arXiv subjects
Publications and source records attributed to R. Marotta.
In the framework of Type IIB String Theory compactified on a general six-torus T6 with arbitrary complex structure, Yukawa couplings are determined for the chiral matter described by open strings ending on D9-branes having different oblique magnetization.
In the framework of low-energy effective actions of branes compactified on magnetized extra-dimensions, we determine Yukawa couplings for the chiral matter described by open strings attached to D9 branes having different oblique magnetization and living on a general torus T6 with an arbitrary complex structure. These results generalize the ones existing in literature.
We construct the six-dimensional Lagrangian for the massless twisted open strings with one end-point ending on a stack of D5 and the other on a stack of D9 branes, interacting with the gauge multiplets living respectively on the D5 and D9 branes. It is first obtained by uplifting to six dimensions the four-dimensional Lagrangian of the N=2 hypermultiplet and manifestly exhibits an SU(2) symmetry. We show by an explicit calculation that it is N=1 supersymmetric in six dimensions and then we check various terms of this Lagrangian by computing string amplitudes on the disk. Finally, starting from this Lagrangian and assuming the presence of non-zero magnetic fluxes along the extra compact dimensions, we determine the spectrum of the Kaluza-Klein states which agrees with the corresponding one obtained from string theory in the field theory limit.
We use both a string and a field theoretical approach in order to determine respectively the Kaehler metrics of untwisted and twisted open strings attached to magnetized D9 branes in toroidal compactifications.
Using the field theoretical approach introduced by Cremades, Ibanez and Marchesano for describing open strings attached to D9 branes having different magnetizations, we give a procedure for determining the Kaehler metrics of those open strings in toroidal compactifications.
We discuss two inequivalent ways for describing magnetized D-branes wrapped N times on a torus T^2. The first one is based on a non-abelian gauge bundle U(N), while the second one is obtained by means of a Narain T-duality transformation acting on a theory with non-magnetized branes. We construct in both descriptions the boundary state and the open string vertices and show that they give rise to different string amplitudes. In particular, the description based on the gauge bundle has open string vertex operators with momentum dependent Chan-Paton factors.
We review the string construction of the ``orientifold field theories'' and we show that for these theories the gauge/gravity correspondence is only valid for a large number of colours.
In this paper we consider the gauge theory living on the world-volume of a stack of N D3-branes of Type 0B/Ω' I_6(-1)^{F_{L}} and of its orbifolds C^2/Z_2 and C^3/(Z_2 x Z_2). The gauge theories obtained in the three cases are a brane realization of ``orientifold field theories'' having the bosonic sector common with N=4,2,1 super Yang-Mills respectively. In these non-supersymmetric theories, we investigate the possibility of keeping the gauge/gravity correspondence that has revealed itself so successful in the case of supersymmetric theories. In the open string framework we compute the coefficient of the gauge kinetic term showing that the perturbative behaviour of the orientifold field theory can be obtained from the closed string channel in the large N limit, where the theory exhibits Bose-Fermi degeneracy.
We discuss the role played by the divergences appearing in the interaction between a fractional D3 brane dressed with an SU(N) gauge field and a stack of N fractional D3 branes on the orbifolds C^2/Z_2 and C^3/(Z_2 x Z_2). In particular we show that the logarithmic divergences in the closed string channel, interpreted as due to twisted massless tadpoles, are mapped, under open/closed string duality, in the logarithmic ones in the open string channel, due to the massless states circulating in the annulus diagram and corresponding to the one-loop divergences that one finds in the gauge theory living in the world volume of the brane. This result provides a quantitative evidence of why the chiral and scale anomalies of the supersymmetric and non conformal gauge theories supported by the world volume of the branes can be inferred from supergravity calculations.
We compute the annulus diagram corresponding to the interaction of a fractional D3 brane with a gauge field on its world-volume and a stack of N fractional D3 branes on the orbifolds C^2 /Z_2 and C^3/Z_2 x Z_2. We show that its logarithmic divergence can be equivalently understood as due either to massless open string states circulating in the loop or to massless closed string states exchanged between two boundary states. This follows from the fact that, under open/closed string duality, massless states in the open and closed string channels are matched into each other without mixing with massive states. This explains why the perturbative properties of many gauge theories living on the worldvolume of less supersymmetric and nonconformal branes have been recently obtained from their corresponding supergravity solution.
We study a bound state of fractional D3-branes localized inside the world-volume of fractional D7-branes on the orbifold C^3/Z_2 x Z_2. We determine the open string spectrum that leads to N=1 U(N1)xU(N2)xU(N3)xU(N4) gauge theory with matter having the number of D7-branes as a flavor index. We derive the linearized boundary action of the D7-brane on this orbifold using the boundary state formalism and we discuss the tadpole cancellation. After computing the asymptotic expression of the supergravity solution the anomalies of the gauge theory are reproduced.
In this note we show how the anomalies of both pure and matter coupled N=1,2 supersymmetric gauge theories describing the low energy dynamics of fractional branes on orbifolds can be derived from supergravity.
We discuss fractional D3-branes on the orbifold C^3/Z_2*Z_2. We study the open and the closed string spectrum on this orbifold. The corresponding N=1 theory on the brane has, generically, a U(N_1)*U(N_2)*U(N_3)*U(N_4) gauge group with matter in the bifundamental. In particular, when only one type of brane is present, one obtains pure N=1 Yang-Mills. We study the coupling of the branes to the bulk fields and present the corresponding supergravity solution, valid at large distances. By using a probe analysis, we are able to obtain the Wilsonian beta-function for those gauge theories that possess some chiral multiplet. Although, due to the lack of moduli, the probe technique is not directly applicable to the case of pure N=1 Yang-Mills, we point out that the same formula gives the correct result also for this case.
This is a pedagogical and extended version of the results published in Refs. [1,2] and presented by the authors in various talks during the last year. We discuss the type II D-branes (both regular and fractional) of the orbifold R^{1,5}*R^4/Z_2, we determine their corresponding supergravity solution and show how this can be used to study the properties of N=2 super Yang-Mills. Supergravity is able to reproduce the perturbative moduli space of the gauge theory, while it does not encode the non-perturbative corrections. The short distance region of space-time, which corresponds to the infrared region of the gauge theory, is excised by an enhancon mechanism, and more states should be included in the low energy effective action in order to enter inside the enhancon and recover the instanton corrections. (To be published on a Memorial Volume commemorating Michael Marinov)
We study a bound state of fractional D3/D7-branes in the ten-dimensional space R^{1,5}*R^{4}/Z_2 using the boundary state formalism. We construct the boundary actions for this system and show that higher order terms in the twisted fields are needed in order to satisfy the zero-force condition. We then find the classical background associated to the bound state and show that the gauge theory living on a probe fractional D3-brane correctly reproduces the perturbative behavior of a four-dimensional N=2 supersymmetric gauge theory with fundamental matter.
We study the classical geometry associated to fractional D3-branes of type IIB string theory on R^4/Z_2 which provide the gravitational dual for N=2 super Yang-Mills theory in four dimensions. As one can expect from the lack of conformal invariance on the gauge theory side, the gravitational background displays a repulson-like singularity. It turns out however, that such singularity can be excised by an enhancon mechanism. The complete knowledge of the classical supergravity solution allows us to identify the coupling constant of the dual gauge theory in terms of the string parameters and to find a logarithmic running that is governed precisely by the beta-function of the N=2 super Yang-Mills theory.
We compute off-shell three- and four-tachyon amplitudes at tree level by using a prescription based on the requirement of projective invariance. In particular we show that the off-shell four-tachyon amplitude can be put in the same form as the corresponding on-shell one, exhibiting therefore the same analyticity properties. This is shown both for the bosonic and the fermionic string. The result obtained in the latter case can be extended to the off-shell four-tachyon amplitude in type 0 theory.
We study the classical geometry produced by a stack of stable (i.e. tachyon free) non-BPS D-branes present in K3 compactifications of type II string theory. This classical representation is derived by solving the equations of motion describing the low-energy dynamics of the supergravity fields which couple to the non-BPS state. Differently from what expected, this configuration displays a singular behaviour: the space-time geometry has a repulson-like singularity. This fact suggests that the simplest setting, namely a set of coinciding non-interacting D-branes, is not acceptable. We finally discuss the possible existence of other acceptable configurations corresponding to more complicated bound states of these non-BPS branes.