448 research outputs found

    Robustness and Predictivity of 4 TeV Unification

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    The stability of the predictions of two of the standard model parameters, α3(MZ)\alpha_3(M_Z) and sin2θ(MZ)\sin^2 \theta(M_Z), in a MU4M_U \sim 4 TeV unification model is examined. It is concluded that varying the unification scale between MU2.5M_U \simeq 2.5 TeV and MU5M_U \simeq 5 TeV leaves robust all predictions within reasonable bounds. Choosing MU=3.8±0.4M_U = 3.8 \pm 0.4 TeV gives, at lowest order, accurate predictions at MZM_Z. Flavor-changing effects and deviations from precision electroweak data are discussed

    Environmental and workplace contamination in the semiconductor industry: implications for future health of the workforce and community.

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    The semiconductor industry has been an enormous worldwide growth industry. At the heart of computer and other electronic technological advances, the environment in and around these manufacturing facilities has not been scrutinized to fully detail the health effects to the workers and the community from such exposures. Hazard identification in this industry leads to the conclusion that there are many sources of potential exposure to chemicals including arsenic, solvents, photoactive polymers and other materials. As the size of the semiconductor work force expands, the potential for adverse health effects, ranging from transient irritant symptoms to reproductive effects and cancer, must be determined and control measures instituted. Risk assessments need to be effected for areas where these facilities conduct manufacturing. The predominance of women in the manufacturing areas requires evaluating the exposures to reproductive hazards and outcomes. Arsenic exposures must also be evaluated and minimized, especially for maintenance workers; evaluation for lung and skin cancers is also appropriate

    Duality without Supersymmetry: The Case of the SO(16)xSO(16) String

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    We extend strong/weak coupling duality to string theories without spacetime supersymmetry, and focus on the case of the unique ten-dimensional, nonsupersymmetric, tachyon-free SO(16)×SO(16)SO(16)\times SO(16) heterotic string. We construct a tachyon-free heterotic string model that interpolates smoothly between this string and the ten-dimensional supersymmetric SO(32)SO(32) heterotic string, and we construct a dual for this interpolating model. We find that the perturbative massless states of our dual theories precisely match within a certain range of the interpolation. Further evidence for this proposed duality comes from a calculation of the one-loop cosmological constant in both theories, as well as the presence of a soliton in the dual theory. This is therefore the first known duality relation between nonsupersymmetric tachyon-free string theories. Using this duality, we then investigate the perturbative and nonperturbative stability of the SO(16)×SO(16)SO(16)\times SO(16) string, and present a conjecture concerning its ultimate fate.Comment: 15 pages, LaTeX, 3 figure

    Reexamination of relaxation of spins due to a magnetic field gradient: Identity of the Redfield and Torrey theories

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    There is an extensive literature on magnetic-gradient-induced spin relaxation. Cates, Schaefer, and Happer, in a seminal publication, have solved the problem in the regime where diffusion theory (the Torrey equation) is applicable using an expansion of the density matrix in diffusion equation eigenfunctions and angular momentum tensors. McGregor has solved the problem in the same regime using a slightly more general formulation using the Redfield theory formulated in terms of the autocorrelation function of the fluctuating field seen by the spins and calculating the correlation functions using the diffusion-theory Green's function. The results of both calculations were shown to agree for a special case. In the present work, we show that the eigenfunction expansion of the Torrey equation yields the expansion of the Green's function for the diffusion equation, thus showing the identity of this approach with that of the Redfield theory. The general solution can also be obtained directly from the Torrey equation for the density matrix. Thus, the physical content of the Redfield and Torrey approaches are identical. We then introduce a more general expression for the position autocorrelation function of particles moving in a closed cell, extending the range of applicability of the theory

    Topological Masses From Broken Supersymmetry

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    We develop a formalism for computing one-loop gravitational corrections to the effective action of D-branes. In particular, we study bulk to brane mediation of supersymmetry breaking in models where supersymmetry is broken at the tree-level in the closed string sector (bulk) by Scherk-Schwarz boundary conditions, while it is realized on a collection of D-branes in a linear or non-linear way. We compute the gravitational corrections to the fermion masses m1/2m_{1/2} (gauginos or goldstino) induced from the exchange of closed strings, which are non-vanishing for world-sheets with Euler characteristic -1 (``genus 3/2'') due to a string diagram with one handle and one hole. We show that the corrections have a topological origin and that in general, for a small gravitino mass, the induced mass behaves as m1/2g4m3/2m_{1/2}\propto g^4 m_{3/2}, with gg the gauge coupling. In generic orbifold compactifications however, this leading term vanishes as a consequence of cancellations caused by discrete symmetries, and the remainder is exponentially suppressed by a factor of exp(1/αm3/22)\exp(-1/\alpha'm^2_{3/2}).Comment: 33 pages, 5 figures. v2 is the final Nuclear Physics B version including an additional reference and some minor correction

    Real Special Geometry

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    We give a coordinate-free description of real manifolds occurring in certain four dimensional supergravity theories with antisymmetric tensor fields. The relevance of the linear multiplets in the compactification of string and five-brane theories is also discussed.Comment: 10 pgs (TeX with Harvmac), CERN-TH.7211/94, UCLA/94/TEP/14, POLFIS-TH.01/9