to
model dependencies among components that determine the validity of an online
system. We present the software architecture of our implementation, provide and
discuss performance evaluation results.Comment: Technical report that accompanies the paper accepted at the 14th
International Conference on Formal Aspects of Component Softwar
Clinically significant anxiety as a risk factor for dementia in the elderly community
Objective: To evaluate whether clinically significant anxiety is an independent risk factor for dementia, taking into account both depression among potentially confounding factors and the competing risk of death.
Method: During the Zaragoza Dementia and Depression (ZARADEMP) study, a random sample of community dwellers aged 55 years or older was assessed (n = 4803), and a two-wave, 4.5-year follow-up was completed. Geriatric Mental State (GMS)-AGECAT criteria were used to diagnose anxiety and DSM-IV criteria were applied to diagnose incident dementia. The multivariate Fine and Gray regression model was implemented to calculate dementia risk.
Results: Compared with non-cases (GMS-AGECAT criteria), the incidence rate of dementia was significantly higher in subcases of anxiety, and particularly significant in the cases of anxiety (incidence rate ratio (IRR): 2.77; PÂ =Â 0.010). Cases of anxiety, but not subcases, at baseline were significantly associated with dementia risk (adjusted subdistribution hazard ratio (SHR): 2.7; PÂ =Â 0.019).
Conclusion: Clinically significant anxiety is associated with an almost threefold increase in the risk of dementia in the population, even when controlling for depression and considering mortality in the competing risks model
Open string wavefunctions in flux compactifications
We consider compactifications of type I supergravity on manifolds with SU(3)
structure, in the presence of RR fluxes and magnetized D9-branes, and analyze
the generalized Dirac and Laplace-Beltrami operators associated to the D9-brane
worldvolume fields. These compactifications are T-dual to standard type IIB
toroidal orientifolds with NSNS and RR 3-form fluxes and D3/D7 branes. By using
techniques of representation theory and harmonic analysis, the spectrum of open
string wavefunctions can be computed for Lie groups and their quotients, as we
illustrate with explicit twisted tori examples. We find a correspondence
between irreducible unitary representations of the Kaloper-Myers algebra and
families of Kaluza-Klein excitations. We perform the computation of 2- and
3-point couplings for matter fields in the above flux compactifications, and
compare our results with those of 4d effective supergravity.Comment: 89 pages, 4 figures. v3: more typos corrected, version published in
JHE
D-branes on AdS flux compactifications
We study D-branes in N=1 flux compactifications to AdS_4. We derive their
supersymmetry conditions and express them in terms of background generalized
calibrations. Basically because AdS has a boundary, the analysis of stability
is more subtle and qualitatively different from the usual case of Minkowski
compactifications. For instance, stable D-branes filling AdS_4 may wrap trivial
internal cycles. Our analysis gives a geometric realization of the
four-dimensional field theory approach of Freedman and collaborators.
Furthermore, the one-to-one correspondence between the supersymmetry conditions
of the background and the existence of generalized calibrations for D-branes is
clarified and extended to any supersymmetric flux background that admits a
time-like Killing vector and for which all fields are time-independent with
respect to the associated time. As explicit examples, we discuss supersymmetric
D-branes on IIA nearly Kaehler AdS_4 flux compactifications.Comment: 43 pages, 2 pictures, 1 table; v2: added references, color to figure
and corrected typo in (6.21b
DWSB in heterotic flux compactifications
We address the construction of non-supersymmetric vacua in heterotic
compactifications with intrinsic torsion and background fluxes. In particular,
we implement the approach of domain-wall supersymmetry breaking (DWSB)
previously developed in the context of type II flux compactifications. This
approach is based on considering backgrounds where probe NS5-branes wrapping
internal three-cycles and showing up as four-dimensional domain-walls do not
develop a BPS bound, while all the other BPS bounds characterizing the N=1
supersymmetric compactifications are preserved at tree-level. Via a scalar
potential analysis we provide the conditions for these backgrounds to solve the
ten-dimensional equations of motion including order \alpha' corrections. We
also consider backgrounds where some of the NS5-domain-walls develop a BPS
bound, show their relation to no-scale SUSY-breaking vacua and construct
explicit examples via elliptic fibrations. Finally, we consider backgrounds
with a non-trivial gaugino condensate and discuss their relation to
supersymmetric and non-supersymmetric vacua in the present context.Comment: 56 pages, 1 figur
U-dual fluxes and Generalized Geometry
We perform a systematic analysis of generic string flux compactifications,
making use of Exceptional Generalized Geometry (EGG) as an organizing
principle. In particular, we establish the precise map between fluxes, gaugings
of maximal 4d supergravity and EGG, identifying the complete set of gaugings
that admit an uplift to 10d heterotic or type IIB supegravity backgrounds. Our
results reveal a rich structure, involving new deformations of 10d supergravity
backgrounds, such as the RR counterparts of the -deformation. These new
deformations are expected to provide the natural extension of the
-deformation to full-fledged F-theory backgrounds. Our analysis also
provides some clues on the 10d origin of some of the particularly less
understood gaugings of 4d supergravity. Finally, we derive the explicit
expression for the effective superpotential in arbitrary N = 1 heterotic or
type IIB orientifold compactifications, for all the allowed fluxes.Comment: 58 pages, 6 table
Large-Volume Flux Compactifications: Moduli Spectrum and D3/D7 Soft Supersymmetry Breaking
We present an explicit calculation of the spectrum of a general class of
string models, corresponding to Calabi-Yau flux compactifications with
h_{1,2}>h_{1,1}>1 with leading perturbative and non-perturbative corrections,
in which all geometric moduli are stabilised as in hep-th/0502058. The volume
is exponentially large, leading to a range of string scales from the Planck
mass to the TeV scale, realising for the first time the large extra dimensions
scenario in string theory. We provide a general analysis of the relevance of
perturbative and non-perturbative effects and the regime of validity of the
effective field theory. We compute the spectrum in the moduli sector finding a
hierarchy of masses depending on inverse powers of the volume. We also compute
soft supersymmetry breaking terms for particles living on D3 and D7 branes. We
find a hierarchy of soft terms corresponding to `volume dominated' F-term
supersymmetry breaking. F-terms for Kahler moduli dominate both those for
dilaton and complex structure moduli and D-terms or other de Sitter lifting
terms. This is the first class of string models in which soft supersymmetry
breaking terms are computed after fixing all geometric moduli. We outline
several possible applications of our results, both for cosmology and
phenomenology and point out the differences with the less generic KKLT vacua.Comment: 64 pages, 4 figures; v2. references added; v3. typos, reference
added, matches published versio
Unveiling the origin of X-ray flares in Gamma-Ray Bursts
We present an updated catalog of 113 X-ray flares detected by Swift in the
~33% of the X-ray afterglows of Gamma-Ray Bursts (GRB). 43 flares have a
measured redshift. For the first time the analysis is performed in 4 different
X-ray energy bands, allowing us to constrain the evolution of the flare
temporal properties with energy. We find that flares are narrower at higher
energies: their width follows a power-law relation w~E^{-0.5} reminiscent of
the prompt emission. Flares are asymmetric structures, with a decay time which
is twice the rise time on average. Both time scales linearly evolve with time,
giving rise to a constant rise-to-decay ratio: this implies that both time
scales are stretched by the same factor. As a consequence, the flare width
linearly evolves with time to larger values: this is a key point that clearly
distinguishes the flare from the GRB prompt emission. The flare 0.3-10 keV peak
luminosity decreases with time, following a power-law behaviour with large
scatter: L_{pk}~ t_{pk}^{-2.7}. When multiple flares are present, a global
softening trend is established: each flare is on average softer than the
previous one. The 0.3-10 keV isotropic energy distribution is a log-normal
peaked at 10^{51} erg, with a possible excess at low energies. The flare
average spectral energy distribution (SED) is found to be a power-law with
spectral energy index beta~1.1. These results confirmed that the flares are
tightly linked to the prompt emission. However, after considering various
models we conclude that no model is currently able to account for the entire
set of observations.Comment: MNRAS submitte
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