arXiv subjects
Publications and source records attributed to P. Valtancoli.
We study the interconnection between the finite projective modules for a fuzzy sphere, determined in a previous paper, and the matrix model approach, making clear the physical meaning of noncommutative topological configurations.
We deconstruct the finite projective modules for the fuzzy four-sphere, described in a previous paper, and correlate them with the matrix model approach, making manifest the physical implications of noncommutative topology. We briefly discuss also the U(2) case, being a smooth deformation of the celebrated BPST SU(2) classical instantons on a sphere.
In this paper we shall investigate the possibility of solving U(1) theories on the non-commutative (NC) plane for arbitrary values of $θ$ by exploiting Morita equivalence. This duality maps the NC U(1) on the two-torus with a rational parameter $θ$ to the standard U(N) theory in the presence of a 't Hooft flux, whose solution is completely known. Thus, assuming a smooth dependence on $θ$, we are able to construct a series rational approximants of the original theory, which is finally reached by taking the large $N-$limit at fixed 't Hooft flux. As we shall see, this procedure hides some subletities since the approach of $N$ to infinity is linked to the shrinking of the commutative two-torus to zero-size. The volume of NC torus instead diverges and it provides a natural cut-off for some intermediate steps of our computation. In this limit, we shall compute both the partition function and the correlator of two Wilson lines. A remarkable fact is that the configurations, providing a finite action in this limit, are in correspondence with the non-commutative solitons (fluxons) found independently by Polychronakos and by Gross and Nekrasov, through a direct computation on the plane.
All fiber bundle with a given set of characteristic classes are viewable as particular projections of a more general bundle called a universal classifying space. This notion of projector valued field, a global definition of connections and gauge fields, can be useful to define vector bundles for non commutative base spaces. In this paper we derive the projector valued field for the fuzzy sphere, defining non-commutative n-monopole configurations, and check that in the classical limit, using the machinery of non-commutative geometry, the corresponding topological charges (Chern class) are integers.
We derive a first order formalism for solving the scattering of point sources in (2+1) gravity with negative cosmological constant. We show that their physical motion can be mapped, with a polydromic coordinate transformation, to a trivial motion, in such a way that the point sources move as time-like geodesics (in the case of particles) or as space-like geodesics (in the case of BTZ black holes) of a three-dimensional hypersurface immersed in a four-dimensional Minkowskian space-time, and that the two-body dynamics is solved by two invariant masses, whose difference is simply related to the total angular momentum of the system.
We propose an extension of a recent non-perturbative method suited for solving the N-body problem in (2+1)-gravity to the case of Chern-Simons supergravity. Coupling with supersymmetric point particles is obtained implicitly by extending the DJH matching conditions of gravity. The consistent solution of the interacting case is obtained by building a general non-trivial mapping, extending the superanalytic mapping, between a flat polydromic $X^M$ supercoordinate system and a physical one $x^N$, representing the DJH matching conditions around the superparticles. We show how to construct such a mapping in terms of analytic functions, and we give their exact expressions for the two body case. The extension to the N body case is also discussed. In the Minkoskian coordinates the superparticles move freely, and in particular the fermionic coordinates $Θ(ξ^N_{(i)})$ are constants, whose values can be fixed by using the monodromy properties. While the bosonic part of the supergeodesic equations are obtained, as in gravity, by measuring the bosonic distance in Minkowskian space-time, we find that the fermionic geodesic equations can be defined only by requiring that a non-perturbative divergence of the $X^M = X^M(x^N)$ mapping cancels out on the world-lines of the superparticles.
The complete, missing, Hamiltonian treatment of the standard SU(3)xSU(2)xU(1) model with Grassmann-valued fermion fields in the Higgs phase is given. We bypass the complications of the Hamiltonian theory in the Higgs phase, resulting from the spontaneous symmetry breaking with the Higgs mechanism, by studying the Hamiltonian formulation of the Higgs phase for the gauge equivalent Lagrangian in the unitary gauge. A canonical basis of Dirac's observables is found and the reduced physical Hamiltonian is evaluated. Its self-energy part is nonlocal for the electromagnetic and strong interactions, but local for the weak ones. Therefore, the Fermi 4-fermion interaction reappears at the nonperturbative level.
We derive a first-order formalism for solving $(2+1)$ gravity on Riemann surfaces, analogously to the recently discovered classical solutions for $N$ moving particles. We choose the York time gauge and the conformal gauge for the spatial metric. We show that Moncrief's equations of motion can be generally solved by the solution f of a $O(2,1$) sigma-model. We build out of f a mapping from a regular coordinate system to a Minkowskian multivalued coordinate system. The polydromy is in correspondence with the branch cuts on the complex plane representing the Riemann surface. The Poincaré holonomies, which define the coupling of Riemann surfaces to gravity, describe simply the Minkowskian free motion of the branch points. By solving f we can find the dynamics of the branch points in the physical coordinate system. We check this formalism in some cases, i.e. for the torus and for every Riemann surface with $SO(2,1)$ holonomies.
We derive, in 2+1 dimensions, classical solutions for metric and motion of two or more spinning particles, in the conformal Coulomb gauge introduced previously. The solutions are exact in the $N$-body static case, and are perturbative in the particles' velocities in the dynamic two-body case. A natural boundary for the existence of our gauge choice is provided by some ``CTC horizons'' encircling the particles, within which closed timelike curves occur.
We construct a non-perturbative, single-valued solution for the metric and the motion of $N$ interacting particles in $2+1$-Gravity. The solution is explicit for two particles with any speed and for any number of particles with small speed. It is based on a mapping from multivalued Minkowskian coordinates to single-valued ones, which solves the non-abelian monodromies due to particles' momenta. The two and three-body cases are treated in detail.
We construct a non-perturbative, single-valued solution for the metric and the motion of two interacting particles in ($2+1$)-Gravity, by using a Coulomb gauge of conformal type. The method provides the mapping from multivalued ( minkowskian ) coordinates to single-valued ones, which solves the non-abelian monodromies due to particles's momenta and can be applied also to the general N-body case.
By defining a regular gauge which is conformal-like and provides instantaneous field propagation, we investigate classical solutions of (2+1)-Gravity coupled to arbitrarily moving point-like particles. We show how to separate field equations from self-consistent motion and we provide a solution for the metric and the motion in the two-body case with arbitrary speed, up to second order in the mass parameters.