Daniele Binosi

The Pinch technique to all orders

A generalization of the pinch technique to all orders in perturbation theory is presented. The effective Greens functions constructed with this procedure are singled out in a unique way through the full exploitation of the underlying Becchi-Rouet-Stora-Tyutin symmetry. A simple all-order correspondence between the pinch technique and the background field method in the Feynman gauge is established.

Spatial soliton formation in photonic crystal fibers.

We demonstrate the existence of spatial soliton solutions in photonic crystal fibers (PCFs). These guided localized nonlinear waves appear as a result of the balance between the linear and nonlinear diffraction properties of the inhomogeneous photonic crystal cladding. The spatial soliton is realized self-consistently as the fundamental mode of the effective fiber defined simultaneously by the PCF linear and the self-induced nonlinear refractive indices. It is also shown that the photonic crystal cladding is able to stabilize these solutions, which would be unstable otherwise if the medium was entirely homogeneous.

Vortex solitons in photonic crystal fibers.

We demonstrate the existence of vortex soliton solutions in photonic crystal fibers. We analyze the role played by the photonic crystal fiber defect in the generation of optical vortices. An analytical prediction for the angular dependence of the amplitude and phase of the vortex solution based on group theory is also provided. Furthermore, all the analysis is performed in the non-paraxial regime.

Pinch technique and the Batalin-Vilkovisky formalism

In this paper we take the first step towards a non-diagrammatic formulation of the Pinch Technique. In particular we proceed into a systematic identification of the parts of the one-loop and two-loop Feynman diagrams that are exchanged during the pinching process in terms of unphysical ghost Greens functions; the latter appear in the standard Slavnov-Taylor identity satisfied by the tree-level and one-loop three-gluon vertex. This identification allows for the consistent generalization of the intrinsic pinch technique to two loops, through the collective treatment of entire sets of diagrams, instead of the laborious algebraic manipulation of individual graphs, and sets up the stage for the generalization of the method to all orders. We show that the task of comparing the effective Greens functions obtained by the Pinch Technique with those computed in the background field method Feynman gauge is significantly facilitated when employing the powerful quantization framework of Batalin and Vilkovisky. This formalism allows for the derivation of a set of useful non-linear identities, which express the Background Field Method Greens functions in terms of the conventional (quantum) ones and auxiliary Greens functions involving the background source and the gluonic anti-field; these latter Greens functions are subsequently related by means of a Schwinger-Dyson type of equation to the ghost Greens functions appearing in the aforementioned Slavnov-Taylor identity.

Pinch technique self-energies and vertices to all orders in perturbation theory

The all-order construction of the pinch technique gluon self-energy and quark?gluon vertex is presented in detail within the class of linear covariant gauges. The main ingredients in our analysis are the identification of a special Green function, which serves as a common kernel to all self-energy and vertex diagrams, and the judicious use of the Slavnov?Taylor identity it satisfies. In particular, it is shown that the ghost-Green functions appearing in this identity capture precisely the result of the pinching action at arbitrary order. By virtue of this observation the construction of the quark?gluon vertex becomes particularly compact. It turns out that the aforementioned ghost-Green functions play a crucial role, their net effect being the non-trivial modification of the ghost diagrams of the quark?gluon vertex in such a way as to reproduce dynamically the characteristic ghost sector of the background field method. The gluon self-energy is also constructed following two different procedures. First, an indirect derivation is given, by resorting to the strong induction method and the assumption of the uniqueness of the S-matrix. Second, an explicit construction based on the intrinsic pinch technique is provided, using the Slavnov?Taylor identity satisfied by the all-order three-gluon vertex nested inside the self-energy diagrams. The process independence of the gluon self-energy is also demonstrated, by using gluons instead of quarks as external test particles, and identifying the corresponding kernel function, together with its Slavnov?Taylor identity. Finally, the general methodology for carrying out the renormalization of the resulting Green functions is outlined, and various open questions are briefly discussed.

Domain wall junctions in a generalized Wess-Zumino model.

Abstract We investigate domain wall junctions in a generalized Wess-Zumino model with a Z N symmetry. We present a method to identify the junctions that are potentially BPS saturated. We then use a numerical simulation to show that those junctions indeed saturate the BPS bound for N=4. In addition, we study the decay of unstable non-BPS junctions.

Domain walls in supersymmetric QCD: The taming of the zoo

We provide a unified picture of the domain wall spectrum in supersymmetric QCD with

Forward-backward equations for nonlinear propagation in axially invariant optical systems.

{N}_{c}

CP violation through particle mixing and the H-A lineshape

colors and

Gauge-independent off-shell fermion self-energies at two loops: The cases of QED and QCD

{N}_{f}