arXiv subjects

L. Martucci

Publications and source records attributed to L. Martucci.

13 recordsLinked to original sources

arXiv2019

Higher Forms and Membranes in 4D Supergravities

We review the dynamical generation of coupling constants in 4D supergravity by means of gauge three-form fields. The latter are introduced as components of particular chiral supermultiplets and can be coupled to membranes preserving local supersymmetry. Such a set-up naturally arises from type-II string compactifications on Calabi-Yau manifolds with fluxes. We present generic 4D $\mathcal N=1$ supergravity models with three-form multiplets and study domain wall solutions supported by membranes, which interpolate between vacua with different values of the cosmological constant.

hep-th↗

arXiv2008

Warped generalized geometry compactifications, effective theories and non-perturbative effects

Summarizing the results of arXiv:0707.1038, we discuss the four-dimensional effective approach to type II N=1 supersymmetric flux compactifications with general SU(3)x SU(3)-structure. In particular, we study the effect of a non-trivial warp factor, which we argue leads naturally to a supergravity formulation invariant under local complexified Weyl transformations. We show that the full ten-dimensional supersymmetry equations can be obtained as F-flatness and D-flatness conditions from the superpotential and Kaehler potential. We then consider non-perturbative corrections to these supersymmetry conditions, following from adding instanton or gaugino condensation effects to the superpotential. As examples, we show how smeared instantons allow to understand the ten-dimensional geometry of KKLT-like AdS vacua and we give an explanation for the superpotential for "mobile" D3-branes in terms of a non-perturbatively induced generalized complex structure.

hep-th↗

arXiv2007

Heavy hadron spectra from spin chains and strings

We study the spectrum of hadronic states made up of very massive complex scalar fields in a confining gauge theory admitting a supergravity dual background. We show that for a sub-sector of operators dual to certain spinning strings, the mass spectrum exhibits an integrable structure equal to the Heisenberg spin chain, up to an overall factor. This result is compared with the corresponding string prediction.

hep-th↗

arXiv2007

Splitting of macroscopic fundamental strings in flat space and holographic hadron decays

In this review article we present the calculation of the splitting rate in flat space of a macroscopic fundamental string either intersecting at a generic angle a Dp-brane or lying on it. The result is then applied, in the context of the string/gauge theory correspondence, to the study of exclusive decay rates of large spin mesons into mesons. As examples, we discuss the cases of N=4 SYM with a small number of flavors, and of QCD-like theories in the quenched approximation. In the latter context, explicit analytic formulas are given for decay rates of mesons formed either by heavy quarks or by massless quarks.

hep-th↗

arXiv2006

Meson decays from string splitting

We discuss exclusive decays of large spin mesons into mesons in models of large N_c quenched QCD at strong coupling using string theory. The rate of the processes are calculated by studying the splitting of a macroscopic string on the relevant dual gravity backgrounds. We study analytic formulas for the decay rates of mesons made up of very heavy or very light quarks.

hep-th↗

arXiv2006

String splitting and strong coupling meson decay

We study the decay of high spin mesons using the gauge/string theory correspondence. The rate of the process is calculated by studying the splitting of a macroscopic string intersecting a D-brane. The result is applied to the decay of mesons in N=4 SYM with a small number of flavors and in a gravity dual of large N QCD. In QCD the decay of high spin mesons is found to be heavily suppressed in the regime of validity of the supergravity description.

hep-th↗

arXiv2004

Semiclassical spinning strings and confining gauge theories

We study multi-charged rotating string states on Type IIB regular backgrounds dual to confining SU(N) gauge theories with (softly broken) {\cal N}=1 supersymmetry, in the infra red regime. After exhibiting the classical energy/charge relations for the folded and circular two-charge strings, we compute in the latter case the one loop sigma-model quantum correction. The classical relation has an expansion in positive powers of the analogous of the BMN effective coupling, while the quantum corrections are non perturbative in nature and are not subleading in the limit of infinite charge. We comment about the dual field theory multi-charged hadrons and the implications of our computation for the AdS/{\cal N}=4 duality.

hep-th↗

arXiv2004

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.

hep-th↗

arXiv2002

Noncommutative Electrodynamics

In this paper we define a causal Lorentz covariant noncommutative (NC) classical Electrodynamics. We obtain an explicit realization of the NC theory by solving perturbatively the Seiberg-Witten map. The action is polynomial in the field strenght $F$, allowing to preserve both causality and Lorentz covariance. The general structure of the Lagrangian is studied, to all orders in the perturbative expansion in the NC parameter $θ$. We show that monochromatic plane waves are solutions of the equations of motion to all orders. An iterative method has been developed to solve the equations of motion and has been applied to the study of the corrections to the superposition law and to the Coulomb law.

hep-th↗

arXiv2002

Noncommutative Einstein-AdS Gravity in three Dimensions

We present a Lorentzian version of three-dimensional noncommutative Einstein-AdS gravity by making use of the Chern-Simons formulation of pure gravity in 2+1 dimensions. The deformed action contains a real, symmetric metric and a real, antisymmetric tensor that vanishes in the commutative limit. These fields are coupled to two abelian gauge fields. We find that this theory of gravity is invariant under a class of transformations that reduce to standard diffeomorphisms once the noncommutativity parameter is set to zero.

hep-th↗

arXiv2002

Noncommutative Gravity in two Dimensions

We deform two-dimensional topological gravity by making use of its gauge theory formulation. The obtained noncommutative gravity model is shown to be invariant under a class of transformations that reduce to standard diffeomorphisms once the noncommutativity parameter is set to zero. Some solutions of the deformed model, like fuzzy AdS_2, are obtained. Furthermore, the transformation properties of the model under the Seiberg-Witten map are studied.

hep-th↗

arXiv2002

Noncommutative AdS Supergravity in three Dimensions

In this paper we propose a generalization of N=4 three dimensional AdS supergravity to the noncommutative case. This is a supersymmetric version of the results presented in hep-th/0201103. We show that it continues to admit an N=4 supersymmetric solution which is the noncommutative couterpart of AdS_3 space. Some other solutions are also discussed.

hep-th↗

arXiv2001

Dirac's Observables for the Rest-Frame Instant Form of Tetrad Gravity in a Completely Fixed 3-Orthogonal Gauge

We define the {\it rest-frame instant form} of tetrad gravity restricted to Christodoulou-Klainermann spacetimes. After a study of the Hamiltonian group of gauge transformations generated by the 14 first class constraints of the theory, we define and solve the multitemporal equations associated with the rotation and space diffeomorphism constraints, finding how the cotriads and their momenta depend on the corresponding gauge variables. This allows to find quasi-Shanmugadhasan canonical transformation to the class of 3-orthogonal gauges and to find the Dirac observables for superspace in these gauges. The construction of the explicit form of the transformation and of the solution of the rotation and supermomentum constraints is reduced to solve a system of elliptic linear and quasi-linear partial differential equations. We then show that the superhamiltonian constraint becomes the Lichnerowicz equation for the conformal factor of the 3-metric and that the last gauge variable is the momentum conjugated to the conformal factor. The gauge transformations generated by the superhamiltonian constraint perform the transitions among the allowed foliations of spacetime, so that the theory is independent from its 3+1 splittings. In the special 3-orthogonal gauge defined by the vanishing of the conformal factor momentum we determine the final Dirac observables for the gravitational field even if we are not able to solve the Lichnerowicz equation. The final Hamiltonian is the weak ADM energy restricted to this completely fixed gauge.

gr-qc↗