Goldstone bosons and a dynamical Higgs field

Higgs inflation uses the gauge variant Higgs field as the inflaton. During inflation the Higgs field is displaced from its minimum, which results in associated Goldstone bosons that are apparently massive. Working in a minimally coupled U(1) toy model, we use the closed-time-path formalism to show that these Goldstone bosons do contribute to the one-loop effective action. Therefore the computation in unitary gauge gives incorrect results. Our expression for the effective action is gauge invariant upon using the background equations of motion.Comment: 27 pages, 2 figures, published version with minor correction

Nonperturbative late time asymptotics for heat kernel in gravity theory

Recently proposed nonlocal and nonperturbative late time behavior of the heat kernel is generalized to curved spacetimes. Heat kernel trace asymptotics is dominated by two terms one of which represents a trivial covariantization of the flat-space result and another one is given by the Gibbons-Hawking integral over asymptotically-flat infinity. Nonlocal terms of the effective action generated by this asymptotics might underly long- distance modifications of the Einstein theory motivated by the cosmological constant problem. New mechanisms of the cosmological constant induced by infrared effects of matter and graviton loops are briefly discussed.Comment: 22 pages, LaTeX, final version, to be published in Phys. Rev.

Single-Spin Measurement and Decoherence in Magnetic Resonance Force Microscopy

We consider a simple version of a cyclic adiabatic inversion (CAI) technique in magnetic resonance force microscopy (MRFM). We study the problem: What component of the spin is measured in the CAI MRFM? We show that the non-destructive detection of the cantilever vibrations provides a measurement of the spin component along the effective magnetic field. This result is based on numerical simulations of the Hamiltonian dynamics (the Schrodinger equation) and the numerical solution of the master equation.Comment: 5 pages + 5 figures (PNG format

Electrical lnsulative Properties of Some Agro-Waste Material~.

Insulating materials are used in electrical power circuits to prevent leakages of current. This work investigates the possibility of using agro-waste materials: shells of coconut, mango endocarp, palm kernel, groundnut and bean as well as corncob and rice husk, as electrical insulators. Accordingly, electrical insulative properties: dielectric strength, resistivity, dielectric constant, moisture content and water absorption capacity of these waste materials were determined Each of the materials was washed, air dried for 2 weeks, ground into powder, and sieved with, the U.S Standard Sieve No. 40. It was then bound with a 200 gllitre aqueous solution of gum Arabic, and moulded into various shapes and thicknesses which were air dried for a week. Their dielef:tric strengths were tested thereafter, using a variable trarisformer tester; their resistivities measured with an i41sulation tester, while both moisture contents and water absoiption capacities were determined gravimetrically on dry weight basis. The results showed that the electrical insulative properties of these materials were C011Jparable with the known standard values. However, their moisture contents and water absorption capacities were relatively high, thereby limiting their usefulness as insulators in their ordinary states. Based on their dielectric constants and a standard table, coconut, palm kemel and groundnut shells, with dielectric constants range of 3.5-5.5 fall into high voltage applications; mango shell, corncob, rice lntsk and bean shell, with dielectric constants less than 3. 0, fall into the low voltage application category

Quantum geometrodynamics: whence, whither?

Quantum geometrodynamics is canonical quantum gravity with the three-metric as the configuration variable. Its central equation is the Wheeler--DeWitt equation. Here I give an overview of the status of this approach. The issues discussed include the problem of time, the relation to the covariant theory, the semiclassical approximation as well as applications to black holes and cosmology. I conclude that quantum geometrodynamics is still a viable approach and provides insights into both the conceptual and technical aspects of quantum gravity.Comment: 25 pages; invited contribution for the Proceedings of the seminar "Quantum Gravity: Challenges and Perspectives", Bad Honnef, Germany, April 200

Aharonov-Bohm oscillations of a particle coupled to dissipative environments

The amplitude of the Bohm-Aharonov oscillations of a particle moving around a ring threaded by a magnetic flux and coupled to different dissipative environments is studied. The decay of the oscillations when increasing the radius of the ring is shown to depend on the spatial features of the coupling. When the environment is modelled by the Caldeira-Leggett bath of oscillators, or the particle is coupled by the Coulomb potential to a dirty electron gas, interference effects are suppressed beyond a finite length, even at zero temperature. A finite renormalization of the Aharonov-Bohm oscillations is found for other models of the environment.Comment: 6 page

Short Communication Report: An analysis of Human African Trypanosomiasis (HAT) in Nigeria.

No Abstrac

Transient Dynamics in Magnetic Force Microscopy for a Single-Spin Measurement

We analyze a single-spin measurement using a transient process in magnetic force microscopy (MFM) which could increase the maximum operating temperature by a factor of Q (the quality factor of the cantilever) in comparison with the static Stern-Gerlach effect. We obtain an exact solution of the master equation, which confirms this result. We also discuss the conditions required to create a macroscopic Schrodinger cat state in the cantilever.Comment: 22 pages 2 figure