34 research outputs found
Constraints for the existence of flat and stable non-supersymmetric vacua in supergravity
We further develop on the study of the conditions for the existence of
locally stable non-supersymmetric vacua with vanishing cosmological constant in
supergravity models involving only chiral superfields. Starting from the two
necessary conditions for flatness and stability derived in a previous paper
(which involve the Kahler metric and its Riemann tensor contracted with the
supersymmetry breaking auxiliary fields) we show that the implications of these
constraints can be worked out exactly not only for factorizable scalar
manifolds, but also for symmetric coset manifolds. In both cases, the
conditions imply a strong restriction on the Kahler geometry and constrain the
vector of auxiliary fields defining the Goldstino direction to lie in a certain
cone. We then apply these results to the various homogeneous coset manifolds
spanned by the moduli and untwisted matter fields arising in string
compactifications, and discuss their implications. Finally, we also discuss
what can be said for completely arbitrary scalar manifolds, and derive in this
more general case some explicit but weaker restrictions on the Kahler geometry.Comment: 22 pages, Latex, no figure
Thermodynamics of the localized D2-D6 system
An exact fully-localized extremal supergravity solution for N_2 D2 branes and
N_6 D6 branes, which is dual to 3-dimensional supersymmetric SU(N_2) gauge
theory with N_6 fundamentals, was found by Cherkis and Hashimoto. In order to
consider the thermal properties of the gauge theory we present the non-extremal
extension of this solution to first order in an expansion near the core of the
D6 branes. We compute the Hawking temperature and the black brane horizon
area/entropy. The leading order entropy, which is proportional to N_2^{3/2}
N_6^{1/2} T_H^2, is not corrected to first order in the expansion. This result
is consistent with the analogous weak-coupling result at the correspondence
point N_2 ~ N_6.Comment: 14 page
Metastable supergravity vacua with F and D supersymmetry breaking
We study the conditions under which a generic supergravity model involving
chiral and vector multiplets can admit viable metastable vacua with
spontaneously broken supersymmetry and realistic cosmological constant. To do
so, we impose that on the vacuum the scalar potential and all its first
derivatives vanish, and derive a necessary condition for the matrix of its
second derivatives to be positive definite. We study then the constraints set
by the combination of the flatness condition needed for the tuning of the
cosmological constant and the stability condition that is necessary to avoid
unstable modes. We find that the existence of such a viable vacuum implies a
condition involving the curvature tensor for the scalar geometry and the charge
and mass matrices for the vector fields. Moreover, for given curvature, charges
and masses satisfying this constraint, the vector of F and D auxiliary fields
defining the Goldstino direction is constrained to lie within a certain domain.
The effect of vector multiplets relative to chiral multiplets is maximal when
the masses of the vector fields are comparable to the gravitino mass. When the
masses are instead much larger or much smaller than the gravitino mass, the
effect becomes small and translates into a correction to the effective
curvature. We finally apply our results to some simple classes of examples, to
illustrate their relevance.Comment: 40 pages; v2 some clarifications added in the introduction; v3 some
typos correcte
N=2 supersymmetric gauge theories with massive hypermultiplets and the Whitham hierarchy
We embed the Seiberg-Witten solution for the low energy dynamics of N=2 super
Yang-Mills theory with an even number of massive hypermultiplets into the
Whitham hierarchy. Expressions for the first and second derivatives of the
prepotential in terms of the Riemann theta function are provided which extend
previous results obtained by Gorsky, Marshakov, Mironov and Morozov. Checks in
favour of the new equations involve both their behaviour under duality
transformations and the consistency of their semiclassical expansions.Comment: 37 pages, LaTeX2e, no figures; references adde
Instanton corrections in N=2 supersymmetric theories with classical gauge groups and fundamental matter hypermultiplets
We compute instanton corrections to the low energy effective prepotential of
N=2 supersymmetric theories in a variety of cases, including all classical
gauge groups and even number of fundamental matter hypermultiplets. To this
end, we take profit of a set of first- and second-order equations for the
logarithmic derivatives of the prepotential with respect to the dynamical scale
expressed in terms of Riemann's theta-function. These equations emerge in the
context of the Whitham hierarchy approach to the low-energy Seiberg--Witten
solution of supersymmetric gauge theories. Our procedure is recursive and
allows to compute the effective prepotential to arbitrary order in a remarkably
straightforward way. General expressions for up to three-instanton corrections
are given. We illustrate the method with explicit expressions for several
cases.Comment: 25 pages, LaTeX2e, no figures; v2: Concluding remarks expanded, other
minor changes. Final version to be published in Nuclear Physics
Prepotential and Instanton Corrections in N=2 Supersymmetric SU(N_1)xSU(N_2) Yang Mills Theories
In this paper we analyse the non-hyperelliptic Seiberg-Witten curves derived
from M-theory that encode the low energy solution of N=2 supersymmetric
theories with product gauge groups. We consider the case of a SU(N_1)xSU(N_2)
gauge theory with a hypermultiplet in the bifundamental representation together
with matter in the fundamental representations of SU(N_1) and SU(N_2). By means
of the Riemann bilinear relations that hold on the Riemann surface defined by
the Seiberg--Witten curve, we compute the logarithmic derivative of the
prepotential with respect to the quantum scales of both gauge groups. As an
application we develop a method to compute recursively the instanton
corrections to the prepotential in a straightforward way. We present explicit
formulas for up to third order on both quantum scales. Furthermore, we extend
those results to SU(N) gauge theories with a matter hypermultiplet in the
symmetric and antisymmetric representation. We also present some non-trivial
checks of our results.Comment: 21 pages, 2 figures, minor changes and references adde
Inflating in a Better Racetrack
We present a new version of our racetrack inflation scenario which, unlike
our original proposal, is based on an explicit compactification of type IIB
string theory: the Calabi-Yau manifold P^4_[1,1,1,6,9]. The axion-dilaton and
all complex structure moduli are stabilized by fluxes. The remaining 2 Kahler
moduli are stabilized by a nonperturbative superpotential, which has been
explicitly computed. For this model we identify situations for which a linear
combination of the axionic parts of the two Kahler moduli acts as an inflaton.
As in our previous scenario, inflation begins at a saddle point of the scalar
potential and proceeds as an eternal topological inflation. For a certain range
of inflationary parameters, we obtain the COBE-normalized spectrum of metric
perturbations and an inflationary scale of M = 3 x 10^{14} GeV. We discuss
possible changes of parameters of our model and argue that anthropic
considerations favor those parameters that lead to a nearly flat spectrum of
inflationary perturbations, which in our case is characterized by the spectral
index n_s = 0.95.Comment: 20 pages, 7 figures. Brief discussion on the non-gaussianity of this
model, one more figure of the field trajectories added as well as other minor
changes to the tex
Higher COVID-19 pneumonia risk associated with anti-IFN-α than with anti-IFN-Ï auto-Abs in children
We found that 19 (10.4%) of 183 unvaccinated children hospitalized for COVID-19 pneumonia had autoantibodies (auto-Abs) neutralizing type I IFNs (IFN-alpha 2 in 10 patients: IFN-alpha 2 only in three, IFN-alpha 2 plus IFN-omega in five, and IFN-alpha 2, IFN-omega plus IFN-beta in two; IFN-omega only in nine patients). Seven children (3.8%) had Abs neutralizing at least 10 ng/ml of one IFN, whereas the other 12 (6.6%) had Abs neutralizing only 100 pg/ml. The auto-Abs neutralized both unglycosylated and glycosylated IFNs. We also detected auto-Abs neutralizing 100 pg/ml IFN-alpha 2 in 4 of 2,267 uninfected children (0.2%) and auto-Abs neutralizing IFN-omega in 45 children (2%). The odds ratios (ORs) for life-threatening COVID-19 pneumonia were, therefore, higher for auto-Abs neutralizing IFN-alpha 2 only (OR [95% CI] = 67.6 [5.7-9,196.6]) than for auto-Abs neutralizing IFN-. only (OR [95% CI] = 2.6 [1.2-5.3]). ORs were also higher for auto-Abs neutralizing high concentrations (OR [95% CI] = 12.9 [4.6-35.9]) than for those neutralizing low concentrations (OR [95% CI] = 5.5 [3.1-9.6]) of IFN-omega and/or IFN-alpha 2