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Euro Spallucci

Publications and source records attributed to Euro Spallucci.

At least 55 records · Page 3Linked to original sources

Some aspects of a Chern-Simons-like coupling in an external magnetic field

For a gauge theory which includes a light massive vector field interacting with the familiar photon U(1)_{QED} via a Chern-Simons- like coupling, we study the static quantum potential. Our analysis is based on the gauge-invariant, but path-dependent, variables formalism. The result is that the theory describes an exactly screening phase. Interestingly enough, this result displays a marked departure of a qualitative nature from the axionic elctrodynamics result. However, the present result is analogous to that encountered in the coupling between the familiar photon U(1)_{QED} and a second massive gauge field living in the so-called hidden-sector U(1)_h, inside a superconducting box.

hep-th↗

"Kerrr" black hole: the Lord of the String

Kerrr in the title is not a typo. The third "r" stands for "regular", in the sense of pathology-free, rotating black hole. We exhibit a long search-for, exact, Kerr-like, solution of the Einstein equations with novel features: i) no curvature ring singularity; ii) no "anti-gravity" universe with causality violating timelike closed world-lines; iii) no "super-luminal" matter disk. The ring singularity is replaced by a classical, circular, rotating string with Planck tension representing the inner engine driving the rotation of all the surrounding matter. The resulting geometry is regular and smoothly interpolates among inner Minkowski space, borderline deSitter and outer Kerr universe. The key ingredient to cure all unphysical features of the ordinary Kerr black hole is the choice of a "noncommutative geometry inspired" matter source as the input for the Einstein equations, in analogy with spherically symmetric black holes described in earlier works.

hep-th↗

Noncommutative geometry inspired dirty black holes

We provide a new exact solution of the Einstein equations which generalizes the noncommutative geometry inspired Schwarzschild metric, we previously obtained. We consider here more general relations between the energy density and the radial pressure and find new a geometry describing a regular ``dirty black hole''. We discuss strong and weak energy condition violations and various aspects of the regular dirty black hole thermodynamics.

gr-qc↗

From screening to confinement in a Higgs-like model

We investigate a recently proposed Higgs-like model (arXiv:0811.4423 [hep-th]), in the framework of a gauge-invariant but path-dependent variables formalism. We compute the static potential between test charges in a condensate of scalars and fermions. In the case of charged massive scalar we recover the screening potential. On the other hand, in the Higgs case, with a "tachyonic" mass term and a quartic potential in the Lagrangian, unexpected features are found. It is observed that the interaction energy is the sum of an effective-Yukawa and a linear potential, leading to the confinement of static charges.

hep-th↗

Non-commutative geometry inspired higher-dimensional charged, black holes

We obtain a new, exact, solution of the Einstein's equation in higher dimensions. The source is given by a static spherically symmetric, Gaussian distribution of mass and charge. De-localization of mass and charge is due to the presence of a "minimal length" in the spacetime fabric, coming from quantum gravitational effects, e.g. string induced non-commutative geometry. The resulting metric describes a regular, i.e. curvature singularity free, charged black hole in higher dimensions. The metric smoothly interpolates between Reissner-Nordstrom geometry at large distance, and deSitter spacetime at short distance. Thermodynamical properties of the black hole are investigated and the form of the Area Law is determined. We show that back reaction effects are negligible even near the temperature maximum for any reasonable number of extra dimensions. We study pair creation and show that the upper bound on the discharge time increases with the number of extra dimensions.

hep-th↗

A note on unparticle in lower dimensions

Using the gauge-invariant but path-dependent variables formalism, we examine the effect of the space-time dimensionality on a physical observable in the unparticle scenario. We explicitly show that long-range forces between particles mediated by unparticles are still present whenever we go over into lower dimensions.

hep-th↗

Remarks on confinement driven by axion-like particles in Yang-Mills theories

Features of screening and confinement are studied for a non-Abelian gauge theory with a mixture of pseudoscalar and scalar coupling, in the case where a constant chromo-electric, or chromo-magnetic, strength expectation value is present. Our discussion is carried out using the gauge-invariant but path-dependent variables formalism. We explicitly show that the static potential profile is the sum of a Yukawa and a linear potential, leading to the confinement of static probe charges. Interestingly, similar results have been obtained in the context of gluodynamics in curved space-time. For only pseudoscalar coupling, the results are radically different.

hep-th↗

Un-particle Effective Action

We study un-particle dynamics in the framework of standard quantum field theory. We obtain the Feynman propagator by supplementing standard quantum field theory definitions with integration over the mass spectrum. Then we use this information to construct effective actions for scalar, gauge vector and gravitational un-particles.

hep-th↗

Confinement from gluodynamics in curved space-time

We determine the static potential for a heavy quark-antiquark pair from gluodynamics in curved space-time. Our calculation is done within the framework of the gauge-invariant, path-dependent, variables formalism. The potential energy is the sum of a Yukawa and a linear potential, leading to the confinement of static charges.

hep-th↗

Static potential from spontaneous breaking of scale symmetry

We determine the static potential for a heavy quark-antiquark pair from the spontaneous symmetry breaking of scale invariance in a non-Abelian gauge theory. Our calculation is done within the framework of the gauge-invariant, path-dependent, variables formalism. The result satisfies the 't Hooft basic criterion for achieving confinement.

hep-th↗

Noncommutative geometry inspired charged black holes

We find a new, non-commutative geometry inspired, solution of the coupled Einstein-Maxwell field equations describing a variety of charged, self-gravitating objects, including extremal and non-extremal black holes. The metric smoothly interpolates between deSitter geometry, at short distance, and Reissner-Nordstroem geometry far away from the origin. Contrary to the ordinary Reissner-Nordstroem spacetime there is no curvature singularity in the origin neither "naked" nor shielded by horizons. We investigate both the Hawking process and pair creation in this new scenario.

gr-qc↗

Confinement from constant field condensates

For a $(2+1)$-dimensional reformulated SU(2) Yang-Mills theory, we compute the interaction potential within the framework of the gauge-invariant but path-dependent variables formalism. This reformulation is due to the presence of a constant gauge field condensate. Our results show that the interaction energy contains a linear term leading to the confinement of static probe charges. This result is equivalent to that of the massive Schwinger model.

hep-th↗

Confinement effects from interacting chromo-magnetic and axion fields

We study a non-Abelian gauge theory with a pseudo scalar coupling ϕε^{μναβ} F_{μν}^a F_{αβ}^a in the case where a constant chromo-electric, or chromo-magnetic, strength expectation value is present. We compute the interaction potential within the framework of gauge-invariant, path-dependent, variables formalism. While in the case of a constant chromo-electric field strength expectation value the static potential remains Coulombic, in the case of a constant chromo-magnetic field strength the potential energy is the sum of a Coulombic and a linear potentials, leading to the confinement of static charges.

hep-th↗

Trace Anomaly in Quantum Spacetime Manifold

In this paper we investigate the trace anomaly in a spacetime where single events are de-localized as a consequence of short distance quantum coordinate fluctuations. We obtain a modified form of heat kernel asymptotic expansion which does not suffer from short distance divergences. Calculation of the trace anomaly is performed using an IR regulator in order to circumvent the absence of UV infinities. The explicit form of the trace anomaly is presented and the corresponding 2D Polyakov effective action and energy momentumtensor are obtained. The vacuum expectation value of the energy momentum tensor in the Boulware, Hartle-Hawking and Unruh vacua is explicitly calculated in a (rt)-section of a recently found, noncommutative geometry inspired, Schwarzschild-like solution of the Einstein equations. The standard short distance divergences in the vacuum expectation values are regularized in agreement with the absence of UV infinities removed by quantum coordinate fluctuations.

hep-th↗

TeV Mini Black Hole Decay at Future Colliders

It is generally believed that mini black holes decay by emitting elementary particles with a black body energy spectrum. The original calculation lead to the conclusion that about the 90% of the black hole mass is radiated away in the form of photons, neutrinos and light leptons, mainly electrons and muons. With the advent of String Theory, such a scenario must be updated by including new effects coming from the stringy nature of particles and interactions.By taking for granted that black holes can be produced in hadronic collisions, then their decay must take into account that: (i) we live in a D3-Brane embedded into an higher dimensional bulk spacetime; (ii) fundamental interactions, including gravity, are unified at TeV energy scale. Thus, the formal description of the Hawking radiation mechanism has to be extended to the case of more than four spacetime dimensions and include the presence of D-branes. Furthermore, unification of fundamental interactions at an energy scale many order of magnitude lower than the Planck energy implies that any kind of fundamental particle, not only leptons, is expected to be emitted. A detailed understanding of the new scenario is instrumental for optimal tuning of detectors at future colliders, where, hopefully, this exciting new physics will be tested. In this article we review higher dimensional black hole decay, considering not only the emission of particles according to Hawking mechanism, but also their near horizon QED/QCD interactions. The ultimate motivation is to build up a phenomenologically reliable scenario, allowing a clear experimental signature of the event.

hep-ph↗

Noncommutative geometry inspired Schwarzschild black hole

We investigate the behavior of a noncommutative radiating Schwarzschild black hole. It is shown that coordinate noncommutativity cures usual problems encountered in the description of the terminal phase of black hole evaporation. More in detail, we find that: the evaporation end-point is a zero temperature extremal black hole even in the case of electrically neutral, non-rotating, objects; there exists a finite maximum temperature that the black hole can reach before cooling down to absolute zero; there is no curvature singularity at the origin, rather we obtain a regular DeSitter core at short distance.

gr-qc↗

The role of a dynamical measure and dynamical tension in brane creation and growth

The use of a non-Riemannian measure of integration in the action of strings and branes allows the possibility of dynamical tension. In particular, lower dimensional objects living in the string/brane can induce discontinuities in the tension: the effect of pair creation on the string tension is studied. We investigate then the role that these new features can play in string and brane creation and growth. A mechanism is studied by means of which a scalar field can transfer its energy to the tension of strings and branes. An infinite dimensional symmetry group of this theory is discussed. Creation and growth of bubbles in a formulation that requires mass generation for the bulk gauge fields coupled to the branes is also discussed.

hep-th↗

The fate of radiating black holes in noncommutative geometry

We investigate the behavior of a radiating Schwarzschild black hole toy-model in a 2D noncommutative spacetime. It is shown that coordinate noncommutativity leads to: i) the existence of a minimal non-zero mass to which black hole can shrink; ii) a finite maximum temperature that the black hole can reach before cooling down to absolute zero; iii) the absence of any curvature singularity. The proposed scenario offers a possible solution to conventional difficulties when describing terminal phase of black hole evaporation.

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