Angelo Galante

Deformed special relativity as an effective theory of measurements on quantum gravitational backgrounds

In this article we elaborate on a recently proposed interpretation of deformed special relativity (DSR) as an effective measurement theory in the presence of non-negligible (albeit small) quantum gravitational fluctuations. We provide several heuristic arguments to explain how such a new theory can emerge and discuss the possible observational consequences of this framework. Given that our discussion considers leading order corrections to the standard dispersion relations, our results apply to a very wide class of possible modifications of special relativity.

Targeting CXCR1 on breast cancer stem cells: signaling pathways and clinical application modelling

In breast cancer it has been proposed that the presence of cancer stem cells may drive tumor initiation, progression and recurrences. IL-8, up-regulated in breast cancer, and associated with poor prognosis, increases CSC self-renewal in cell line models. It signals via two cell surface receptors, CXCR1 and CXCR2. Recently, the IL-8/CXCR1 axis was proposed as an attractive pathway for the design of specific therapies against breast cancer stem cells. Reparixin, a powerful CXCR1 inhibitor, was effective in reducing in vivo the tumour-initiating population in several NOD/SCID mice breast cancer models, showing that the selective targeting of CXCR1 and the combination of reparixin and docetaxel resulted in a concomitant reduction of the bulk tumour mass and CSC population. The available data indicate that IL-8, expressed by tumour cells and induced by chemotherapeutic treatment, is a key regulator of the survival and self-renewal of the population of CXCR1-expressing CSC. Consequently, this investigation on the mechanism of action of the reparixin/paclitaxel combination, was based on the observation that reparixin treatment contained the formation of metastases in several experimental models. However, specific data on the formation of breast cancer brain metastases, which carry remarkable morbidity and mortality to a substantial proportion of advanced breast cancer patients, have not been generated. The obtained data indicate a beneficial use of the drug combination reparixin and paclitaxel to counteract brain tumour metastasis due to CSC, probably due to the combined effects of the two drugs, the pro-apoptotic action of paclitaxel and the cytostatic and anti-migratory effects of reparixin.

Space–time fluctuations and ultra-high energy cosmic ray interactions

Abstract The intimate geometry of space–time is expected to suffer stochastic fluctuations as a result of quantum gravitational effects. These fluctuations may induce observable consequences on the propagation of high energy particles over large distances, so that the strength and the characteristics of these fluctuations may be constrained, mainly in the range of energies of interest for cosmic ray physics. While invoked as a possible explanation for the detection of the puzzling cosmic rays with energies in excess of the threshold for photopion production (the so-called super-Greisen–Zatsepin–Kuzmin particles), we demonstrate here that lower energy observations may provide strong constraints on the role of a fluctuating space–time structure.

Finite density QCD: a new approach

We introduce a new approach to analyze the phase diagram of QCD at finite chemical potential and temperature, test it in the Gross-Neveu model at finite baryon density, and apply it to the study of the chemical potential-temperature phase diagram of QCD with four degenerate flavors of Kogut-Susskind type.

Modified special relativity on a fluctuating spacetime

It was recently proposed that deformations of the relativistic symmetry, as those considered in deformed special relativity (DSR), can be seen as the outcome of a measurement theory in the presence of non-negligible (albeit small) quantum gravitational fluctuations [S. Liberati, S. Sonego, and M. Visser, Phys. Rev. D 71, 045001 (2005).][R. Aloisio, A. Galante, A. Grillo, S. Liberati, E. Luzio, and F. Mendez, Phys. Rev. D 73, 045020 (2006).]. In this paper we explicitly consider the case of a spacetime described by a flat metric endowed with stochastic fluctuations and, for a free particle, we show that DSR-like nonlinear relations between the spaces of the measured and classical momenta, can result from the average of the stochastic fluctuations over a scale set to be the de Broglie wavelength of the particle. As illustrative examples we consider explicitly the averaging procedure for some simple stochastic processes and discuss the physical implications of our results.

Phase diagram of QCD with four quark flavors at finite temperature and baryon density

Abstract We analyze the phase diagram of QCD with four staggered flavors in the ( μ , T ) plane using a method recently proposed by us. We explore the region T ≳ 0.7 T C and μ ≲ 1.4 T C , where T C is the transition temperature at zero baryon density, and find a first order transition line. Our results are quantitatively compatible with those obtained with the imaginary chemical potential approach and the double reweighting method, in the region where these approaches are reliable, T ≳ 0.9 T C and μ ≲ T C . But, in addition, our method allows us to extend the transition line to lower temperatures and higher chemical potentials.

Particle and antiparticle sectors in DSR1 and κ-Minkowski space-time

In this paper we explore the problem of antiparticles in DSR1 and κ-Minkowski space-time following three different approaches inspired by the Lorentz invariant case: (a) the dispersion relation, (b) the Dirac equation in space-time and (c) the Dirac equation in momentum space. We find that it is possible to define a map Sdsr which gives the antiparticle sector from the negative frequency solutions of the wave equation. In κ-Poincare, the corresponding map Skp is the antipodal mapping, which is different from Sdsr. The difference is related to the composition law, which is crucial to define the multiparticle sector of the theory. This discussion permits to show that the energy of the antiparticle in DSR is the positive root of the dispersion relation, which is consistent with phenomenological approaches.

Approaching space-time through velocity in doubly special relativity

We discuss the definition of velocity as

Diquark condensation at strong coupling

dE/d|mathbf{p}|

Critical behavior of CP(1) at theta=pi, Haldane's conjecture, and the relevant universality class.

, where