Very-High Energy Gamma Astrophysics

High-energy photons are a powerful probe for astrophysics and for fundamental physics under extreme conditions. During the recent years, our knowledge of the most violent phenomena in the Universe has impressively progressed thanks to the advent of new detectors for high-energy gamma-rays. Observation of gamma-rays gives an exciting view of the high-energy universe thanks to satellite-based telescopes (AGILE, GLAST) and to ground-based detectors like the Cherenkov telescopes (H.E.S.S. and MAGIC in particular), which recently discovered more than 60 new very-high-energy sources. The progress achieved with the last generation of Cherenkov telescopes is comparable to the one drawn by EGRET with respect to the previous gamma-ray satellite detectors. This article reviews the present status of high-energy gamma astrophysics, with emphasis on the recent results and on the experimental developments.Comment: 60 pages, 52 figures, (on line abstract replacement

\u201cThe Only Cure I Know Is a Good Ceremony": Post-traumatic Reconstruction of Identity in Leslie Marmon Silko\u2019s Ceremony

The article deals with the representation of post-traumatic stress disorder in Leslie Marmon Silko\u2019s novel Ceremony (1977), and with the complex psychological and cultural procedures of identity reconstruction its protagonist, half-blood Tayo, must follow in order to find some sort of inner balancing. Tayo\u2019s traumatic experience of war seems to schizophrenically split his identity, turning his \u201creal\u201d self into a Lacanian absence (the symptom of the \u201cReal\u201d), a void that denounces the source of the trauma (not the war in itself, which is mainly a metaphorical projection of Tayo\u2019s inner conflict, but his being neither Indian nor white) by erasing it from Tayo\u2019s consciousness and substituting it with a mythical plot that constructs him as a scapegoat-like figure responsible for the drought afflicting the Reservation. Both the novel and its main character at the end manage to reach some sort of coherence by accepting the unrepresentable Real and turning it upside down: they both finally reject the dream of a homogenous identity, and the trauma, no more something to be simply \u201ccured,\u201d is transformed into a source of self-definition, thanks to the equally polymorphic, hybrid, \u201cbroken\u201d ceremonies Tayo is subject to in the novel

"For the Bright Side of the Painting I Had a Limited Sympathy": Emancipation and Counter-Emancipation in Edgar Allan Poe's The Narrative of Arthur Gordon Pym

The article focuses on the contradictory construction of a free and self-reliant (and \u201cimperialist\u201d) white male identity in Edgar Allan Poe\u2019s The Narrative of Arthur Gordon Pym. Poe\u2019s romance builds up the myth of sea travelling as a way to reach an individual emancipation from the constraints (but also privileges) of social and familiar conditioning which ultimately fails due to a sort of \u201creturn of the repressed,\u201d of the censored reality that allows those same socio-familiar conditions to exist as they are \u2013 namely, the subjugation of black or non-white people who in the romance do not accept the role white domination would like to impose on them. On the other hand, the analogies linking Pym\u2019s predicament to the condition of African Americans in antebellum America (something symbolically alluded to in the famous quote \u201cFor the bright side of the painting I had a limited sympathy\u201d) threaten to subvert Poe\u2019s construction of a free and authorative white identity, undermined also by the sheer fact that at the end of the romance we have only one last man standing who knows the final outcome of the story \u2013 and this man is not Pym, but mixed-blood Dirk Peters, half white and half Indian, and showing some distinctly African American somatic features. The route of the American \u201cship\u201d comes therefore to ultimately look as already bound towards a dramatic redefinition of the power relationships between whites and non-whites, despite Pym\u2019s (and Poe\u2019s) desperate attempt to resist this change and reinstall individual and collective white authority

Evidence for an axion-like particle from blazar spectra?

Observations with the Imaging Atmospheric Cherenkov Telescopes H.E.S.S., MAGIC, CANGAROO III and VERITAS have shown that the Universe is more transparent than expected to gamma rays above 100GeV. As a natural explanation, the DARMA scenario has previously been proposed, wherein photons can oscillate into a new very light axionlike particle and vice-versa in the presence of cosmic magnetic fields. Here we demonstrate that the most recent observations further support the DARMA scenario, thereby making the existence of a very light axion-like particle more likely.Comment: 4 pages, 1 figure. Proceeding of the "6th Patras Workshop on Axions, WIMPs and WISPs", Zurich, Switzerland, 5 - 9 July 2010 (to appear in the Proceedings

Study of dynamical supersymmetry breaking for the two dimensional lattice Wess-Zumino model

A new approach to the study of the transition point in a class of two dimensional Wess-Zumino models is presented. The method is based on the calculation of rigorous lower bounds on the ground state energy density in the infinite lattice limit. Such bounds are useful in the discussion of supersymmetry phase transition. The transition point is then determined and compared with recent results based on large-scale Green Function Monte Carlo simulations with good agreement.Comment: 4 pages, 1 figure, Talk presented at Quark Confinement and the Hadron Spectrum VI, Villasimius, Sardinia, Italy, September 21-25, 200

Dynamical supersymmetry breaking and phase diagram of the lattice Wess-Zumino model

We study dynamical supersymmetry breaking and the transition point by non-perturbative lattice techniques in a class of two-dimensional N=1 Wess-Zumino model. The method is based on the calculation of rigorous lower bounds on the ground state energy density in the infinite-lattice limit. Such bounds are useful in the discussion of supersymmetry phase transition. The transition point is determined with this method and then compared with recent results based on large-scale Green Function Monte Carlo simulations with good agreement.Comment: 6 pages, 4 figs. Lattice2005 (theory), uses Po

Soft tissue healing outcomes in dentistry with acellular dermal collagen matrix

Background and objectives: The collagen matrices are widely used for regeneration procedures alone or in combination with other dental regeneration materials. The aim of this work was to evaluate the soft tissue healing with acellular dermal collagen matrix (ADCM) being used in various defects. Materials and Methods: The ADCM - mucoderm® was used in peri-implant soft tissue augmentation, hard and soft tissue management in immediate restoration and sealing of extraction socket. For that reason, five patients were retrospectively analysed. Results: The collagen matrix underwent active remodelling into new soft tissue and successful soft tissue healing was observed. Conclusion: The use of mucoderm® led to successful soft tissue treatment in various defects

Exact ground state for a class of matrix Hamiltonian models: quantum phase transition and universality in the thermodynamic limit

By using a recently proposed probabilistic approach, we determine the exact ground state of a class of matrix Hamiltonian models characterized by the fact that in the thermodynamic limit the multiplicities of the potential values assumed by the system during its evolution are distributed according to a multinomial probability density. The class includes i) the uniformly fully connected models, namely a collection of states all connected with equal hopping coefficients and in the presence of a potential operator with arbitrary levels and degeneracies, and ii) the random potential systems, in which the hopping operator is generic and arbitrary potential levels are assigned randomly to the states with arbitrary probabilities. For this class of models we find a universal thermodynamic limit characterized only by the levels of the potential, rescaled by the ground-state energy of the system for zero potential, and by the corresponding degeneracies (probabilities). If the degeneracy (probability) of the lowest potential level tends to zero, the ground state of the system undergoes a quantum phase transition between a normal phase and a frozen phase with zero hopping energy. In the frozen phase the ground state condensates into the subspace spanned by the states of the system associated with the lowest potential level.Comment: 31 pages, 13 figure

EVALUATION OF MEASUREMENT UNCERTAINTIES IN THE ASSESSMENT OF THE NOISE IMPACT OF SHIPS

Measurement operations are all inevitably affected by uncertainty, that is defined as the "degree of uncertainty" with which the measurement process obtains the result. It produces a range of values in which the true value of the measurand is present with a certain probability. In the specific case of the evaluation of the acoustic emissions associated with ships, this degree of uncertainty is referable to several causes, better understandable if the measurement procedures indi cated by the reference standards are described (for example ASA (Acoustical Society of America) S12.64-2009/PART 1), adopted for all types of ship (with no limitation in size) that transits at a speed not exceeding 50 kn in deep water. The standard offers three degrees of measurement (A, B or C), which differ in terms of uncertainty, complexity and repeatability. In general, information is given on the characteristics of the instru ments, signal processing and positioning of hydrophones. The standard is valid only in deep water and this represents its main limit: in the case, for example, of very large ships it is difficult to reach the great depths with the instruments. From the analysis of the prescriptions, it clearly follows that noise measurements in water are intrin sically affected by measurement errors that can be reported to the following three macro-types: 1. Error due to the degree of precision of the measurement chain 2. Error due to relative positioning between source and receivers 3. Error due to the characteristics of the measurement environment The 28th International Congress on Sound and Vibration (ICSV28), 24-28 July 2022 2 In the present work, all these possible sources of error have been evaluated on the basis of numerical simulation models whose results have been validated by experimental tests at sea, to arrive at the defi nition of a procedure for estimating the overall error inherent in the measurement and thus defining procedures for the control of the same