337931
The Scaling limit of the energy correlations in non integrable Ising models
We obtain an explicit expression for the multipoint energy correlations of a non solvable two-dimensional Ising models with nearest neighbor ferromagnetic interactions plus a weak finite range interaction of strength �, in a scaling limit in which we send the lattice spacing to zero and the temperature to the critical one. Our analysis is based on an exact mapping of the model into an interacting lattice fermionic theory, which generalizes the one originally used by Schultz, Mattis and Lieb for the nearest neighbor Ising model. The interacting model is then analyzed by a multiscale method first proposed by Pinson and Spencer. If the lattice spacing is finite, then the correlations cannot be computed in closed form: rather, they are expressed in terms of infinite, convergent, power series in �. In the scaling limit, these infinite expansions radically simplify and reduce to the limiting energy correlations of the integrable Ising model, up to a finite renormalization of the parameters. Explicit bounds on the speed of convergence to the scaling limit are derived.
14496666
Lattice gauge theory model for graphene
The effects of the electromagnetic (em) electron-electron interactions in half-filled graphene are investigated in terms of a lattice gauge theory model. By using exact renormalization group methods and lattice Ward identities, we show that the em interactions amplify the responses to the excitonic pairings associated to a Kekule distortion and to a charge-density wave. The effect of the electronic repulsion on the Peierls-Kekule instability, usually neglected, is evaluated by deriving an exact non BCS gap equation, from which we find evidence that strong em interactions among electrons facilitate the spontaneous distortion of the lattice and the opening of a gap.
17981665
Absolute stability limit for relativistic charged spheres
We find an exact solution for the stability limit of relativistic charged spheres for the case of constant gravitational mass density and constant charge density. We argue that this provides an absolute stability limit for any relativistic charged sphere in which the gravitational mass density decreases with radius and the charge density increases with radius. We then provide a cruder absolute stability limit that applies to any charged sphere with a spherically symmetric mass and charge distribution. We give numerical results for all cases. In addition, we discuss the example of a neutral sphere surrounded by a thin, charged shell.
119110967
Performances of a large mass ZnSe bolometer to search for rare events
Scintillating bolometers of ZnSe are the baseline choice of the LUCIFER experiment, whose aim is to observe the neutrinoless double beta decay of 82Se. The independent read-out of the heat and scintillation signals allows to identify and reject α particle interactions, the dominant background source for bolometric detectors. In this paper we report the performances of a ZnSe crystal operated within the LUCIFER R&D. We measured the scintillation yield, the energy resolution and the background in the energy region where the signal from 0νDBD decay of 82Se is expected with an exposure of 9.4 kgdays. With a newly developed analysis algorithm we improved the rejection of α events, and we estimated the increase in energy resolution obtained by the combination of the heat and light signals. For the first time we measured the light emitted by nuclear recoils, and found it to be compatible with zero. We conclude that the discrimination of nuclear recoils from β/γ interactions in the WIMPs energy region is possible, but low-noise light detectors are needed.
126109680
Bolometric light detectors for Neutrinoless Double Beta Decay search
Margherita TENCONI∗,ab Dmitry CHERNYAK,abc Fedor DANEVICH,c Andrea GIULIANI,ad Michele MANCUSO,ad Stefanos MARNIEROS,a Emiliano OLIVIERI,a Claudia RUSCONIde aCentre de Spectrometrie Nucleaire et de Spectrometrie de Masse F-91405 Orsay, France bUniversite Paris-Sud F-91405 Orsay, France cInstitute for Nuclear Research MSP 0368 Kyiv, Ukraine dUniversita degli Studi dell’Insubria, Dipartimento di Fisica e Matematica I-22100 Como, Italy eIstituto Nazionale di Fisica Nucleare, Sezione di Milano-Bicocca I-20126 Milano, Italy
118915062
Dark matter search with innovative techniques
118432063
AGILE observations of Supernova Remnants
We will review the crucial AGILE gamma-ray SNR observations focusing on the evidence of hadronic cosmic-ray acceleration that has been obtained so far. We discuss data on SNR IC443, W28 and W44. We show that in all cases a consistent model of hadronic acceleration and interaction with gaseous surroundings can be used to successfully explain the quite complex morphology and spectral characteristics of the sources. AGILE, with its crucially important sensitivity near 100 MeV, is equipped to prove the existence of pi-zero emission.
119243574
Composite macro-bolometers for the rejection of surface radioactive background in rare-event experiments
Experiments searching for rare events, such as neutrinoless double beta decay and interactions of dark matter candidates, require extremely low levels of background. When these experiments are performed using macro-bolometers, radioactive contamination near the surfaces is of particular concern. For a bolometric neutrinoless double beta decay experiment, it can cause counts in the spectral region where the signal is expected, while for a dark matter experiment which exploits ionization signals for particle identification, it originates an incomplete charge collection simulating a nuclear recoil. In order to control the effects of surface contamination, we developed a novel technique that uses composite macro-bolometers to identify energy depositions that occur close to the surfaces of materials immediately surrounding the detector. The composite macro-bolometer proposed and studied here consists of a main energy absorber that is thermally coupled to and entirely surrounded by thin absorbers that act as active shields. Surface energy depositions can be rejected by the analysis of simultaneous signals in the main absorber and the shields. In this paper, we describe a full thermal model and experimental results for three prototype detectors. The detectors consist of Ge, Si, or TeO2 thin absorbers as active shields, all with TeO2 crystals as main absorbers. In all cases, the surface event rejection capability is clearly demonstrated. In addition, simulations and preliminary results show that it is possible to detect energy depositions that occurred on the shields without separate readout channels for them. The energy depositions in the shields are distinguished from those in the main absorber through pulse shape discrimination. This simplification makes this technique a viable method for the rejection of surface energy depositions in next-generation bolometric double beta decay searches, such as possible extensions or upgrades of the CUORE experiment.