The Imprint of Gravitational Waves on the Cosmic Microwave Background

Long-wavelength gravitational waves can induce significant temperature anisotropy in the cosmic microwave background. Distinguishing this from anisotropy induced by energy density fluctuations is critical for testing inflationary cosmology and theories of large-scale structure formation. We describe full radiative transport calculations of the two contributions and show that they differ dramatically at angular scales below a few degrees. We show how anisotropy experiments probing large- and small-angular scales can combine to distinguish the imprint due to gravitational waves.Comment: 11 pages, Penn Preprint-UPR-

Note on Varying Speed of Light Cosmologies

The various requirements on a consistent varying speed of light (`VSL') theory are surveyed, giving a short check-list of issues that should be satisfactorily handled by such theories.Comment: 6 pages; to appear in the GRG Journa

Search for Barents: Evaluation of Possible Burial Sites on North Novaya Zemlya, Russia

Three cairns on northernmost Novaya Zemlya identified as possible rock-pile graves by Russian investigators in 1977 and 1988 were located and inspected for human remains. These cairns are in the area visited by Dutch seafarers between 17 and 22 June 1597, after their wintering on Novaya Zemlya, and may contain the body of Willem Barents. Barents and one of his crewmen died on 20 June 1597 while the winterers were on landfast ice close to shore. Previous research on Spitsbergen and contemporary reports on the efforts of 16th and 17th century Dutch seafarers to prepare a Christian grave led us to conclude that the deceased probably were buried on the beach, possibly in a shallow grave or a snowbank. Inspection of the area indicates that this grave probably was destroyed by high (5+ m asl) wave run-up during storms, cryogenic erosion, and animals (polar bear, fox). None of the cairns, or any of several other prominent rock piles in the ~180 km long search area, contained human remains or had lichen growths that would indicate construction ~400 years ago (>2 cm, Rhizocarpon sp.). Cairns were not reported by the Dutch in 1594-98, and most of those encountered on northern Novaya Zemlya probably date from exploration after ca. 1860, when the region north of ~76°N became accessible in a warming, post-Little Ice Age climate.Trois cairns situés aux confins septentrionaux de la Nouvelle-Zemble et identifiés en 1977 et 1988 par des chercheurs russes comme pouvant signaler des amas de pierres funéraires ont été localisés et ont fait l'objet d'une inspection en vue de déterminer s'ils renfermaient des restes humains. Ces cairns se trouvent dans la région visitée par des navigateurs néerlandais entre le 17 et le 22 juin 1597, après leur hivernage en Nouvelle-Zemble, et ils auraient pu contenir le corps de Willem Barents. Ce dernier et un membre de son équipage périrent le 20 juin 1597, alors que les hivernants se trouvaient sur la glace près du rivage. Des recherches antérieures sur le Spitzberg et des rapports contemporains sur les efforts des marins néerlandais des XVIe et XVIIe siècles en vue de préparer une sépulture chrétienne nous amènent à la conclusion que les défunts ont probablement été enterrés sur la plage, voire dans une tombe peu profonde ou un amoncellement de neige. Un examen du site indique que cette tombe a probablement été détruite par un assaut puissant (+ 5 m ASL) des vagues au cours de tempêtes, par l'érosion cryogénique et par les animaux (ours polaire, renard). Aucun des cairns, et aucun des autres amas de rochers bien visibles situés dans la région de l'étude, qui s'étendait sur une longueur d'environ 180 km, ne renfermait de vestiges humains ou n'affichait une croissance lichénique qui aurait indiqué une construction remontant à près de 400 ans (> 2 cm, Rhizocarpon sp.) Les Néerlandais n'ont pas rapporté la présence de cairns entre 1594 et 1598 et ceux que l'on a retrouvés en Nouvelle-Zemble septentrionale datent probablement des explorations qui eurent lieu après environ 1860, quand la région située en gros au nord du 76° de latit. N. est devenue accessible dans le contexte d'un réchauffement climatique survenu au petit âge glaciaire

Leptogenesis through direct inflaton decay to light particles

We present a scenario of nonthermal leptogenesis following supersymmetric hybrid inflation, in the case where inflaton decay to both heavy right handed neutrino and SU(2)_L triplet superfields is kinematically disallowed. Lepton asymmetry is generated through the decay of the inflaton into light particles by the interference of one-loop diagrams with right handed neutrino and SU(2)_L triplet exchange respectively. We require superpotential couplings explicitly violating a U(1) R-symmetry and R-parity. However, the broken R-parity need not have currently observable low-energy signatures. Also, the lightest sparticle can be stable. Some R-parity violating slepton decays may, though, be detectable in the future colliders. We take into account the constraints from neutrino masses and mixing and the preservation of the primordial lepton asymmetry.Comment: 11 pages including 3 figures, uses Revtex, minor corrections, references adde

Quantum computation and the physical computation level of biological information processing

On the basis of introspective analysis, we establish a crucial requirement for the physical computation basis of consciousness: it should allow processing a significant amount of information together at the same time. Classical computation does not satisfy the requirement. At the fundamental physical level, it is a network of two body interactions, each the input-output transformation of a universal Boolean gate. Thus, it cannot process together at the same time more than the three bit input of this gate - many such gates in parallel do not count since the information is not processed together. Quantum computation satisfies the requirement. At the light of our recent explanation of the speed up, quantum measurement of the solution of the problem is analogous to a many body interaction between the parts of a perfect classical machine, whose mechanical constraints represent the problem to be solved. The many body interaction satisfies all the constraints together at the same time, producing the solution in one shot. This shades light on the physical computation level of the theories that place consciousness in quantum measurement and explains how informations coming from disparate sensorial channels come together in the unity of subjective experience. The fact that the fundamental mechanism of consciousness is the same of the quantum speed up, gives quantum consciousness a potentially enormous evolutionary advantage.Comment: 13 page

Background Thermal Contributions in Testing the Unruh Effect

We consider inertial and accelerated Unruh-DeWitt detectors moving in a background thermal bath and calculate their excitation rates. It is shown that for fast moving detectors such a thermal bath does not affect substantially the excitation probability. Our results are discussed in connection with a possible proposal of testing the Unruh effect in high energy particle accelerators.Comment: 13 pages, (REVTEX 3.0), 3 figures available upon reques

Electronic excitations and the tunneling spectra of metallic nanograins

Tunneling-induced electronic excitations in a metallic nanograin are classified in terms of {\em generations}: subspaces of excitations containing a specific number of electron-hole pairs. This yields a hierarchy of populated excited states of the nanograin that strongly depends on (a) the available electronic energy levels; and (b) the ratio between the electronic relaxation rate within the nano-grain and the bottleneck rate for tunneling transitions. To study the response of the electronic energy level structure of the nanograin to the excitations, and its signature in the tunneling spectrum, we propose a microscopic mean-field theory. Two main features emerge when considering an Al nanograin coated with Al oxide: (i) The electronic energy response fluctuates strongly in the presence of disorder, from level to level and excitation to excitation. Such fluctuations produce a dramatic sample dependence of the tunneling spectra. On the other hand, for excitations that are energetically accessible at low applied bias voltages, the magnitude of the response, reflected in the renormalization of the single-electron energy levels, is smaller than the average spacing between energy levels. (ii) If the tunneling and electronic relaxation time scales are such as to admit a significant non-equilibrium population of the excited nanoparticle states, it should be possible to realize much higher spectral densities of resonances than have been observed to date in such devices. These resonances arise from tunneling into ground-state and excited electronic energy levels, as well as from charge fluctuations present during tunneling.Comment: Submitted to the Physical Review

DFT calculation of the intermolecular exchange interaction in the magnetic Mn4_4 dimer

The dimeric form of the single-molecule magnet [Mn$_4$O$_3$Cl$_4$(O$_2$CEt)$_3$(py)$_3$]$_2$ recently revealed interesting phenomena: no quantum tunneling at zero field and tunneling before magnetic field reversal. This is attributed to substantial antiferromagnetic exchange interaction between different monomers. The intermolecular exchange interaction, electronic structure and magnetic properties of this molecular magnet are calculated using density-functional theory within generalized-gradient approximation. Calculations are in good agreement with experiment.Comment: 4 page