283 research outputs found
The spectrum of tachyons in AdS/CFT
We analyze the spectrum of open strings stretched between a D-brane and an
anti-D-brane in planar AdS/CFT using various tools. We focus on open strings
ending on two giant gravitons with different orientation in
and study the spectrum of string excitations using the following approaches:
open spin-chain, boundary asymptotic Bethe ansatz and boundary thermodynamic
Bethe ansatz (BTBA). We find agreement between a perturbative high order
diagrammatic calculation in SYM and the leading finite-size
boundary Luscher correction. We study the ground state energy of the system at
finite coupling by deriving and numerically solving a set of BTBA equations.
While the numerics give reasonable results at small coupling, they break down
at finite coupling when the total energy of the string gets close to zero,
possibly indicating that the state turns tachyonic. The location of the
breakdown is also predicted analytically.Comment: 40 pages, lots of figures, v2: typos corrected, accepted for
publication in JHE
Cluster: Mission Overview and End-of-Life Analysis
The Cluster mission is part of the scientific programme of the European Space Agency (ESA) and its purpose is the analysis of the Earth's magnetosphere. The Cluster project consists of four satellites. The selected polar orbit has a shape of 4.0 and 19.2 Re which is required for performing measurements near the cusp and the tail of the magnetosphere. When crossing these regions the satellites form a constellation which in most of the cases so far has been a regular tetrahedron. The satellite operations are carried out by the European Space Operations Centre (ESOC) at Darmstadt, Germany. The paper outlines the future orbit evolution and the envisaged operations from a Flight Dynamics point of view. In addition a brief summary of the LEOP and routine operations is included beforehand
High seroprevalence of feline morbilliviruses in free-roaming domestic cats in Chile
Feline morbillivirus infections have gained increased attention due to repeated reports of their association with urinary tract disease in cats. In the present study, 112 serum samples from free-roaming domestic cats in Chile were tested for antibodies against feline morbillivirus genotypes 1 and 2 (FeMV-1 and FeMV-2) using an indirect immunofluorescence assay. In total, 63% of the animals showed antibodies against one or both FeMV genotypes. Antibodies directed exclusively against FeMV-2 were significantly more prevalent in male cats. The correlation of sex and FeMV-2 infection might give insight into potential routes of transmission. We provide, for the first time, serological data on FeMV in Chile
Black strings in AdS_5
We present non-extremal magnetic black string solutions in five-dimensional
gauged supergravity. The conformal infinity is the product of time and S^1xS_h,
where S_h denotes a compact Riemann surface of genus h. The construction is
based on both analytical and numerical techniques. We compute the holographic
stress tensor, the Euclidean action and the conserved charges of the solutions
and show that the latter satisfy a Smarr-type formula. The phase structure is
determined in the canonical ensemble, and it is shown that there is a first
order phase transition from small to large black strings, which disappears
above a certain critical magnetic charge that is obtained numerically. For
another particular value of the magnetic charge, that corresponds to a twisting
of the dual super Yang-Mills theory, the conformal anomalies coming from the
background curvature and those arising from the coupling to external gauge
fields exactly cancel. We also obtain supersymmetric solutions describing waves
propagating on extremal BPS magnetic black strings, and show that they possess
a Siklos-Virasoro reparametrization invariance.Comment: 40 pages, 7 figures, JHEP3. v2: minor corrections, 2 references
added. v3: typos in holographic stress tensor corrected, 3 references adde
Identification of Novel Feline Paramyxoviruses in Guignas (Leopardus guigna) from Chile
The family of paramyxoviruses has received growing attention as several new species have been identified recently, notably two different clusters in domestic cats, designated as feline morbillivirus (FeMV) and feline paramyxovirus (FPaV). Their phylogenetic origin and whether wild felids also harbor these viruses are currently unknown. Kidney samples from 35 guignas (Leopardus guigna), a wild felid from Chile, were investigated for paramyxoviruses using consensus-RT-PCR. In addition, thirteen serum samples of guignas were screened for the presence of FeMV-specific antibodies by an immunofluorescence assay (IFA). Viral RNA was detected in 31% of the kidney samples. Phylogenetic analyses revealed two well-supported clusters, related to isolates from domestic cats, rodents and bats. No significant histopathology changes were recorded in infected guignas. Serology identified two samples which were positive for FeMV-specific antibodies. Our study highlights the diversity of paramyxovirus infections in felids with special emphasis on guignas from Chile
Structural investigation of MOVPE-Grown GaAs on Ge by X-ray techniques
The selection of appropriate characterisation methodologies is vital for analysing and comprehending the sources of defects and their influence on the properties of heteroepitaxially grown III-V layers. In this work we investigate the structural properties of GaAs layers grown by Metal-Organic Vapour Phase Epitaxy (MOVPE) on Ge substrates – (100) with 6⁰ offset towards – under various growth conditions. Synchrotron X-ray topography (SXRT) is employed to investigate the nature of extended linear defects formed in GaAs epilayers. Other X-ray techniques, such as reciprocal space mapping (RSM) and triple axis ω-scans of (00l)-reflections (l = 2, 4, 6) are used to quantify the degree of relaxation and presence of antiphase domains (APDs) in the GaAs crystals. The surface roughness is found to be closely related to the size of APDs formed at the GaAs/Ge heterointerface, as confirmed by X-ray diffraction (XRD), as well as atomic force microscopy (AFM), and transmission electron microscopy (TEM)
Structural investigation of MOVPE-Grown GaAs on Ge by X-ray techniques
The selection of appropriate characterisation methodologies is vital for analysing and comprehending the sources of defects and their influence on the properties of heteroepitaxially grown III-V layers. In this work we investigate the structural properties of GaAs layers grown by Metal-Organic Vapour Phase Epitaxy (MOVPE) on Ge substrates – (100) with 6⁰ offset towards – under various growth conditions. Synchrotron X-ray topography (SXRT) is employed to investigate the nature of extended linear defects formed in GaAs epilayers. Other X-ray techniques, such as reciprocal space mapping (RSM) and triple axis ω-scans of (00l)-reflections (l = 2, 4, 6) are used to quantify the degree of relaxation and presence of antiphase domains (APDs) in the GaAs crystals. The surface roughness is found to be closely related to the size of APDs formed at the GaAs/Ge heterointerface, as confirmed by X-ray diffraction (XRD), as well as atomic force microscopy (AFM), and transmission electron microscopy (TEM)
Adding flavour to the Polchinski-Strassler background
As an extension of holography with flavour, we analyze in detail the
embedding of a D7-brane probe into the Polchinski-Strassler gravity background,
in which the breaking of conformal symmetry is induced by a 3-form flux G_3.
This corresponds to giving masses to the adjoint chiral multiplets. We consider
the N=2 supersymmetric case in which one of the adjoint chiral multiplets is
kept massless while the masses of the other two are equal. This setup requires
a generalization of the known expressions for the backreaction of G_3 in the
case of three equal masses to generic mass values. We work to second order in
the masses to obtain the embedding of D7-brane probes in the background. At
this order, the 2-form potentials corresponding to the background flux induce
an 8-form potential which couples to the worldvolume of the D7-branes. We show
that the embeddings preserve an SU(2) x SU(2) symmetry. We study possible
embeddings both analytically in a particular approximation, as well as
numerically. The embeddings preserve supersymmetry, as we investigate using the
approach of holographic renormalization. The meson spectrum associated to one
of the embeddings found reflects the presence of the adjoint masses by
displaying a mass gap.Comment: LaTeX, 50 pages, 9 figure
Intersecting Flavor Branes
We consider an instance of the AdS/CFT duality where the bulk theory contains
an open string tachyon, and study the instability from the viewpoint of the
boundary field theory. We focus on the specific example of the AdS_5 X S^5
background with two probe D7 branes intersecting at general angles. For generic
angles supersymmetry is completely broken and there is an open string tachyon
between the branes. The field theory action for this system is obtained by
coupling to N =4 super Yang-Mills two N =2 hyper multiplets in the fundamental
representation of the SU(N) gauge group, but with different choices of
embedding of the two N=2 subalgebras into N=4. On the field theory side we find
a one-loop Coleman-Weinberg instability in the effective potential for the
fundamental scalars. We identify a mesonic operator as the dual of the open
string tachyon. By AdS/CFT, we predict the tachyon mass for small 't Hooft
coupling (large bulk curvature) and confirm that it violates the AdS stability
bound.Comment: 36 page
Four-loop anomalous dimensions in Leigh-Strassler deformations
We determine the scalar part of the four-loop chiral dilatation operator for
Leigh-Strassler deformations of N=4 super Yang-Mills. This is sufficient to
find the four-loop anomalous dimensions for operators in closed scalar
subsectors. This includes the SU(2) subsector of the (complex)
beta-deformation, where we explicitly compute the anomalous dimension for
operators with a single impurity. It also includes the "3-string null"
operators of the cubic Leigh-Strassler deformation. Our four-loop results show
that the rational part of the anomalous dimension is consistent with a
conjecture made in arXiv:1108.1583 based on the three-loop result of
arXiv:1008.3351 and the N=4 magnon dispersion relation. Here we find additional
zeta(3) terms.Comment: Latex, feynmp, 21 page
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