Neutrinos, Weak Interactions, and r-process Nucleosynthesis

Two of the key issues in understanding the neutron-to-proton ratio in a core-collapse supernova are discussed. One of these is the behavior of the neutrino-nucleon cross sections as supernova energies. The other issue is the many-body properties of the neutrino gas near the core when both one- and two-body interaction terms are included.Comment: To be published in the Proceedings of "International Symposium on Structure of Exotic Nuclei and Nuclear Forces (SENUF 06)", March 2006, Tokyo, Japa

An S3S_3 Model for Lepton Mass Matrices with Nearly Minimal Texture

We propose a simple extension of the electroweak standard model based on the discrete $S_3$ symmetry that is capable of realizing a nearly minimal Fritzsch-type texture for the Dirac mass matrices of both charged leptons and neutrinos. This is achieved with the aid of additional $Z_5$ and $Z_3$ symmetries, one of which can be embedded in $U(1)_{B-L}$. Five complex scalar singlet fields are introduced in addition to the SM with right-handed neutrinos. Although more general, the modified texture of the model retains the successful features of the minimal texture without fine-tuning; namely, it accommodates the masses and mixing of the leptonic sector and relates the emergence of large leptonic mixing angles with the seesaw mechanism. For large deviations of the minimal texture, both quasidegenerate spectrum or inverted hierarchy are allowed for neutrino masses.Comment: 11pp, 2 figures. v2: vev alignment addressed, additional analysis performed; to appear in PR

Dynamics, Rectification, and Fractionalization for Colloids on Flashing Substrates

We show that a rich variety of dynamic phases can be realized for mono- and bidisperse mixtures of interacting colloids under the influence of a symmetric flashing periodic substrate. With the addition of dc or ac drives, phase locking, jamming, and new types of ratchet effects occur. In some regimes we find that the addition of a non-ratcheting species increases the velocity of the ratcheting particles. We show that these effects occur due to the collective interactions of the colloids.Comment: 4 pages, 4 postscript figures. Version to appear in Phys. Rev. Let

Relativistic electron-ion recombination in the presence of an intense laser field

Radiative recombination of a relativistic electron with a highly charged ion in the presence of an intense laser field is considered. Various relativistic effects, caused by the high energy of the incoming electron and its strong coupling to the intense laser field, are found to clearly manifest themselves in the spectra of the emitted $\gamma$-photons.Comment: 4 papes, 2 figure

Classical Polylogarithms for Amplitudes and Wilson Loops

We present a compact analytic formula for the two-loop six-particle MHV remainder function (equivalently, the two-loop light-like hexagon Wilson loop) in N = 4 supersymmetric Yang-Mills theory in terms of the classical polylogarithm functions Li_k with cross-ratios of momentum twistor invariants as their arguments. In deriving our result we rely on results from the theory of motives.Comment: 11 pages, v2: journal version, minor corrections and simplifications, additional details available at http://goo.gl/Cl0

Child As Metaphor: Colonialism, Psy-Governance, and Epistemicide

This paper mobilizes transdisciplinary inquiry to explore and deconstruct the often-used comparison of racialized/colonized people, intellectually disabled people and mad people as being like children. To be childlike is a metaphor that is used to denigrate, to classify as irrational and incompetent, to dismiss as not being knowledge holders, to justify governance and action on others’ behalf, to deem as being animistic, as undeveloped, underdeveloped or wrongly developed, and, hence, to subjugate. We explore the political work done by the metaphorical appeal to childhood, and particularly the centrality of the metaphor of childhood to legitimizing colonialism and white supremacy. The article attends to the ways in which this metaphor contributes to the shaping of the material and discursive realities of racialized and colonized others, as well as those who have been psychiatrized and deemed “intellectually disabled”. Further, we explore specific metaphors of child-colony, and child-mad-“crip”. We then detail the developmental logic underlying the historical and continued use of the metaphorics of childhood, and explore how this makes possible an infantilization of colonized peoples and the global South more widely. The material and discursive impact of this metaphor on children’s lives, and particularly children who are racialized, colonized, and/or deemed mad or “crip”, is then considered. We argue that complex adult-child relations, sane-mad relations and Western-majority world relations within global psychiatry, are situated firmly within pejorative notions of what it means to be childlike, and reproduce multi-systemic forms of oppression that, ostensibly in their “best interests”, govern children and all those deemed childlike

Resonant two-photon single ionization of two atoms

Resonant two-photon ionization in a system consisting of two spatially well-separated atoms is studied. Due to two-center electron-electron correlations, the ionization may also proceed through photo-excitation of both atoms with subsequent interatomic Coulombic decay. We show that this channel may dominate the photoionization process and qualitatively change its dependence on the field intensity and the spectra of emitted electrons.Comment: 4 pages, 4 figure