882 research outputs found
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
. The divergences are proportional to the trace over a non-compact
structure containing the compact form of . Its nature is still unknown,
but it could show the way to -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 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 ( 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 , 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
Recommended from our members
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
Diffusion of an instantaneous plane source in a steady uniform open channel flow
CER61ARC78.December 1961
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
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
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
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