Intercontinental clock synchronization with the block 1 VLBI system

The Block 1 very long baseline interferometer (VLBI) operated by the Deep Space Network (DSN) to make weekly measurements of the relative epoch and rate offsets between the time standards in the global network of DSN stations is discussed. The precision of these measurements routinely achieves sub-microsecond levels for epoch offset and accuracies of better than one part in 10 to the 12th power for rate offset. The implementation of the phase calibrator system permits absolute measurement of epoch offset to better than 10 nanoseconds. With the near-real-time play-back and on-line storage of VLBI data, the Block 1 system typically produces clock parameters within 48 hours from the time of observation

Fault-Tolerant Dot-Product Engines

Coding schemes are presented that provide the ability to correct and detect computational errors while using dot-product engines for integer vector--matrix multiplication. Both the $L_1$-metric and the Hamming metric are considered

Space cabin atmospheres

Space cabin atmospheres - physical and physiological variable

Microwave radiation

Physiological effects of microwave radiation on animals and humans and establishment of human tolerance limit

Water

Water requirements for manned space flight in relation to water balance and purit

Electroweak corrections to e+ e- -> nu anti-nu H and e+ e- -> t anti-t H

The most interesting Higgs-production processes at future e+ e- colliders belong to the process class e+ e- -> f anti-f H. We study the full O(alpha) corrections to this reaction in the Standard Model for neutrinos and top quarks in the final state. Leading higher-order corrections from initial-state radiation and QCD corrections are also taken into account. Although cancellations between the different kinds of corrections occur, the full corrections are of the order of +/-10% and thus important ingredients in the theoretical predictions for future e+ e- colliders.Comment: 3 pages, LaTeX, 4 postscript figures, talk given at the EPS conference, Aachen, 200

Electroweak radiative corrections to e+ e- -> t anti-t H

We have calculated the complete electroweak O(alpha) radiative corrections to the Higgs-boson production process e+ e- -> t anti-t H in the electroweak Standard Model. Initial-state radiation beyond O(alpha) is included in the structure-function approach. The calculation of the corrections is briefly described, and numerical results are presented for the total cross section. Both the photonic and the genuine weak corrections reach the order of about 10% or even more and show a non-trivial dependence on the Higgs-boson mass and on the scattering energy. We compare our results with two previous calculations that obtained differing results at high energies.Comment: 13 pages, LaTeX, 12 postscript figure

An upper bound from helioseismology on the stochastic background of gravitational waves

The universe is expected to be permeated by a stochastic background of gravitational radiation of astrophysical and cosmological origin. This background is capable of exciting oscillations in solar-like stars. Here we show that solar-like oscillators can be employed as giant hydrodynamical detectors for such a background in the muHz to mHz frequency range, which has remained essentially unexplored until today. We demonstrate this approach by using high-precision radial velocity data for the Sun to constrain the normalized energy density of the stochastic gravitational-wave background around 0.11 mHz. These results open up the possibility for asteroseismic missions like CoRoT and Kepler to probe fundamental physics.Comment: 6 pages, 2 figures. Updated to match published versio

Improved Nearly-MDS Expander Codes

A construction of expander codes is presented with the following three properties: (i) the codes lie close to the Singleton bound, (ii) they can be encoded in time complexity that is linear in their code length, and (iii) they have a linear-time bounded-distance decoder. By using a version of the decoder that corrects also erasures, the codes can replace MDS outer codes in concatenated constructions, thus resulting in linear-time encodable and decodable codes that approach the Zyablov bound or the capacity of memoryless channels. The presented construction improves on an earlier result by Guruswami and Indyk in that any rate and relative minimum distance that lies below the Singleton bound is attainable for a significantly smaller alphabet size.Comment: Part of this work was presented at the 2004 IEEE Int'l Symposium on Information Theory (ISIT'2004), Chicago, Illinois (June 2004). This work was submitted to IEEE Transactions on Information Theory on January 21, 2005. To appear in IEEE Transactions on Information Theory, August 2006. 12 page

Effect of hybridization on the magnetic properties of correlated two-band metals

The magnetic properties of transition-like metals are discussed within the single site approximation, which is a picture to take into account electron correlations. The metal is described by two hybridized bands one of which includes Coulomb correlation. The presented results indicate that ferromagnetism arises for adequate values of hybridization (V), correlation (U) and occupation number($n_{\sigma}$). Some similarities with Dynamical Mean-Field Theory (DMFT) are indicated.Comment: 3 pages, 3 figures, presented at the 53rd MMM08 conference in Austin, 200