Self sustained traversable wormholes and the equation of state

We compute the graviton one loop contribution to a classical energy in a \textit{traversable} wormhole background. The form of the shape function considered is obtained by the equation of state $p=\omega\rho$. We investigate the size of the wormhole as a function of the parameter $\omega$. The investigation is evaluated by means of a variational approach with Gaussian trial wave functionals. A zeta function regularization is involved to handle with divergences. A renormalization procedure is introduced and the finite one loop energy is considered as a \textit{self-consistent} source for the traversable wormhole.The case of the phantom region is briefly discussed.Comment: Uses RevTeX 4. 21 pages. Submitted to Classical and Quantum Gravity. Extended version of the talk given at ERE2006 (Palma de Mallorca, September 4-8, 2006) and of the talk given at MG11-GT5, Berlin, 23-29 July, 200

Spacetime Foam Model of the Schwarzschild Horizon

We consider a spacetime foam model of the Schwarzschild horizon, where the horizon consists of Planck size black holes. According to our model the entropy of the Schwarzschild black hole is proportional to the area of its event horizon. It is possible to express geometrical arguments to the effect that the constant of proportionality is, in natural units, equal to one quarter.Comment: 16 pages, 2 figures, improved and extended version with some significant changes. Accepted for publication in Phys.Rev.

Evaluation of the Casimir Force for a Dielectric-diamagnetic Cylinder with Light Velocity Conservation Condition and the Analogue of Sellmeir's Dispersion Law

We study the Casimir pressure for a dielectric-diamagnetic cylinder subject to light velocity conservation and with a dispersion law analogous to Sellmeir's rule. Similarities to and differences from the spherical case are pointed out.Comment: 19 pages Latex, no figures; discussion expanded. To appear in Physica Script

What to do in an oncology department to face the new COVID-19 era challenges?

9noItaly was the first European country to be hit by COVID-19 pandemic. As a consequence, Italian oncologists had to guarantee essential treatments although minimizing exposure to the virus, and accidental infection, of patients and healthcare professionals. As Department of Medical Oncology of the University Hospital of Udine, in this short report, we describe the measures that we have taken, and gradually updated, since February 26, 2020. All accesses to our Oncology facilities are currently regulated by entrance check-points where patients are screened for infections following dedicated algorithms. Up to date, after 6 weeks of systematic execution of swabs no physician, nurse or other individual of the staff has been found positive to COVID-19. Only one patient admitted for therapy has been identified as COVID-19 positive. The aim of our work is to propose a model, made up of a set of operative procedures, that may be adopted by all the oncologists that daily struggle to guarantee safety and care in Oncology during this COVID-19 emergency.openopenGarattini S.K.; Bin A.; Donato R.; Mansutti M.; Rizzato S.; Troiero G.; Candoni A.; Fanin R.; Fasola G.Garattini, S. K.; Bin, A.; Donato, R.; Mansutti, M.; Rizzato, S.; Troiero, G.; Candoni, A.; Fanin, R.; Fasola, G

Casimir effect in a wormhole spacetime

We consider the Casimir effect for quantized massive scalar field with non-conformal coupling $\xi$ in a spacetime of wormhole whose throat is rounded by a spherical shell. In the framework of zeta-regularization approach we calculate a zero point energy of scalar field. We found that depending on values of coupling $\xi$, a mass of field $m$, and/or the throat's radius $a$ the Casimir force may be both attractive and repulsive, and even equals to zero.Comment: 2 figures, 10 pages, added 2 reference

Rare and Insidious Toxicities from New Combination Therapies in Metastatic Renal Cell Cancer: Lessons Learned from Real-Practice

The advent of immune checkpoint inhibitors in combination with multitarget tyrosine kinase inhibitors has become a standard first-line treatment for metastatic renal cell cancer. Along with survival improvement, new toxicities have emerged. Such adverse events are still complex to be managed and some of them are rare and could be insidious or even fatal. Medical oncologists dispose of guidelines about the management of toxicities from immune checkpoint inhibitors but not for combinations. Therefore, it is still difficult to properly attribute and manage additive or overlapping adverse events. We report two clinical cases regarding rare treatment-related endocrine toxicities—hypophysitis and thyroiditis—with particular focus on their management. To this purpose, immune checkpoint-related toxicities guidelines represent the starting point. However, their implementation with additional measures is needed, considering the increasing complexity of current clinical scenarios. The goal is to correctly recognize adverse events and address side effects, so as not to discontinue effective treatments. We, therefore, aim at discussing the points of proper management of toxicities and individuating potential areas of improvement

Radial stability analysis of the continuous pressure gravastar

Radial stability of the continuous pressure gravastar is studied using the conventional Chandrasekhar method. The equation of state for the static gravastar solutions is derived and Einstein equations for small perturbations around the equilibrium are solved as an eigenvalue problem for radial pulsations. Within the model there exist a set of parameters leading to a stable fundamental mode, thus proving radial stability of the continuous pressure gravastar. It is also shown that the central energy density possesses an extremum in rho_c(R) curve which represents a splitting point between stable and unstable gravastar configurations. As such the rho_c(R) curve for the gravastar mimics the famous M(R) curve for a polytrope. Together with the former axial stability calculations this work completes the stability problem of the continuous pressure gravastar.Comment: 17 pages, 5 figures, References corrected, minor changes wrt v1, matches published versio

Linearized stability analysis of gravastars in noncommutative geometry

In this work, we find exact gravastar solutions in the context of noncommutative geometry, and explore their physical properties and characteristics. The energy density of these geometries is a smeared and particle-like gravitational source, where the mass is diffused throughout a region of linear dimension $\sqrt{(\alpha)}$ due to the intrinsic uncertainty encoded in the coordinate commutator. These solutions are then matched to an exterior Schwarzschild spacetime. We further explore the dynamical stability of the transition layer of these gravastars, for the specific case of $\beta=M^2/\alpha<1.9$, where M is the black hole mass, to linearized spherically symmetric radial perturbations about static equilibrium solutions. It is found that large stability regions exist and, in particular, located sufficiently close to where the event horizon is expected to form.Comment: 6 pages, 3 figure

Possible observation sequences of Brans-Dicke wormholes

The purpose of this study is to investigate observational features of Brans-Dicke wormholes in a case if they exist in our Universe. The energy flux from accretion onto a Brans-Dicke wormhole and the so-called "maximum impact parameter" are studied (the last one might allow to observe light sources through a wormhole throat). The computed values were compared with the corresponding ones for GR-wormholes and Schwarzschild black holes. We shown that Brans-Dicke wormholes are quasi-Schwarzschild objects and should differ from GR wormholes by about one order of magnitude in the accretion energy flux.Comment: 5 pages, 6 figure