arXiv subjects

S. Bellucci

Publications and source records attributed to S. Bellucci.

174 records · Page 10Linked to original sources

arXiv1996

The W(sl(N+3),sl(3)) algebras and their contractions to W3

We construct the nonlinear $W(sl(N+3),sl(3))$ algebras and find the spectrum of values of the central charge that gives rise, by contracting the $W(sl(N+3),sl(3))$ algebras, to a $W_3$ algebra belonging to the coset $W((sl(N+3),sl(3))/(u(1)\oplus sl(N))$. Part of the spectrum was conjectured before, but part of it is given here for the first time. Using the tool of embedding the $W(sl(N+3),sl(3))$ algebras into linearizing algebras, we construct new realizations of $W_3$ modulo null fields. The possibility to predict, within the conformal linearization framework, the central charge spectrum for minimal models of the nonlinear $W(sl(N+3),sl(3))$ algebras is discussed at the end.

hep-th↗

arXiv1996

Effects of the gravivector and graviscalar fields in N=2,8 supergravity

The available tests of the equivalence principle constrain the mass of the Higgs-like boson appearing in extended supergravity theories. We determine the constraints imposed by high precision experiments on the antigravity fields (gravivector and graviscalar) arising from $N=2,8$ supergravity.

hep-ph↗

arXiv1996

Physics Cahiers No. 1

We begin herewith the editing of physics notes taken in the course of Journal Club seminars at INFN-LNF in 1996. The activity consists of informal talks about work in progress and/or review of (more or less) recent physics results of interest to our laboratory. In the section titles the name of the speakers appear, together with the topics discussed in the seminars. We plan to publish these notes twice a year.

hep-ph↗

arXiv1995

Null Fields Realizations of $W_3$ from $W(sl(4),sl(3))$ and $W(sl(3|1),sl(3))$ Algebras

We consider the nonlinear algebras $W(sl(4),sl(3))$ and $W(sl(3|1),sl(3))$ and find their realizations in terms of currents spanning conformal linearizing algebras. The specific structure of these algebras, allows us to construct realizations modulo null fields of the $W_3$ algebra that lies in the cosets $W(sl(4),sl(3))/u(1)$ and $W(sl(3|1),sl(3))/u(1)$. Such realizations exist for the following values of the $W_3$ algebra central charge: $c_W=-30,-40/7,-98/5,-2$. The first two values are listed for the first time, whereas for the remaining values we get the new realizations in terms of an arbitrary stress tensor and $u(1)\times sl(2)$ affine currents.

hep-th↗

arXiv1995

Experimental limits on antigravity in extended supergravity

The available tests of the equivalence principle constrain the mass of the Higgs-like boson appearing in extended supergravity theories. We determine the constraints imposed by the present and future high precision experiments on the antigravity fields arising from $N=2,8$ supergravity.

hep-ph↗

arXiv1995

Pion (Kaon) and Sigma polarizabilities

We report the results of the working group on ``Pion (Kaon) and Sigma Polarizabilities''. Interesting possibilities to measure these polarizabilities include the radiative pion photoproduction in the MAMI experiment at Mainz, as well as at the GRAAL facility (actually the latter is being considered for an experimental determination of the pion polarizabilities here for the first time), the experimental plans on Primakoff effect at FNAL, and the measurements at the Frascati $Φ$-factory DA$Φ$NE.

hep-ph↗

arXiv1995

$γγ\to π^0 π^0$ and $η\to π^0 γγ$ at low energy within the Extended Nambu Jona-Lasinio Model

Within the Extended Nambu Jona-Lasinio model, we calculate the $O(p^6)$ counterterms entering the low-energy expansion of the $γγ\to π^0 π^0$ and the $η\to π^0 γγ$ amplitudes in Chiral Perturbation Theory. For $γγ\to π^0 π^0$ our results are compatible with both the experimental data and the two-loop calculation using meson resonance saturation. For the $η$ decay we find $Γ(η\toπ^0 γγ)=0.58\pm 0.3$ eV which is in agreement with experiment within one standard deviation. We also give predictions for the neutral pion polarizabilities and compare them with the results obtained from resonance saturation.

hep-ph↗

arXiv1994

Linearizing $W_{2,4}$ and $WB_2$ Algebras

It has recently been shown that the $W_3$ and $W_3^{(2)}$ algebras can be considered as subalgebras in some linear conformal algebras. In this paper we show that the nonlinear algebras $W_{2,4}$ and $WB_2$ as well as Zamolodchikov's spin $5/2$ superalgebra also can be embedded as subalgebras into some linear conformal algebras with a finite set of currents. These linear algebras give rise to new realizations of the nonlinear algebras which could be suitable in the construction of $W$-string theories.

hep-th↗

arXiv1994

Nonlinear Realizations of the $W_3^{(2)}$ Algebra

In this letter we consider the nonlinear realizations of the classical Polyakov's algebra $W_3^{(2)}$. The coset space method and the covariant reduction procedure allow us to deduce the Boussinesq equation with interchanged space and evolution coordinates. By adding one more space coordinate and introducing two copies of the $W_3^{(2)}$ algebra, the same method yields the $sl(3,R)$ Toda lattice equations.

hep-th↗

arXiv1994

Low-Energy Photon-Photon Collisions to Two-Loop Order

We evaluate the amplitude for $γγ\rightarrow π^0 π^0$ to two loops in chiral perturbation theory. The three new counterterms which enter at this order in the low-energy expansion are estimated with resonance saturation. We find that the cross section agrees rather well with the available data and with dispersion theoretic calculations even substantially above threshold. Numerical results for the Compton cross section and for the neutral pion polarizabilities are also given to two-loop accuracy.

hep-ph↗

arXiv1993

N=2 Super Boussinesq Hierarchy: Lax Pairs and Conservation Laws

We study the integrability properties of the one-parameter family of $N=2$ super Boussinesq equations obtained earlier by two of us (E.I. \& S.K., Phys. Lett. B 291 (1992) 63) as a hamiltonian flow on the $N=2$ super-$W_3$ algebra. We show that it admits nontrivial higher order conserved quantities and hence gives rise to integrable hierarchies only for three values of the involved parameter, $α=-2,\;-1/2,\;5/2$. We find that for the case $α= -1/2$ there exists a Lax pair formulation in terms of local $N=2$ pseudo-differential operators, while for $α= -2$ the associated equation turns out to be bi-hamiltonian.

hep-th↗

arXiv1992

N=3 Supersymmetric Extension of KdV Equation

We construct a one-parameter family of N=3 supersymmetric extensions of the KdV equation as a Hamiltonian flow on N=3 superconformal algebra and argue that it is non-integrable for any choice of the parameter. Then we propose a modified N=3 super KdV equation which possesses the higher order conserved quantities and so is a candidate for an integrable system. Upon reduction to N=2, it yields the recently discussed ``would-be integrable'' version of the N=2 super KdV equation. In the bosonic core it contains a coupled system of the KdV type equation and a three-component generalization of the mKdV equation. We give a Hamiltonian formulation of the new N=3 super KdV equation as a flow on some contraction of the direct sum of two N=3 superconformal algebras.

hep-th↗