Search

If there is a population of black holes distributed randomly in space, light rays passing in their vicinity will acquire random phases. In the "two-slit" model of an interferometer this can, for a high density of black holes, lead to a diffusion in the phase difference between the two arms of the interferometer and thus to a loss of coherence or "visibility" in interferometric observations. Hence the existence of "fringe contrast" or "visibility" in interferometric observations can be used to put a limit on the possible presence of black holes along the flight path. We give a formula for this effect and consider its application, particularly for observations in cosmology. Under the assumption that the dark matter consists of primordial black holes, we consider sources at high z , up to the CMB. While the strongest results are for the CMB as the most remote source, more nearby sources at high z lead to similar effects. The effect increases with the baseline, and in the limiting case of the CMB we find that with earth-size baselines a nonzero "visibility" would limit the mass of possible primordial black holes, to approximately M ∕ M ⊙ ≤ 1 0 − 1 . Although such limits would not appear to be as strong as those obtained, say from microlensing, they involve a much different methodology and are dominated by very early times (see Table 1). Longer baselines lead to more stringent limits and in principle with extreme lengths, the method could possibly find positive evidence for primordial black holes. In this case, however, all other kinds of phase averaging would have to be constrained or eliminated. [ABSTRACT FROM AUTHOR]

Advances in high angular resolution astronomy make it conceivable that black hole dark matter could be detected via angular deviation effects. Assuming the dark matter in the galaxy is made of solar mass black holes, there is a nontrivial probability that a line-of-sight through the galaxy, leads to μ arcsec 's deviations, a value that has been discussed for various astronomical projects. In cosmology, the effects are magnified by an increased density at early times and an opening of angles due to redshift. We stress the interest of the resolution in observations on the CMB and emphasize the distinction between this and the power spectrum. If the dark matter is made of primordial black holes, present at the CMB, random deflections of the CMB photons lead to a limit on the angular resolution, approximately 3 × 1 0 − 7 M / M ⊙  rad, with M the mass of the black holes. Using the resolutions of ∼ 1 0 − 3 rad demonstrated in observations of the "acoustic peaks" then implies the limit (M / M ⊙) ≲ 1 0 7 . While this large value seems uninteresting, improved resolutions would lead to significant exclusion limits or conceivably the discovery of primordial black holes. [ABSTRACT FROM AUTHOR]

The description of very high energy proton–proton cross-sections in terms of a "black disc" with an "edge" allows a simple generalization to highest energy proton–nucleus cross-sections. This results in a leading ln2W term and a ln W term whose coefficient depends linearly on the radius of the nucleus (W the c.m. energy). The necessary parameters are determined from the fits to p–p data. Since the coefficient of the ln W term is rather large, it is doubtful that the regime of ln2W dominance can be reached with available energies in accelerators or cosmic rays. However, the ln W term can be relevant for highest energy cosmic rays in the atmosphere, where a large increase for the cross-section on nitrogen is expected. Tests of the theory should be possible by studying the coefficient of ln W at p-nucleus colliders. [ABSTRACT FROM AUTHOR]

Analysis of the data for proton and antiproton scattering leads to a simple picture for very high energy hadronic cross-sections. There is, asymptotically, a simple 'black disc' with a smooth 'edge'. The radius of the 'disc' is expanding logarithmically with energy, while the 'edge' is constant. These conclusions follow from extensive fits to accelerator and cosmic ray data, combined with the observation that a certain combination of elastic and total cross-sections allows extraction of the 'edge'. An interesting feature of the results is that the 'edge' is rather large compared to the 'disc'. This explains the slow approach to 'asymptopia' where the 'disc' finally dominates. [ABSTRACT FROM AUTHOR]

Identifying the nature and origin of dark matter is one of the major challenges for modern astro and particle physics. Direct dark-matter searches aim at an observation of dark-matter particles interacting within detectors. The focus of several such searches is on interactions with nuclei as provided e.g. by weakly interacting massive particles. However, there is a variety of dark-matter candidates favoring interactions with electrons rather than with nuclei. One example are dark photons, i.e., long-lived vector particles with a kinetic mixing to standard-model photons. In this work we present constraints on this kinetic mixing based on data from CRESST-II Phase 2 corresponding to an exposure before cuts of 52 kg-days. These constraints improve the existing ones for dark-photon masses between 0.3 and 0.7 keV/c $$^2$$ . [ABSTRACT FROM AUTHOR]

We reconsider the Euclidean version of the photon number integral introduced by Stodolsky [Acta Phys. Pol. B 33, 2659 (2002), e-print hep-th/02053131].This integral is well defined for any smooth non-self-intersecting curve in RN. Besides studying general features of this integral (including its conformal invariance), we evaluate it explicitly for the ellipse. The result is nellipse=(ξ-1+ξ)π2, where ξ is the ratio of the minor and major axes. This is in agreement with the previous result ncircle=2π2 and also with the conjecture that the minimum value of n for any plane curve occurs for the circle. [ABSTRACT FROM AUTHOR]

A simulation of decoherence as random noise in the Hamiltonian is studied. The full Hamiltonian for the rf Squid is used, with the parameters chosen such that there is a double-potential well configuration where the two quasi-degenerate lowest levels are well separated from the rest. The results for these first two levels are in quantitative agreement with expectations from the ‘spin 1/2’ picture for the behaviour of a two-state system. [ABSTRACT FROM AUTHOR]

We present our recent experiments on macroscopic tunneling in the quantum regime for underdamped Josephson junctions with different classical-quantum crossover temperatures. These experiments are performed towards the observation of macroscopic quantum coherence in Josephson systems. A new method to measure coherence in a two-level system based on the adiabatic inversion in an rf squid, is presented. This approach could open new perspectives in view of realization of an elementary quantum bit. [ABSTRACT FROM AUTHOR]

Neutrino bursts from supernova explosions would offer a novel opportunity to study the masses and mixings of neutrinos. In this paper we would like to examine, on the basis of a definite supernova model, the various effects which might exist and how they could be observed. [ABSTRACT FROM AUTHOR]

Discusses the use of low-temperature techniques to detect medium- and low-energy neutrinos as well as the dark matter of the universe. Coherent neutrino scattering; Neutral currents, solar and terrestrial; Detection of dark matter; Double beta decay studies; First results on dark matter; Low-temperature devices; Nonequilibrium devices; Potential low-energy frontier.

Develops a detector consisting of a cryogenic calorimeter with a scintillating crystal as an absorber and a second calorimeter for the detection of a scintillation light. Discrimination between nuclear recoils and electron recoils under a specific suppression factor; Applications of the research for background rejection in matter research.

Pays tribute to the late Hans Ekstein, a physicist at Argonne National Laboratory and known for his work on scattering theory and the foundations of symmetry.