Black holes production in self-complete quantum gravity

A regular black hole model, which has been proposed by Hayward, is reconsidered in the framework of higher dimensional TeV unification and self-complete quantum gravity scenario (Dvali, Spallucci). We point out the "quantum" nature of these objects and compute their cross section production by taking into account the key role played by the existence of a "minimal length" l_0. We show as the threshold energy is related to l_0. We recover, in the high energy limit, the standard "black-disk" form of the cross section, while it vanishes, below threshold, faster than any power of the invariant mass-energy \sqrt{-s}.Comment: 12 pages; 3 figures; accepted for publication in PL

Un-spectral dimension and quantum spacetime phases

In this Letter, we propose a new scenario emerging from the conjectured presence of a minimal length $\ell$ in the spacetime fabric, on the one side, and the existence of a new scale invariant, continuous mass spectrum, of un-particles on the other side. We introduce the concept of \textit{un-spectral dimension} $\mathbb{D}_U$ of a $d$-dimensional, euclidean (quantum) spacetime, as the spectral dimension measured by an "un-particle" probe. We find a general expression for the un-spectral dimension $\mathbb{D}_U$ labelling different spacetime phases: a semi-classical phase, where ordinary spectral dimension gets contribution from the scaling dimension $d_U$ of the un-particle probe ; a critical "Planckian phase", where four-dimensional spacetime can be effectively considered two-dimensional when $d_U=1$; a "Trans-Planckian phase", which is accessible to un-particle probes only, where spacetime as we currently understand it looses its physical meaning.Comment: 5 pages, 1 figure, version matching that published by Physics Letters

Thermodynamical phases of a regular SAdS black hole

This paper studies the thermodynamical stability of regular BHs in AdS5 background. We investigate off-shell free energy of the system as a function of temperature for different values of a "coupling constant" L=4 theta/l^2, where the cosmological constant is Lambda = -3/l^2 and \sqrt{theta} is a "minimal length". The parameter L admits a critical value, L_{inf}=0.2, corresponding to the appearance of an inflexion point in the Hawking temperature. In the weak-coupling regime L < L_{inf}, there are first order phase transitions at different temperatures. Unlike the Hawking-Page case, at temperature 0\le T \le T_{min} the ground state is populated by "cold" near-extremal BHs instead of a pure radiation. On the other hand, for L \g L_{inf} only large, thermodynamically stable, BHs exist.Comment: 12 pages; 6 Figures; accepted for publication in Int. J. Mod. Phys.

Zero-point length, extra-dimensions and string T-duality

In this paper, we are going to put in a single consistent framework apparently unrelated pieces of information, i.e. zero-point length, extra-dimensions, string T-duality. More in details we are going to introduce a modified Kaluza-Klein theory interpolating between (high-energy) string theory and (low-energy) quantum field theory. In our model zero-point length is a four dimensional ``virtual memory'' of compact extra-dimensions length scale. Such a scale turns out to be determined by T-duality inherited from the underlying fundamental string theory. From a low energy perspective short distance infinities are cut off by a minimal length which is proportional to the square root of the string slope, i.e. \sqrt{\alpha^\prime}. Thus, we provide a ``bridge'' between the ultra-relativistic string domain and the low energy arena of point-particle quantum field theory.Comment: 28 pages, Latex, no figures; two references adde

The Abelian Higgs model and a minimal length in an un-particle scenario

We consider both the Abelian Higgs model and the impact of a minimal length in the un-particle sector. It is shown that even if the Higgs field takes a non-vanishing v.e.v., gauge interaction keeps its long range character leading to an effective gauge symmetry restoration. The effect of a quantum gravity induced minimal length on a physical observable is then estimated by using a physically-based alternative to the usual Wilson loop approach. Interestingly, we obtain an ultraviolet finite interaction energy described by a confluent hyper-geometric function, which shows a remarkable richness of behavior.Comment: 6 pages. Tp appear in EP

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.Comment: 4 page