arXiv subjects

M. Trigiante

Publications and source records attributed to M. Trigiante.

At least 55 records · Page 3Linked to original sources

arXiv2005

E_{7(7)} symmetry and dual gauge algebra of M-theory on a twisted seven-torus

We consider M-theory compactified on a twisted 7-torus with fluxes when all the seven antisymmetric tensor fields in four dimensions have been dualized into scalars and thus the E_{7(7)} symmetry is recovered. We find that the Scherk--Schwarz and flux gaugings define a ``dual'' gauge algebra, subalgbra of E_{7(7)}, where some of the generators are associated with vector fields which are dual to part of the original vector fields (deriving from the 3-form). In particular they are dual to those vector fields which have been ``eaten'' by the antisymmetric tensors in the original theory by the (anti-)Higgs mechanism. The dual gauge algebra coincides with the original gauge structure when the quotient with respect to these dual (broken) gauge generators is taken. The particular example of the S-S twist corresponding to a ``flat group'' is considered.

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arXiv2005

N=1 reductions of N=2 supergravity in the presence of tensor multiplets

We consider consistent truncations of N=2 supergravites in the presence of tensor multiplets (dual to hypermultiplets) as they occur in type IIB compactifications on Calabi--Yau orientifolds. We analyze in detail the scalar potentials encompassing these reductions when fluxes are turned on and study vacua of the N=1 phases.

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arXiv2004

Gauging the Heisenberg algebra of special quaternionic manifolds

We show that in N=2 supergravity, with a special quaternionic manifold of (quaternionic) dimension h_1+1 and in the presence of h_2 vector multiplets, a h_2+1 dimensional abelian algebra, intersecting the 2h_1+3 dimensional Heisenberg algebra of quaternionic isometries, can be gauged provided the h_2+1 symplectic charge--vectors V_I, have vanishing symplectic invariant scalar product V_I X V_J=0. For compactifications on Calabi--Yau three--folds with Hodge numbers (h_1,h_2) such condition generalizes the half--flatness condition as used in the recent literature. We also discuss non--abelian extensions of the above gaugings and their consistency conditions.

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arXiv2004

Orientifolds, Brane Coordinates and Special Geometry

We report on the gauged supergravity analysis of Type IIB vacua on K3x T2/Z2 orientifold in the presence of D3-D7-branes and fluxes. We discuss supersymmetric critical points correspond to Minkowski vacua and the related fixing of moduli, finding agreement with previous analysis. An important role is played by the choice of the symplectic holomorphic sections of special geometry which enter the computation of the scalar potential. The related period matrix N is explicitly given. The relation between the special geometry and the Born--Infeld action for the brane moduli is elucidated.

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arXiv2004

c--Map,very Special Quaternionic Geometry and Dual Kahler Spaces

We show that for all very special quaternionic manifolds a different N=1 reduction exists, defining a Kaehler Geometry which is ``dual'' to the original very special Kaehler geometry with metric G_{a\bar{b}}= - \partial_a \partial_b \ln V (V={1/6}d_{abc}λ^a λ^b λ^c). The dual metric g^{ab}=V^{-2} (G^{-1})^{ab} is Kaehler and it also defines a flat potential as the original metric. Such geometries and some of their extensions find applications in Type IIB compactifications on Calabi--Yau orientifolds.

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arXiv2004

K3 x T^2/Z_2 orientifolds with fluxes, open string moduli and critical points

We extend the four-dimensional gauged supergravity analysis of type IIB vacua on $K3\times T^2/Z_2$ to the case where also D3 and D7 moduli, belonging to N=2 vector multiplets, are turned on. In this case, the overall special geometry does not correspond to a symmetric space, unless D3 or D7 moduli are switched off. In the presence of non--vanishing fluxes, we discuss supersymmetric critical points which correspond to Minkowski vacua, finding agreement with previous analysis. Finally, we point out that care is needed in the choice of the symplectic holomorphic sections of special geometry which enter the computation of the scalar potential.

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arXiv2003

Cosmological backgrounds of superstring theory and Solvable Algebras: Oxidation and Branes

We develop a systematic algorithm to construct, classify and study exact solutions of type II A/B supergravity which are time--dependent and homogeneous and hence represent candidate cosmological backgrounds. Using the formalism of solvable Lie algebras to represent the geometry of non--compact coset manifolds U/H we are able to reduce the supergravity field equations to the geodesic equations in U/H and rephrase these latter in a completely algebraic setup by means of the so called Nomizu operator representation of covariant derivatives in solvable group manifolds. In this way a systematic method of integration of supergravity equations is provided. We show how the possible D=3 solutions are classified by non--compact subalgebras G of E8(8) and their ten--dimensional physical interpretation (oxidation) depends on the classification of the different embeddings of G inside E8(8). We give some preliminary examples of explicit solutions based on the simplest choice G=A2. We also show how, upon oxidation, these solutions provide a smooth and exact realization of the bouncing phenomenon on Weyl chamber walls envisaged by the cosmological billiards of Damour et al. We also show how this physical phenomenon is triggered by the presence of euclidean $D$--branes possibly interpretable at the microscopic level as S--branes. We outline how our analysis could be extended to a wider setup where, by further reducing to $D=2,1$, more general backgrounds could be constructed applying our method to the infinite algebras E9 and E10.

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arXiv2003

Exact solutions for Bianchi type cosmological metrics, Weyl orbits of E_{8(8)} subalgebras and p--branes

In this paper we pursue further a programme initiated in a previous work and aimed at the construction, classification and property investigation of time dependent solutions of supergravity (superstring backgrounds) through a systematic exploitation of U-duality hidden symmetries. This is done by first reducing to D=3 where the bosonic part of the theory becomes a sigma model on E_{8(8)}/SO(16), solving the equations through an algorithm that produces general integrals for any chosen regular subalgebra G_r of E_{8(8)} and then oxiding back to D=10. Different oxidations and hence different physical interpretations of the same solutions are associated with different embeddings of G_r. We show how such embeddings constitute orbits under the Weyl group and we study the orbit space. This is relevant to associate candidate superstring cosmological backgrounds to space Dp-brane configurations that admit microscopic descriptions. In particular in this paper we show that there is just one Weyl orbit of A_r subalgebras for r < 6$. The orbit of the previously found A_2 solutions, together with space--brane representatives contains a pure metric representative that corresponds to homogeneous Bianchi type 2A cosmologies in D=4 based on the Heisenberg algebra. As a byproduct of our methods we obtain new exact solutions for such cosmologies with and without matter. We present a thorough investigation of their properties.

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arXiv2003

Potential and mass-matrix in gauged N=4 supergravity

We discuss the potential and mass-matrix of gauged N=4 matter coupled supergravity for the case of six matter multiplets, extending previous work by considering the dependence on all scalars. We consider all semi-simple gauge groups and analyse the potential and its first and second derivatives in the origin of the scalar manifold. Although we find in a number of cases an extremum with a positive cosmological constant, these are not stable under fluctuations of all scalar fields.

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arXiv2003

Unusual gauged supergravities from type IIA and type IIB orientifolds

We analyse different N=4 supergravities coupled to six vector multiplets corresponding to low-energy descriptions of the bulk sector of T6/Z2 orientifolds with p-brane in IIB (p odd) and in IIA (p even) superstrings. When fluxes are turned on, a gauging emerges corresponding to some non-semisimple Lie algebra related to nilpotent algebras N_p inside so(6,6), with dimension 15 + (p-3)(9-p). The non-metric axions have Stueckelberg couplings that induce a spontaneous breaking of gauge symmetries. In four cases the gauge algebra is non-abelian with a non-commutative structure of the compactification torus, due to fluxes of NS-NS and R-R forms.

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arXiv2003

New D=4 gauged supergravities from N=4 orientifolds with fluxes

We consider classes of T_6 orientifolds, where the orientifold projection contains an inversion I_{9-p} on 9-p coordinates, transverse to a Dp-brane. In absence of fluxes, the massless sector of these models corresponds to diverse forms of N=4 supergravity, with six bulk vector multiplets coupled to N=4 Yang--Mills theory on the branes. They all differ in the choice of the duality symmetry corresponding to different embeddings of SU(1,1)\times SO(6,6+n) in Sp(24+2n,R), the latter being the full group of duality rotations. Hence, these Lagrangians are not related by local field redefinitions. When fluxes are turned on one can construct new gaugings of N=4 supergravity, where the twelve bulk vectors gauge some nilpotent algebra which, in turn, depends on the choice of fluxes.

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arXiv2001

Supersymmetric 3-branes on smooth ALE manifolds with flux

We construct a new family of classical BPS solutions of type IIB supergravity describing 3-branes transverse to a 6-dimensional space with topology R^2*ALE. They are characterized by a non-trivial flux of the supergravity 2-forms through the homology 2-cycles of a generic smooth ALE manifold. Our solutions have two Killing spinors and thus preserve N=2 supersymmetry. They are expressed in terms of a quasi harmonic function H (the ``warp factor''), whose properties we study in the case of the simplest ALE, namely the Eguchi-Hanson manifold. The equation for H is identified as an instance of the confluent Heun equation. We write explicit power series solutions and solve the recurrence relation for the coefficients, discussing also the relevant asymptotic expansions. While, as in all such N=2 solutions, supergravity breaks down near the brane, the smoothing out of the vacuum geometry has the effect that the warp factor is regular in a region near the cycle. We interpret the behavior of the warp factor as describing a three-brane charge ``smeared'' over the cycle and consider the asymptotic form of the geometry in that region, showing that conformal invariance is broken even when the complex type IIB 3-form field strength is assumed to vanish. We conclude with a discussion of the basic features of the gauge theory dual.

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arXiv2000

How much can supergravity teach us about microscopic features of BPS black holes?

We review recent results in the study of regular four dimensional BPS black holes in toroidally compactified type II (or M) theory. We discuss the generating solution for this kind of black holes, its microscopic description(s), and compute the corresponding microscopic entropy. These achievements, which provide a description of the fundamental degrees of freedom accounting for the entropy of any regular BPS black hole in the theory under consideration, are inscribed within a research project aimed to the study of the microscopic properties of this kind of solutions in relation to U--duality invariants computed on the corresponding macroscopic (supergravity) description.

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arXiv2000

Microscopic entropy of the most general four-dimensional BPS black hole

In a recent paper we have given the macroscopic and microscopic description of the generating solution of toroidally compactified string theory BPS black holes. In this note we compute its corresponding microscopic entropy. Since by definition the generating solution is the most general solution modulo U-duality transformations, this result allows for a description of the fundamental degrees of freedom accounting for the entropy of any regular BPS black holes of toroidally compactified string (or M) theory.

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arXiv2000

Regular BPS black holes: macroscopic and microscopic description of the generating solution

In this paper we construct the BPS black hole generating solution of toroidally compactified string (and M) theory, giving for it both the macroscopic and microscopic description. Choosing a proper U-duality gauge the latter will be given by a bound state made solely of D-branes. The axionic nature of the supergravity solution will be directly related to non-trivial angles between the constituent D-branes (type IIB configuration) or, in a T-dual gauge, to the presence of magnetic flux on constituent D-brane world volumes (type IIA configuration). As expected, the four dimensional axion fields arise from the dimensional reduction of non-diagonal metric tensor components or Kalb-Ramond B field components for type IIB or type IIA cases, respectively. Thanks to this result it is then now possible to fill the full 56-dimensional U-duality orbit of N=8 BPS black holes and to have a macroscopic and microscopic description of all of them.

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arXiv2000

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.

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arXiv1999

The generating solution of regular N=8 BPS black holes

In this paper we construct the 5 parameter generating solution of N=8 BPS regular supergravity black holes as a five parameter solution of the N=2 STU model. Our solution has a simpler form with respect to previous constructions already appeared in the literature and moreover, through the embedding [SL(2)]^3\subset SU(3,3)\subset E_{(7)7} discussed in previous papers, the action of the U-duality group is well defined. This allows to reproduce via U-duality rotations any other solution, like those corresponding to R-R black holes whose microscopic description is given by intersecting D-branes.

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arXiv1999

N=8 BPS black holes preserving 1/8 supersymmetry

In the context of N=8 supergravity we consider BPS black-holes that preserve 1/8 supersymmetry. It was shown in a previous paper that, modulo U-duality transformations of E_{7(7)} the most general solution of this type can be reduced to a black-hole of the STU model. In this paper we analize this solution in detail, considering in particular its embedding in one of the possible Special Kähler manifold compatible with the consistent truncations to N=2 supergravity, this manifold being the moduli space of the T^6/Z^3 orbifold, that is: SU(3,3)/SU(3)*U(3). This construction requires a crucial use of the Solvable Lie Algebra formalism. Once the group-theoretical analisys is done, starting from a static, spherically symmetric ansätz, we find an exact solution for all the scalars (both dilaton and axion-like) and for gauge fields, together with their already known charge-dependent fixed values, which yield a U-duality invariant entropy. We give also a complete translation dictionary between the Solvable Lie Algebra and the Special Kähler formalisms in order to let comparison with other papers on similar issues being more immediate. Although the explicit solution is given in a simplified case where the equations turn out to be more manageable, it encodes all the features of the more general one, namely it has non-vanishing entropy and the scalar fields have a non-trivial radial dependence.

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