1,268 research outputs found
From ten to four and back again: how to generalize the geometry
We discuss the four-dimensional N=1 effective approach in the study of warped
type II flux compactifications with SU(3)x SU(3)-structure to AdS_4 or flat
Minkowski space-time. The non-trivial warping makes it natural to use a
supergravity formulation invariant under local complexified Weyl
transformations. We obtain the classical superpotential from a standard
argument involving domain walls and generalized calibrations and show how the
resulting F-flatness and D-flatness equations exactly reproduce the full
ten-dimensional supersymmetry equations. Furthermore, we consider the effect of
non-perturbative corrections to this superpotential arising from gaugino
condensation or Euclidean D-brane instantons. For the latter we derive the
supersymmetry conditions in N=1 flux vacua in full generality. We find that the
non-perturbative corrections induce a quantum deformation of the internal
generalized geometry. Smeared instantons allow to understand KKLT-like AdS
vacua from a ten-dimensional point of view. On the other hand, non-smeared
instantons in IIB warped Calabi-Yau compactifications 'destabilize' the
Calabi-Yau complex structure into a genuine generalized complex one. This
deformation gives a geometrical explanation of the non-trivial superpotential
for mobile D3-branes induced by the non-perturbative corrections.Comment: LaTeX, 47 pages, v2, references, hyperref added, v3, correcting small
inaccuracies in eqs. (2.6a) and (5.16
The energy and stability of D-term strings
Cosmic strings derived from string theory, supergravity or any theory of
choice should be stable if we hope to observe them. In this paper we consider
D-term strings in D=4, N=1 supergravity with a constant Fayet-Iliopoulos term.
We show that the positive deficit angle supersymmetric D-term string is
non-perturbatively stable by using standard Witten-Nester techniques to prove a
positive energy theorem. Particular attention is paid to the negative deficit
angle D-term string, which is known to violate the dominant energy condition.
Within the class of string solutions we consider, this violation implies that
the negative deficit angle D-term string must have a naked pathology and
therefore the positive energy theorem we prove does not apply to it. As an
interesting aside, we show that the Witten-Nester charge calculates the total
gravitational energy of the D-term string without the need for a cut-off, which
may not have been expected.Comment: 18 pages. v2: minor changes and references adde
Dirac equation for the supermembrane in a background with fluxes from a component description of the D=11 supergravity-supermembrane interacting system
We present a simple derivation of the 'Dirac' equation for the supermembrane
fermionic field in a D=11 supergravity background with fluxes by using a
complete but gauge-fixed description of the supergravity-supermembrane
interacting system previously developed. We also discuss the contributions
linear in the supermembrane fermions -the Goldstone fields for the local
supersymmetry spontaneously broken by the superbrane- to the field equations of
the supergravity-supermembrane interacting system. The approach could also be
applied to more complicated dynamical systems such as those involving the
M5-brane and the D=10 Dirichlet branes.Comment: 1+22 pages, JHEP style. v2: cosmetic changes and references added to
conform to the JHEP published versio
Flavor brane on the baryonic branch of moduli space
We study an extra flavor in the cascading SU((k+1)M)xSU(k M) gauge theory by
adding probe D7-brane to the geometry. By finding a solution to the
kappa-symmetry equation we establish that the D7-brane is mutually
supersymmetric with the background everywhere on the baryonic branch of moduli
space. We also discuss possible applications of this result.Comment: 15 pages; v2 typo corrected, references adde
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
Statistical trend analysis and extreme distribution of significant wave height from 1958 to 1999 – an application to the Italian Seas
The study is a statistical analysis of sea states timeseries derived using the wave model WAM forced by the ERA-40 dataset in selected areas near the Italian coasts. For the period 1 January 1958 to 31 December 1999 the analysis yields: (i) the existence of a negative trend in the annual- and winter-averaged sea state heights; (ii) the existence of a turning-point in late 80's in the annual-averaged trend of sea state heights at a site in the Northern Adriatic Sea; (iii) the overall absence of a significant trend in the annual-averaged mean durations of sea states over thresholds; (iv) the assessment of the extreme values on a time-scale of thousand years. The analysis uses two methods to obtain samples of extremes from the independent sea states: the <i>r-largest annual maxima</i> and the <i>peak-over-threshold</i>. The two methods show statistical differences in retrieving the return values and more generally in describing the significant wave field. The <i>r-largest annual maxima</i> method provides more reliable predictions of the extreme values especially for small return periods (&lt;100 years). Finally, the study statistically proves the existence of decadal negative trends in the significant wave heights and by this it conveys useful information on the wave climatology of the Italian seas during the second half of the 20th century
Wilson Loop, Regge Trajectory and Hadron Masses in a Yang-Mills Theory from Semiclassical Strings
We compute the one-loop string corrections to the Wilson loop, glueball Regge
trajectory and stringy hadron masses in the Witten model of non supersymmetric,
large-N Yang-Mills theory. The classical string configurations corresponding to
the above field theory objects are respectively: open straight strings, folded
closed spinning strings, and strings orbiting in the internal part of the
supergravity background. For the rectangular Wilson loop we show that besides
the standard Luescher term, string corrections provide a rescaling of the field
theory string tension. The one-loop corrections to the linear glueball Regge
trajectories render them nonlinear with a positive intercept, as in the
experimental soft Pomeron trajectory. Strings orbiting in the internal space
predict a spectrum of hadronic-like states charged under global flavor
symmetries which falls in the same universality class of other confining
models.Comment: 52 pages, latex 3 times, v3: references adde
Open String Wavefunctions in Warped Compactifications
We analyze the wavefunctions for open strings in warped compactifications,
and compute the warped Kahler potential for the light modes of a probe D-brane.
This analysis not only applies to the dynamics of D-branes in warped
backgrounds, but also allows to deduce warping corrections to the closed string
Kahler metrics via their couplings to open strings. We consider in particular
the spectrum of D7-branes in warped Calabi-Yau orientifolds, which provide a
string theory realizations of the Randall-Sundrum scenario. We find that
certain background fluxes, necessary in the presence of warping, couple to the
fermionic wavefunctions and qualitatively change their behavior. This modified
dependence of the wavefunctions are needed for consistency with supersymmetry,
though it is present in non-supersymmetric vacua as well. We discuss the
deviations of our setup from the RS scenario and, as an application of our
results, compute the warping corrections to Yukawa couplings in a simple model.
Our analysis is performed both with and without the presence of D-brane
world-volume flux, as well as for the case of backgrounds with varying dilaton.Comment: 52 pages, refs. added, minor correction
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