Fluxes, supersymmetry breaking and gauged supergravity

We report on the gauged supergravity interpretation of certain compactifications of superstring theories with p-form fluxes turned on. We discuss in particular the interplay of duality symmetries in type IIB orientifolds and gauged isometries in the corresponding supergravity models. Turning on fluxes is generally described by the gauging of some nilpotent Lie group whose generators correspond to axion symmetries of R-R and N-S scalars.Comment: Contribution to the proceedings of ``Sugra20'' Conference, Department of Physics, Northeastern University, Boston (Ma) 02115 USA; March 200

Regular R-R and NS-NS BPS black holes

We show in a precise group theoretical fashion how the generating solution of regular BPS black holes of N=8 supergravity, which is known to be a solution also of a simpler N=2 STU model truncation, can be characterized as NS-NS or R-R charged according to the way the corresponding STU model is embedded in the original N=8 theory. Of particular interest is the class of embeddings which yield regular BPS black hole solutions carrying only R-R charge and whose microscopic description can possibly be given in terms of bound states of D-branes only. The microscopic interpretation of the bosonic fields in this class of STU models relies on the solvable Lie algebra (SLA) method. In the present article we improve this mathematical technique in order to provide two distinct descriptions for type IIA and type IIB theories and an algebraic characterization of S*T--dual embeddings within the N=8,d=4 theory. This analysis will be applied to the particular example of a four parameter (dilatonic) solution of which both the full macroscopic and microscopic descriptions will be worked out.Comment: latex, 30 pages. Final version to appear on Int.J.Mod.Phy

Observations on the Partial Breaking of N=2N=2 Rigid Supersymmetry

We study the partial breaking of $N=2$ rigid supersymmetry for a generic rigid special geometry of $n$ abelian vector multiplets in the presence of Fayet-Iliopoulos terms induced by the Hyper-K\"ahler momentum map. By exhibiting the symplectic structure of the problem we give invariant conditions for the breaking to occur, which rely on a quartic invariant of the Fayet-Iliopoulos charges as well as on a modification of the $N=2$ rigid symmetry algebra by a vector central charge.Comment: 7 pages, LaTeX sourc

Dualities Near the Horizon

In 4-dimensional supergravity theories, covariant under symplectic electric-magnetic duality rotations, a significant role is played by the symplectic matrix M({\phi}), related to the coupling of scalars {\phi} to vector field-strengths. In particular, this matrix enters the twisted self-duality condition for 2-form field strengths in the symplectic formulation of generalized Maxwell equations in the presence of scalar fields. In this investigation, we compute several properties of this matrix in relation to the attractor mechanism of extremal (asymptotically flat) black holes. At the attractor points with no flat directions (as in the N = 2 BPS case), this matrix enjoys a universal form in terms of the dyonic charge vector Q and the invariants of the corresponding symplectic representation RQ of the duality group G, whenever the scalar manifold is a symmetric space with G simple and non-degenerate of type E7. At attractors with flat directions, M still depends on flat directions, but not MQ, defining the so-called Freudenthal dual of Q itself. This allows for a universal expression of the symplectic vector field strengths in terms of Q, in the near-horizon Bertotti-Robinson black hole geometry.Comment: 1+31 pages, 1 Table; v2 : completely reorganized (and shortened) structure, some Sections removed; various clarifications, formulae, and Refs. added; to appear on JHE

C-map for Born-Infeld theories

The c-map of four dimensional non-linear theories of electromagnetism is considered both in the rigid case and in its coupling to gravity. In this way theories with antisymmetric tensors and scalars are obtained, and the three non-linear representations of N=2 supersymmetry partially broken to N=1 related. The manifest $\mathrm{Sp}(2n)$ and $\mathrm{U}(n)$ covariance of these theories in their multifield extensions is also exhibited.Comment: Version to appear on Physics Letters

Extremal Black Holes in Supergravity

We present the main features of the physics of extremal black holes embedded in supersymmetric theories of gravitation, with a detailed analysis of the attractor mechanism for BPS and non-BPS black-hole solutions in four dimensions.Comment: Typos corrected, some points clarifie

A Search for an N=2 Inflaton Potential

We consider N=2 supergravity theories that have the same spectrum as the R+R^2 supergravity, as predicted from the off-shell counting of degrees of freedom. These theories describe standard N=2 supergravity coupled to one or two long massive vector multiplets. The central charge is not gauged in these models and they have a Minkowski vacuum with N=2 unbroken supersymmetry. The gauge symmetry, being non-compact, is always broken. $\alpha$-deformed inflaton potentials are obtained, in the case of a single massive vector multiplet, with $\alpha=1/3$ and $2/3$. The $\alpha=1$ potential (i.e. the Starobinsky potential) is also obtained, but only at the prize of having a single massive vector and a residual unbroken gauge symmetry. The inflaton corresponds to one of the Cartan fields of the non-compact quaternionic-K{\"a}hler cosets.Comment: 32 pages, 1 figure, LaTeX source, typos correcte

Structural Health Monitoring Issues Using Inclinometers on Prestressed Concrete Girder Bridge Decks

In the last decades, assessment and rehabilitation of the existing built environment constitute one of the major challenges for engineers, practitioners and code-makers all over the world. Aging, deterioration processes, lack of or improper maintenance, and increasing occurrence of extreme events have led to the need of more efficient methods for the safety assessment and retrofitting/rehabilitation of existing concrete structures like bridges. New approaches deriving from research should be able to provide solutions devoted to reduce and/or avoid the necessity of interventions, verifying the safety conditions for human life and performances for serviceability on aged infrastructures. Structural Health Monitoring (SHM) of existing bridges has become a key issue in all western world as most of the infrastructures of each Country are reaching the end of their design life. SHM can be divided classically in two approaches: static and dynamic. Static SHM is based on the measure of displacements and their derivatives like rotations or strains regardless of the dynamic behaviour of the structure. Clinometers are among the most used devices to measure angles on structures; they can provide high accuracy when used in static mode as advanced techniques of signal processing can be used to reduce the noise of the signal working on acquisitions that can last several seconds to provide one single accurate measure of angle. Nevertheless, many issues one the affidability and the correct use of measures done with clinometers have to be addressed to achieve a trustworthy SHM using such devices. In this paper the most relevant issues related to the f.e.m. modelling of a bridge deck in view of the use of clinometers for SHM are presented providing explanation using a test case bridge that has been under continuous investigation for many months. A brief explanation of the process for data cleaning and interpretation is also given, stressing out the limits of the technology and the possible outcomes

Tianjin Binhai Library

Tianjin Binhai Library MVRDV Work Tianjin Binhai Library Location Tianjin, China Mainland Project Year 2017 Architecture and Design MVRDV, Tianjin Urban Planning and Design Institute (TUPDI) Project Team Lighting Design: Huayi Jianyuan lighting design Interior Architect: TADI Engineering Sanjiang Steel Structure Design Size and total area 33.700 m2 Image credits Mario Ferrar

N=8 gaugings revisited: an exhaustive classification

In this paper we reconsider, for N=8 supergravity, the problem of gauging the most general electric subgroup. We show that admissible theories are fully characterized by a single algebraic equation to be satisfied by the embedding of the gauge group G within the electric subalgebra SL(8,\IR) of E_{7(7)}. The complete set of solutions to this equation contains 36 parameters. Modding by the action of SL(8,\IR) conjugations that yield equivalent theories all continuous parameters are eliminated except for an overall coupling constant and we obtain a discrete set of orbits. This set is in one--to--one correspondence with 36 Lie subalgebras of SL(8,\IR), corresponding to all possible real forms of the SO(8) Lie algebra plus a set of contractions thereof. By means of our analysis we establish the theorem that the N=8 gaugings constructed by Hull in the middle eighties constitute the exhaustive set of models. As a corollary we show that there exists a unique 7--dimensional abelian gauging. The corresponding abelian algebra is not contained in the maximal abelian ideal of the solvable Lie algebra generating the scalar manifold E_{7(7)}/SU(8).Comment: 1 LaTeX file, 41 pages, 3 eps-figure