Fundamental constraints on particle tracking with optical tweezers

A general quantum limit to the sensitivity of particle position measurements is derived following the simple principle of the Heisenberg microscope. The value of this limit is calculated for particles in the Rayleigh and Mie scattering regimes, and with parameters which are relevant to optical tweezers experiments. The minimum power required to observe the zero-point motion of a levitating bead is also calculated, with the optimal particle diameter always smaller than the wavelength. We show that recent optical tweezers experiments are within two orders of magnitude of quantum limited sensitivity, suggesting that quantum optical resources may soon play an important role in high sensitivity tracking applications

Coulomb force effects in low-energy α\alpha-deuteron scattering

The $\alpha$-proton Coulomb interaction is included in the description of $\alpha$-deuteron scattering using the screening and renormalization approach in the framework of momentum-space three-particle equations. The technical reliability of the method is demonstrated. Large Coulomb-force effects are found.Comment: To be published in Phys. Rev.

On The Interaction Of D0-Brane Bound States And RR Photons

We consider the problem of the interaction between D0-brane bound state and 1-form RR photons by the world-line theory. Based on the fact that in the world-line theory the RR gauge fields depend on the matrix coordinates of D0-branes, the gauge fields also appear as matrices in the formulation. At the classical level, we derive the Lorentz-like equations of motion for D0-branes, and it is observed that the center-of-mass is colourless with respect to the SU(N) sector of the background. Using the path integral method, the perturbation theory for the interaction between the bound state and the RR background is developed. We discuss what kind of field theory may be corresponded to the amplitudes which are calculated by the perturbation expansion in world-line theory. Qualitative considerations show that the possibility of existence of a map between the world-line theory and the non-Abelian gauge theory is very considerable.Comment: LaTeX, 28 pages, 4 eps figures. v2 and v3: eqs. (3.18) and (B.2) are corrected, very small change

Dispersion of biased swimming microorganisms in a fluid flowing through a tube

Classical Taylor-Aris dispersion theory is extended to describe the transport of suspensions of self-propelled dipolar cells in a tubular flow. General expressions for the mean drift and effective diffusivity are determined exactly in terms of axial moments, and compared with an approximation a la Taylor. As in the Taylor-Aris case, the skewness of a finite distribution of biased swimming cells vanishes at long times. The general expressions can be applied to particular models of swimming microorganisms, and thus be used to predict swimming drift and diffusion in tubular bioreactors, and to elucidate competing unbounded swimming drift and diffusion descriptions. Here, specific examples are presented for gyrotactic swimming algae.Comment: 20 pages, 4 figures. Published version available at http://rspa.royalsocietypublishing.org/content/early/2010/02/09/rspa.2009.0606.short?rss=

Self-sterilization of bodies during outer planet entry

A body encountering the atmosphere of an outer planet is subjected to heat loads which could result in high temperature conditions that render terrestrial organisms on or within the body nonviable. To determine whether an irregularly shaped entering body, consisting of several different materials, would be sterilized during inadvertent entry at high velocity, the thermal response of a typical outer planet spacecraft instrument was studied. The results indicate that the Teflon insulated cable and electronic circuit boards may not experience sterilizing temperatures during a Jupiter, Saturn, or Titan entry. Another conclusion of the study is that small plastic particles entering Saturn from outer space have wider survival corridors than do those at Jupiter

Gauge Invariant Effective Stress-Energy Tensors for Gravitational Waves

It is shown that if a generalized definition of gauge invariance is used, gauge invariant effective stress-energy tensors for gravitational waves and other gravitational perturbations can be defined in a much larger variety of circumstances than has previously been possible. In particular it is no longer necessary to average the stress-energy tensor over a region of spacetime which is larger in scale than the wavelengths of the waves and it is no longer necessary to restrict attention to high frequency gravitational waves.Comment: 11 pages, RevTe

Study of the spring and autumn daemon-flux maxima at the Baksan Neutrino Observatory

Detection of daemons in low-background conditions in September 2005 and March 2006 has provided evidence for the expected to occur at that times maxima in the flux of daemons with V ~ 10-15 km s-1, which hit the Earth from near-Earth, almost circular heliocentric orbits. The ability of some FEU-167-1 PM tubes with a thicker inner Al coating to detect directly daemon passage through them has also been demonstrated, an effect increasing ~100-fold the detector efficiency. As a result, the daemon flux recorded at the maxima was increased from ~10-9 to ~10-7 cm-2 s-1. The intensity and direction of the flux during maxima depend on the time of day and latitude of observations (therefore, synchronous measurements in the Northern and Southern Earth's hemispheres are desirable). All the experimental results obtained either support the conclusions following from the daemon paradigm or find a simple interpretation within it.Comment: 15 pages, including 8 figures and 3 table

The diffuse neutrino flux from the inner Galaxy: constraints from very high energy gamma-ray observations

Recently, the MILAGRO collaboration reported on the detection of a diffuse multi-TeV emission from a region of the Galactic disk close to the inner Galaxy. The emission is in excess of what is predicted by conventional models for cosmic ray propagation, which are tuned to reproduce the spectrum of cosmic rays observed locally. By assuming that the excess detected by MILAGRO is of hadronic origin and that it is representative for the whole inner Galactic region, we estimate the expected diffuse flux of neutrinos from a region of the Galactic disk with coordinates $-40^{\circ} < l < 40^{\circ}$. Our estimate has to be considered as the maximal expected neutrino flux compatible with all the available gamma ray data, since any leptonic contribution to the observed gamma-ray emission would lower the neutrino flux. The diffuse flux of neutrinos, if close to the maximum allowed level, may be detected by a km$^3$--scale detector located in the northern hemisphere. A detection would unambiguously reveal the hadronic origin of the diffuse gamma-ray emission.Comment: submitted to Astroparticle Physic