Gauge and Poincare' Invariant Regularization and Hopf Symmetries

We consider the regularization of a gauge quantum field theory following a modification of the Polchinski proof based on the introduction of a cutoff function. We work with a Poincare' invariant deformation of the ordinary point-wise product of fields introduced by Ardalan, Arfaei, Ghasemkhani and Sadooghi, and show that it yields, through a limiting procedure of the cutoff functions, to a regularized theory, preserving all symmetries at every stage. The new gauge symmetry yields a new Hopf algebra with deformed co-structures, which is inequivalent to the standard one.Comment: Revised version. 14 pages. Incorrect statements eliminate

Decoherent Scattering of Light Particles in a D-Brane Background

We discuss the scattering of two light particles in a D-brane background. It is known that, if one light particle strikes the D brane at small impact parameter, quantum recoil effects induce entanglement entropy in both the excited D brane and the scattered particle. In this paper we compute the asymptotic `out' state of a second light particle scattering off the D brane at large impact parameter, showing that it also becomes mixed as a consequence of quantum D-brane recoil effects. We interpret this as a non-factorizing contribution to the superscattering operator S-dollar for the two light particles in a Liouville D-brane background, that appears when quantum D-brane excitations are taken into account.Comment: 18 pages LATEX, one figure (incorporated

Twisting all the way: from Classical Mechanics to Quantum Fields

We discuss the effects that a noncommutative geometry induced by a Drinfeld twist has on physical theories. We systematically deform all products and symmetries of the theory. We discuss noncommutative classical mechanics, in particular its deformed Poisson bracket and hence time evolution and symmetries. The twisting is then extended to classical fields, and then to the main interest of this work: quantum fields. This leads to a geometric formulation of quantization on noncommutative spacetime, i.e. we establish a noncommutative correspondence principle from *-Poisson brackets to *-commutators. In particular commutation relations among creation and annihilation operators are deduced.Comment: 32 pages. Added references and details in the introduction and in Section

Confinement in Gauge Theories from the Condensation of World-Sheet Defects in Liouville String

We present a Liouville-string approach to confinement in four-dimensional gauge theories, which extends previous approaches to include non-conformal theories. We consider Liouville field theory on world sheets whose boundaries are the Wilson loops of gauge theory, which exhibit vortex and spike defects. We show that world-sheet vortex condensation occurs when the Wilson loop is embedded in four target space-time dimensions, and show that this corresponds to the condensation of gauge magnetic monopoles in target space. We also show that vortex condensation generates a effective string tension corresponding to the confinement of electric degrees of freedom. The tension is independent of the string length in a gauge theory whose electric coupling varies logarithmically with the length scale. The Liouville field is naturally interpreted as an extra target dimension, with an anti-de-Sitter (AdS) structure induced by recoil effects on the gauge monopoles, interpreted as D branes of the effective string theory. Black holes in the bulk AdS space correspond to world-sheet defects, so that phases of the bulk gravitational system correspond to the different world-sheet phases, and hence to different phases of the four-dimensional gauge theory. Deconfinement is associated with a Berezinskii-Kosterlitz-Thouless transition of vortices on the Wilson-loop world sheet, corresponding in turn to a phase transition of the black holes in the bulk AdS space.Comment: 29 pages LATEX, three eps figures incorporate

Lorentz-violation and cosmological perturbations: a toy brane-world model

We study possible effects of Lorentz-violation on the generation of cosmological perturbations at inflation by introducing a simple inflating five-dimensional brane-world setup with violation of four-dimensional Lorentz-invariance at an energy scale $k$. We consider massless scalar field, meant to mimic perturbations of inflaton and/or gravitational field, in this background. At three-momenta below $k$, there exists a zero mode localized on the brane, whose behaviour coincides with that in four-dimensional theory. On the contrary, at three-momenta above $k$, the localized mode is absent and physics is entirely five-dimensional. As three-momenta get redshifted, more modes get localized on the brane, the phenomenon analogous to ``mode generation''. We find that for $k\gg H$, where $H$ is the inflationary Hubble scale, the spectrum of perturbations coincides with that in four-dimensional theory. For $k < H$ and time-dependent bulk parameters, the spectrum deviates, possibly strongly, from the flat spectrum even for pure de Sitter inflation.Comment: 5 figures, iopart, minor changes, appendix adde

How emergency surgery has changed during the COVID-19 pandemic: A cohort study

Introduction: Various surgical societies constantly update their recommendations in order to adapt surgical activity on current Pandemic conditions. The aim of this study is to analyze how hospitalizations and emergency operations have changed in our Department of Medical and Surgical Sciences in the Hospital of Foggia during covid-19 pandemic. Methods: Our cohort-study was conducted by analyzing two groups of patients admitted to the Department of Medical and Surgical Sciences of the Hospital of Foggia: those admitted during the no-covid period from March 09th, 2019 to May 09th, 2019 and those during the covid period from March 09th, 2020 to May 09th, 2020. Results: A total of 750 patients admitted during the no-covid period of 2019 and 171 during the covid period of 2020, of these 222 were emergency admission during 2019 and 97 during 2020, 528 were elective admission during 2019 and 74 during 2020. Of the emergency admissions (222 during 2019 and 97 during 2020), 91 were operated during the no covid period in 2019 and 52 during the covid period in 2020. The mean Mannheim Peritonitis Index Score, that is a scoring system used in peritonitis which is simple and cost-effective, were 15.6 during the no covid period of 2019 and 22.2 during the covid period of 2020. We observed 29 post-operative complications during 2019 and 26 during 2020. Conclusions: Contraction of admissions for urgent and emergent conditions in the first period of lockdown has been followed from some positive effects as well as aggravating consequences

Cosmological Perturbations in Non-Commutative Inflation

We compute the spectrum of cosmological perturbations in a scenario in which inflation is driven by radiation in a non-commutative space-time. In this scenario, the non-commutativity of space and time leads to a modified dispersion relation for radiation with two branches, which allows for inflation. The initial conditions for the cosmological fluctuations are thermal. This is to be contrasted with the situation in models of inflation in which the accelerated expansion of space is driven by the potential energy of a scalar field, and in which the fluctuations are of quantum vacuum type. We find that, in the limit that the expansion of space is almost exponential, the spectrum of fluctuations is scale-invariant with a slight red tilt. The magnitude of the tilt is different from what is obtained in a usual inflationary model with the same expansion rate during the period of inflation. The amplitude also differs, and can easily be adjusted to agree with observations.Comment: 7 pages, 1 figur

Astrophysical Probes of the Constancy of the Velocity of Light

We discuss possible tests of the constancy of the velocity of light using distant astrophysical sources such as gamma-ray bursters (GRBs), Active Galactic Nuclei (AGNs) and pulsars. This speculative quest may be motivated by some models of quantum fluctuations in the space-time background, and we discuss explicitly how an energy-dependent variation in photon velocity \delta c/ c \sim - E / M arises in one particular quantum-gravitational model. We then discuss how data on GRBs may be used to set limits on variations in the velocity of light, which we illustrate using BATSE and OSSE observations of the GRBs that have recently been identified optically and for which precise redshifts are available. We show how a regression analysis can be performed to look for an energy-dependent effect that should correlate with redshift. The present data yield a limit M \gsim 10^{15} GeV for the quantum gravity scale. We discuss the prospects for improving this analysis using future data, and how one might hope to distinguish any positive signal from astrophysical effects associated with the sources.Comment: 37 pages LaTeX, 9 eps figures included, uses aasms4.st

A general condition of inflationary cosmology on trans-Planckian physics

We consider a more general initial condition satisfying the minimal uncertainty relationship. We calculate the power spectrum of a simple model in inflationary cosmology. The results depend on perturbations generated below a fundamental scale, e.g. the Planck scale.Comment: 7 pages, References adde

Relativistic quantum model of confinement and the current quark masses

We consider a relativistic quantum model of confined massive spinning quarks and antiquarks which describes leading Regge trajectories of mesons. The quarks are described by the Dirac equations and the gluon contribution is approximated by the Nambu-Goto straight-line string. The string tension and the current quark masses are the main parameters of the model. Additional parameters are phenomenological constants which approximate nonstring short-range contributions. Comparison of the measured meson masses with the model predictions allows one to determine the current quark masses (in MeV) to be $m_s = 227 \pm 5,~ m_c = 1440 \pm 10,~ m_b = 4715 \pm 20$. The chiral $SU_3$ model[23] makes it possible to estimate from here the $u$- and $d$-quark masses to be $m_u = 6.2 \pm 0.2$~ Mev and $m_d = 11.1 \pm 0.4$ Mev.Comment: 15 pages, LATEX, 2 tables. (submitted to Phys.Rev.D