Dirac's Footsteps and Supersymmetry

One hundred years after its creator's birth, the Dirac equation stands as the cornerstone of XXth Century physics. But it is much more, as it carries the seeds of supersymmetry. Dirac also invented the light-cone, or "front form" dynamics, which plays a crucial role in string theory and in elucidating the finiteness of N=4 Yang-Mills theory. The light-cone structure of eleven-dimensional supergravity (N=8 supergravity in four dimensions) suggests a group-theoretical interpretation of its divergences. We speculate they could be compensated by an infinite number of triplets of massless higher spin fields, each obeying a Dirac-like equation associated with the coset $F_4/SO(9)$. The divergences are proportional to the trace over a non-compact structure containing the compact form of $F_4$. Its nature is still unknown, but it could show the way to $M$-theory.Comment: Invited Talk at Dirac's Centennial Symposium, Tallahasse, Florida, Dec 200

Kinetic Equations for Baryogenesis via Sterile Neutrino Oscillation

We investigate baryogenesis in the $\nu$MSM (neutrino Minimal Standard Model), which is the MSM extended by three right-handed neutrinos with masses below the electroweak scale. The baryon asymmetry of the universe can be generated by the mechanism via flavor oscillation of right-handed (sterile) neutrinos which are responsible to masses of active neutrinos confirmed by various experiments. We present the kinetic equations for the matrix of densities of leptons which describe the generation of asymmetries. Especially, the momentum dependence of the matrix of densities is taken into account. By solving these equations numerically, it is found that the momentum distribution is significantly distorted from the equilibrium one, since the production for the modes with lower momenta $k \ll T$ ($T$ is the temperature of the universe) is enhanced, while suppressed for higher modes. As a result, the most important mode for the yields of sterile neutrinos as well as the baryon asymmetry is $k \simeq 2 T$, which is smaller than inferred from the thermal average. The comparison with the previous works is also discussed.Comment: 22 pages, 19 figure

Renormalization and resummation in finite temperature field theories

Resummation, ie. reorganization of perturbative series, can result in an inconsistent perturbation theory, unless the counterterms are reorganized in an appropriate way. In this paper two methods are presented for resummation of counterterms: one is a direct method where the necessary counterterms are constructed order by order; the other is a general one, based on renormalization group arguments. We demonstrate at one hand that, in mass independent schemes, mass resummation can be performed by gap equations renormalized prior to the substitution of the resummed mass for its argument. On the other hand it is shown that any (momentum-independent) form of mass and coupling constant resummation is compatible with renormalization, and one can explicitly construct the corresponding counterterms.Comment: 10 pages, 4 figures, revtex

Predicting the onset of rafting of c 0 precipitates by channel deformation in a Ni superalloy

The growth or shrinkage, normal to 001, of the interfaces between the γ matrix and cuboidal γ' precipitates is examined for a Ni-base superalloy, by considering the force acting on the interfaces. The force is produced by the precipitate coherency misfit and the stress produced by plastic deformation in channels of the γ matrix. A simple expression, which directly addresses the origin of the surface force, is given. The plastic deformation within the initially active γ matrix channels exerts the force to cause rafting. The subsequent activation of other types of channels also promotes the rafting in the same direction as the first active channels, when the plastic strain of the former channels increases. These issues are also discussed in terms of analysis based on those dislocations caused by the precipitate misfit and those produced by the plastic deformation

Simple Finite Non-Abelian Flavor Groups

The recently measured unexpected neutrino mixing patterns have caused a resurgence of interest in the study of finite flavor groups with two- and three-dimensional irreducible representations. This paper details the mathematics of the two finite simple groups with such representations, the Icosahedral group A_5, a subgroup of SO(3), and PSL_2(7), a subgroup of SU(3).Comment: 42 pages, matches published version, references adde

2014 European Conference on Donor Health and Management.

The first European Conference on Donor Health and Management was held in the Hague from 3th- 5th September 2014 and hosted by Sanquin, the Dutch national blood donation organization. This is the first international conference with a focus on “donor health”, including donors of blood, organs, and other substances of human origin. The conference covered 5 main themes: Donor Health, Donor Base Management, Donor Recruitment, Donor Retention and Donor Blood Collection. This overview presents selected research topics for each of the five themes.This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1111/tme.1225

Consistent discretization and loop quantum geometry

We apply the ``consistent discretization'' approach to general relativity leaving the spatial slices continuous. The resulting theory is free of the diffeomorphism and Hamiltonian constraints, but one can impose the diffeomorphism constraint to reduce its space of solutions and the constraint is preserved exactly under the discrete evolution. One ends up with a theory that has as physical space what is usually considered the kinematical space of loop quantum geometry, given by diffeomorphism invariant spin networks endowed with appropriate rigorously defined diffeomorphism invariant measures and inner products. The dynamics can be implemented as a unitary transformation and the problem of time explicitly solved or at least reduced to as a numerical problem. We exhibit the technique explicitly in 2+1 dimensional gravity.Comment: 4 pages, Revtex, no figure

Diffusion of an instantaneous plane source in a steady uniform open channel flow

CER61ARC78.December 1961

Graduate education and research

CER61ARC21.Presented at the joint meeting of the Joint Budget Committee and the Legislative Committee on Education Beyond High School of the Colorado General Assembly.Includes bibliographical references (page 32).September 22 and 23, 1961

Dividends and responsibilities of education beyond high school

CER64ARC12.Includes bibliographical references.Presented to Cooperative Consumers Association, December 4, 1963, Kansas City, Missouri.Presented in part to CSU Experiment Station and Extension Service staff, December 5, 1963, Fort Collins, Colorado