Searcharxiv⌕ Search

arXiv subjects

Mario Tonin

Publications and source records attributed to Mario Tonin.

At least 19 recordsLinked to original sources
arXiv2016

Brane induced supersymmetry breaking and de Sitter supergravity

We obtain a four-dimensional supergravity with spontaneously broken supersymmetry allowing for de Sitter vacua by coupling a superspace action of minimal N=1, D=4 supergravity to a locally supersymmetric generalization of the Volkov-Akulov goldstino action describing the dynamics of a space-filling non-BPS 3-brane in N=1, D=4 superspace. To the quadratic order in the goldstino field the obtained action coincides with earlier constructions of supergravities with nilpotent superfields, while matching the higher-order contributions will require a non-linear redefinition of fields. In the unitary gauge, in which the goldstino field is set to zero, the action coincides with that of Volkov and Soroka. We also show how a nilpotency constraint on a chiral curvature superfield emerges in this formulation.

hep-th↗
arXiv2014

High-Q silicon photonic crystal cavity for enhanced optical nonlinearities

We fabricate and experimentally characterize a $H0$ photonic crystal slab nanocavity with a design optimized for maximal quality factor, $Q = 1.7$ million. The cavity, fabricated from a silicon slab, has a resonant mode at $λ= 1.59 \mathrm{μm}$ and a measured $Q$-factor of $400,000$. It displays nonlinear effects, including high-contrast optical bistability, at a threshold power among the lowest ever reported for a silicon device. With a theoretical modal volume as small as $V = 0.34(λ/n)^3$, this cavity ranks among those with the highest $Q/V$ ratios ever demonstrated, while having a small footprint suited for integration in photonic circuits.

physics.optics↗
arXiv2013

On Semiclassical Equivalence of Green-Schwarz and Pure Spinor Strings in AdS(5) x S(5)

We present a method to study the equivalence at the semiclassical level of the Green-Schwarz and pure spinor formulations of String Theory in AdS(5) x S(5). This method provides a clear separation of the physical and unphysical sectors of the pure spinor formulation and allows one to prove that the two models have not only equal spectra for the fermionic fluctuations but also equal conformal weights (the bosonic ones being equal by construction).

hep-th↗
arXiv2012

Covariant actions for models with non-linear twisted self-duality

We describe a systematic way of the generalization, to models with non-linear duality, of the space-time covariant and duality-invariant formulation of duality-symmetric theories in which the covariance of the action is ensured by the presence of a single auxiliary scalar field. It is shown that the duality-symmetric action should be invariant under the two local symmetries characteristic of this approach, which impose constraints on the form of the action similar to those of Gaillard and Zumino and in the non-covariant formalism. We show that the (twisted) self-duality condition obtained from this action upon integrating its equations of motion can always be recast in a manifestly covariant form which is independent of the auxiliary scalar and thus corresponds to the conventional on-shell duality-symmetric covariant description of the same model. Supersymmetrization of this construction is briefly discussed.

hep-th↗
arXiv2011

Free Differential Algebras and Pure Spinor Action in IIB Superstring Sigma Models

In this paper we extend to the case of IIB superstring sigma models the method proposed in hep-th/10023500 to derive the pure spinor approach for type IIA sigma models. In particular, starting from the (Free) Differential Algebra and superspace parametrization of type IIB supergravity, extended to include the BRST differential and all the ghosts, we derive the BRST transformations of fields and ghosts as well as the standard pure spinor constraints for the ghosts $λ$ related to supersymmetry. Moreover, using the method first proposed by us, we derive the pure spinor action for type IIB superstrings in curved supergravity backgrounds (on shell), in full agreement with the action first obtained by Berkovits and Howe.

hep-th↗
arXiv2010

Pure Spinor Approach to Type IIA Superstring Sigma Models and Free Differential Algebras

This paper considers the Free Differential Algebra and rheonomic parametrization of type IIA Supergravity, extended to include the BRS differential and the ghosts. We consider not only the ghosts lambda's of supersymmetry but also the ghosts corresponding to gauge and Lorentz transformations. In this way we can derive not only the BRS transformations of fields and ghosts but also the standard pure spinor constraints on lambda's. Moreover the formalism allows to derive the action for the pure spinor formulation of type IIA superstrings in a general background, recovering the action first obtained by Berkovits and Howe.

hep-th↗
arXiv2009

BLG-motivated Lagrangian formulation for the chiral two-form gauge field in D=6 and M5-branes

We reveal non-manifest gauge and SO(1,5) Lorentz symmetries in the Lagrangian description of a six-dimensional free chiral field derived from the Bagger-Lambert-Gustavsson model in arXiv:0804.3629 and make this formulation covariant with the use of a triplet of auxiliary scalar fields. We consider the coupling of this self-dual construction to gravity and its supersymmetrization. In the case of the non-linear model of arXiv:0805.2898 we solve the equations of motion of the gauge field, prove that its non-linear field strength is self-dual and find a gauge-covariant form of the non-linear action. Issues of the relation of this model to the known formulations of the M5-brane worldvolume theory are discussed.

hep-th↗
arXiv2008

Superspace formulations of ten-dimensional supergravity

We present a new formulation for N=1, D=10 supergravity in superspace, in presence of a Lorentz Chern-Simons-form. This formulation entails the following properties: it furnishes a solution of the Bianchi identities that is algebraically consistent to all orders in alpha'; at first order it is the simplest formulation proposed so far, and it is therefore most suitable for an explicit higher order analysis; it allows a well defined perturbative expansion in alpha', in which no poltergeist fields appear; it reconciles the two different classes of first order solutions available in the literature, that until now appeared physically inequivalent.

hep-th↗
arXiv2008

Y-Formalism and Curved Beta-Gamma Systems

We adopt the Y-formalism to study beta-gamma systems on hypersurfaces. We compute the operator product expansions of gauge-invariant currents and we discuss some applications of the Y-formalism to model on Calabi-Yau spaces.

hep-th↗
arXiv2007

Y-formalism and $b$ ghost in the Non-minimal Pure Spinor Formalism of Superstrings

We present the Y-formalism for the non-minimal pure spinor quantization of superstrings. In the framework of this formalism we compute, at the quantum level, the explicit form of the compound operators involved in the construction of the $b$ ghost, their normal-ordering contributions and the relevant relations among them. We use these results to construct the quantum-mechanical $b$ ghost in the non-minimal pure spinor formalism. Moreover we show that this non-minimal $b$ ghost is cohomologically equivalent to the non-covariant $b$ ghost.

hep-th↗
arXiv2005

The b-Field in Pure Spinor Quantization of Superstrings

In the framework of the pure spinor approach of superstring theories, we describe the Y-formalism and use it to compute the picture raised b-field. At the end we discuss briefly the new, non-minimal formalism of Berkovits and the related non-minimal b-field.

hep-th↗
arXiv2005

Worldline Approach of Topological BF Theory

We present a worldline description of topological non-abelian BF theory in arbitrary space-time dimensions. It is shown that starting with a trivial classical action defined on the worldline, the BRST cohomology has a natural representation as the sum of the de Rham cohomology. Based on this observation, we construct a second-quantized action of the BF theory. Interestingly enough, this theory naturally gives us a minimal solution to the Batalin-Vilkovisky master equation of the BF theory. Our formalism sheds some light not only on an interplay between the Witten-type and the Schwarz-type topological quantum field theories but also on the role of the Batalin-Vilkovisky antifields and ghosts as geometrical and elementary objects.

hep-th↗
arXiv2004

Superfield Theories in Tensorial Superspaces and the Dynamics of Higher Spin Fields

We present the superfield generalization of free higher spin equations in tensorial superspaces and analyze tensorial supergravities with GL(n) and SL(n) holonomy as a possible framework for the construction of a non-linear higher spin field theory. Surprisingly enough, we find that the most general solution of the supergravity constraints is given by a class of superconformally flat and OSp(1|n)-related geometries. Because of the conformal symmetry of the supergravity constraints and of the higher spin field equations such geometries turn out to be trivial in the sense that they cannot generate a `minimal' coupling of higher spin fields to their potentials even in curved backgrounds with a non-zero cosmological constant. This suggests that the construction of interacting higher spin theories in this framework might require an extension of the tensorial superspace with additional coordinates such as twistor-like spinor variables which are used to construct the OSp(1|2n) invariant (`preonic') superparticle action in tensorial superspace.

hep-th↗
arXiv2004

On the b-antighost in the Pure Spinor Quantization of Superstrings

Recently Berkovits has constructed a picture raised, compound field $b_B$ which is used to compute higher loop amplitudes in the pure spinor approach of superstrings. On the other hand, in the twisted and gauge fixed, superembedding approach with $n=2$ world-sheet (w.s.) supersymmetry that reproduces the pure spinor formulation, a field $b$ appears quite naturally as the current of one of the two twisted charges of the w.s. supersymmetry, the other being the BRST charge. In this paper we study the relation between $b$ and $b_B$. We shall show that $bZ$, where $Z$ is a picture raising operator, and $b_B$ belong to the same BRST cohomological class. This result is of importance since it implies that the cumbersome singularity which is present in $b$, is in fact harmless if $b$ is combined with $Z$.

hep-th↗
arXiv2002

The Superembedding Origin of the Berkovits Pure Spinor Covariant Quantization of Superstrings

We show that the pure spinor formalism proposed by Berkovits to covariantly quantize superstrings is a gauge fixed, twisted version of the complexified n=2 superembedding formulation of the superstring. This provides the Berkovits approach with a geometrical superdiffeomorphism invariant ground. As a consequence, the absence of the worldsheet (super)diffeomorphism ghosts in the pure spinor quantization prescription and the nature of the Berkovits BRST charge and antighost are clarified. Since superembedding is classically equivalent to the Green-Schwarz formulation, we thus also relate the latter to the pure spinor construction.

hep-th↗
arXiv2001

On the Berkovits Covariant Quantization of GS Superstring

We study the covariant quantization of the Green-Schwarz (GS) superstrings proposed recently by Berkovits. In particular, we reformulate the Berkovits approach in a way that clarifies its relation with the GS approach and allows to derive in a straightforward way its extension to curved spacetime background. We explain the procedure working explicitly in the case of the heterotic string.

hep-th↗