511 research outputs found
N=2 Super-Higgs, N=1 Poincare' Vacua and Quaternionic Geometry
In the context of N=2 supergravity we explain the occurrence of partial
super-Higgs with vanishing vacuum energy and moduli stabilization in a model
suggested by superstring compactifications on type IIB orientifolds with 3-form
fluxes.
The gauging of axion symmetries of the quaternionic manifold, together with
the use of degenerate symplectic sections for special geometry, are the
essential ingredients of the construction.Comment: 18 page
Axion gauge symmetries and generalized Chern-Simons terms in N=1 supersymmetric theories
We compute the form of the Lagrangian of N=1 supersymmetric theories with
gauged axion symmetries. It turns out that there appear generalized
Chern-Simons terms that were not considered in previous superspace formulations
of general N=1 theories. Such gaugings appear in supergravities arising from
flux compactifications of superstrings, as well as from Scherk-Schwarz
generalized dimensional reduction in M-theory. We also present the dual
superspace formulation where axion chiral multiplets are dualized into linear
multiplets.Comment: References added and few misprints correcte
Open Heterotic Strings
We classify potential cosmic strings according to the topological charge
measurable outside the string core. We conjecture that in string theory it is
this charge that governs the stability of long strings. This would imply that
the SO(32) heterotic string can have endpoints, but not the E_8 x E_8 heterotic
string. We give various arguments in support of this conclusion.Comment: 15 pages. v.2: typos, references correcte
Non-existence of a dilaton gravity action for the exact string black hole
We prove that no local diffeomorphism invariant two-dimensional theory of the
metric and the dilaton without higher derivatives can describe the exact string
black hole solution found a decade ago by Dijkgraaf, Verlinde and Verlinde. One
of the key points in this proof is the concept of dilaton-shift invariance. We
present and solve (classically) all dilaton-shift invariant theories of
two-dimensional dilaton gravity. Two such models, resembling the exact string
black hole and generalizing the CGHS model, are discussed explicitly.Comment: 24 pages, 3 eps-figures, revised version (more references, clarified
some of the discussion
N=4 Supergravity Lagrangian for Type IIB Orientifold on T^6/Z_2 in Presence of Fluxes and D3-Branes
We derive the Lagrangian and the transformation laws of N=4 gauged
supergravity coupled to matter multiplets whose sigma-model of the scalars is
SU(1,1)/U(1)x SO(6,6+n)/SO(6)xSO(6+n) and which corresponds to the effective
Lagrangian of the Type IIB string compactified on the T^6/Z_2 orientifold with
fluxes turned on and in presence of n D3-branes. The gauge group is T^12 x G
where G is the gauge group on the brane and T^12 is the gauge group on the bulk
corresponding to the gauged translations of the R-R scalars coming from the R-R
four--form. The N=4 bulk sector of this theory can be obtained as a truncation
of the Scherk-Schwarz spontaneously broken N=8 supergravity. Consequently the
full bulk spectrum satisfies quadratic and quartic mass sum rules, identical to
those encountered in Scherk-Schwarz reduction gauging a flat group. This theory
gives rise to a no scale supergravity extended with partial super-Higgs
mechanism.Comment: 49 pages, LaTex, 2 figures. Misprints corrected, more comments adde
String Theoretic Bounds on Lorentz-Violating Warped Compactification
We consider warped compactifications that solve the 10 dimensional
supergravity equations of motion at a point, stabilize the position of a
D3-brane world, and admit a warp factor that violates Lorentz invariance along
the brane. This gives a string embedding of ``asymmetrically warped'' models
which we use to calculate stringy (\alpha') corrections to standard model
dispersion relations, paying attention to the maximum speeds for different
particles. We find, from the dispersion relations, limits on gravitational
Lorentz violation in these models, improving on current limits on the speed of
graviton propagation, including those derived from field theoretic loops. We
comment on the viability of models that use asymmetric warping for self-tuning
of the brane cosmological constant.Comment: 20pg, JHEP3; v2 additional references, slight change to intro; v3.
added referenc
4-D gauged supergravity analysis of Type IIB vacua on
We analyze vacua of type IIB string theory on in
presence of three-form fluxes from a four dimensional supergravity viewpoint.
The quaternionic geometry of the moduli space together with the special
geometry of the NS and R-R dilatons and of the -complex structure moduli
play a crucial role in the analysis. The introduction of fluxes corresponds to
a particular gauging of N=2, D=4 supergravity. Our results agree with a recent
work of Tripathy and Trivedi. The present formulation shows the power of
supergravity in the study of effective theories with broken supersymmetry.Comment: AMS-LaTeX, 29 page
User-informed marketing versus standard description to drive demand for evidence-based therapy: A randomized controlled trial.
Direct-to-consumer (DTC) marketing represents a vital strategy to disseminate evidence-based therapies (EBTs). This 3-phase research program, informed by the marketing mix, developed and evaluated user-informed DTC materials for parents concerned about adolescent substance use (SU). Phases 1 and 2 consisted of qualitative interviews (n = 29 parents) and a quantitative survey (n = 411), respectively, to elicit parents’ preferred terms and strategies to disseminate EBT. Building upon prior phases, the current study (Phase 3) developed a user-informed infographic (128 words, 7th-grade level) focused on SU therapy. Parents were randomly assigned to view the user-informed infographic (n = 75) or a standard EBT description (n = 77) from the American Psychological Association (529 words, 12th-grade level). Logistic regressions examined the effect of marketing condition on parent-reported behavioral intentions and actual requests for EBT information, controlling for correlates of parent preferences in Phase 2 (parent education level; adolescent internalizing, externalizing, legal, and SU problems). Counter to hypotheses, condition did not have a main effect on either outcome. However, there was a significant interaction between condition and adolescent SU problems: among parents whose adolescents had SU problems, the user-informed infographic predicted 3.7 times higher odds of requesting EBT information than the standard description. Additionally, parents whose adolescents had legal problems were more likely to request EBT information than parents whose adolescents did not. The infographic was 4 times shorter and written at 5 grade levels lower, thereby providing a highly disseminable alternative. Findings highlight the value of specificity in DTC marketing, while advancing methods to create tailored marketing materials and communicate knowledge about psychological science
N=3 Warped Compactifications
Orientifolds with three-form flux provide some of the simplest string
examples of warped compactification. In this paper we show that some models of
this type have the unusual feature of D=4, N=3 spacetime supersymmetry. We
discuss their construction and low energy physics. Although the local form of
the moduli space is fully determined by supersymmetry, to find its global form
requires a careful study of the BPS spectrum.Comment: 27 pages, v2: 32pp., RevTeX4, fixed factors, slightly improved
sections 3D and 4B, v3: added referenc
Can a CPT Violating Ether Solve ALL Electron (Anti)Neutrino Puzzles?
Assuming that CPT is violated in the neutrino sector seems to be a viable
alternative to sterile neutrinos when it comes to reconciling the LSND anomaly
with the remainder of the neutrino data. There are different (distinguishable)
ways of incorporating CPT violation into the standard model, including
postulating m different from \bar{m}. Here, I investigate the possibility of
introducing CPT violation via Lorentz-invariance violating effective operators
(``Ether'' potentials) which modify neutrino oscillation patterns like ordinary
matter effects. I argue that, within a simplified two-flavor like oscillation
analysis, one cannot solve the solar neutrino puzzle and LSND anomaly while
still respecting constraints imposed by other neutrino experiments, and comment
on whether significant improvements should be expected from a three-flavor
analysis. If one turns the picture upside down, some of the most severe
constrains on such CPT violating terms can already be obtained from the current
neutrino data, while much more severe constraints can arise from future
neutrino oscillation experiments.Comment: 10 pages, 1 eps figure; version to appear in PRD. Comment added,
mistake corrected, results and conclusions unchange
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