Gravitational uncertainties from dimension-six operators on supersymmetric GUT predictions

We consider the gravity induced dimension six terms in addition to the dimension five terms in the SUSY GUT Lagrangian and find that the prediction for $\alpha_s$ may be washed out completely in supersymmetric grand unified theories unless the triplet higgs mass is smaller than $7\times 10^{16}$ GeV.Comment: 7 pages,latex.Title of original version changed,text added and a figure has been added.Figure is available on request.To appear as a brief Report in Phys.Rev.

Large non-Gaussianity from two-component hybrid inflation

We study the generation of non-Gaussianity in models of hybrid inflation with two inflaton fields, (2-brid inflation). We analyse the region in the parameter and the initial condition space where a large non-Gaussianity may be generated during slow-roll inflation which is generally characterised by a large f_NL, tau_NL and a small g_NL. For certain parameter values we can satisfy tau_NL>>f_NL^2. The bispectrum is of the local type but may have a significant scale dependence. We show that the loop corrections to the power spectrum and bispectrum are suppressed during inflation, if one assume that the fields follow a classical background trajectory. We also include the effect of the waterfall field, which can lead to a significant change in the observables after the waterfall field is destabilised, depending on the couplings between the waterfall and inflaton fields.Comment: 16 pages, 6 figures; v2: comments and references added, typos corrected, matches published versio

A New Dental Superalloy System: V. Embrittling Phase Transformations

The σ phase is rich in Ta. When the Ta concentration is less than 14%, σ does not interfere with the slip mechanism; when the Ta concentration is more than 15%, σ interferes with the slip mechanism. The coherent α-Co 3Ta phase forms at Ta concentrations of less than 15%, whereas incoherent γ-Co 2Ta forms only at higher Ta concentrations. The interface between σ and the matrix is an important factor in the failure mechanism.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67929/2/10.1177_00220345740530013301.pd

Gravitational Smearing of Minimal Supersymmetric Unification Predictions

A short and mean paper.Comment: 10 pages total + 1 postscript figure (included), revised: all lines are TRULY < 70 characters long (try it!); LBL-32905, UCB-PTH-92/3

Phenomenological constraints on SUSY SU(5) GUTs with non-universal gaugino masses

We study phenomenological aspects of supersymmetric SU(5) grand unified theories with non-universal gaugino masses. For large tan beta, we investigate constraints from the requirement of successful electroweak symmetry breaking, the positivity of stau mass squared and the b to s gamma decay rate. In the allowed region, the nature of the lightest supersymmetric particle is determined. Examples of mass spectra are given. We also calculate loop corrections to the bottom mass due to superpartners.Comment: 10 pages, 2 figures (8 eps files), uses REVTeX. Replaced to match the version to be published in PRD: minor corrections and addition

Fermion Masses, Mixing Angles and Supersymmetric SO(10) Unification

We reanalyse the problem of fermion masses in supersymmetric SO(10) grand unified models. In the minimal model, both low energy Higgs doublets belong to the same {\bf{10}} representation of SO(10) implying the unification not only of the gauge but also of the third generation Yukawa couplings. These models predict large values of $\tan\beta \sim 50$. In this paper we study the effects of departing from the minimal conditions in order to see if we can find models with a reduced value of $\tan\beta$. In order to maintain predictability, however, we try to do this with the addition of only one new parameter. We still assume that the fermion masses arise from interactions of the spinor representations with a single ${\bf 10}$ representation, but this ${\bf 10}$ now only contains a part of the two light Higgs doublets. This enables us to introduce one new parameter $\omega=\lambda_b/\lambda_t$. For values of $\omega \ll 1$ we can in principle reduce the value of $\tan\beta$. In fact, $\omega$ is an overall factor which multiplies the down quark and charged lepton Yukawa matrices. Thus the theory is still highly constrained. We show that the first generation quark masses and the CP-violation parameter $\epsilon_K$ yield strong constraints on the phenomenologically allowed models. In the end, we find that large values of $\tan\beta$ are still preferred.Comment: 15 pages, latex, 6 uuencoded figure

On the deflection of asteroids with mirrors

This paper presents an analysis of an asteroid deflection method based on multiple solar concentrators. A model of the deflection through the sublimation of the surface material of an asteroid is presented, with simulation results showing the achievable orbital deflection with, and without, accounting for the effects of mirror contamination due to the ejected debris plume. A second model with simulation results is presented analyzing an enhancement of the Yarkovsky effect, which provides a significant deflection even when the surface temperature is not high enough to sublimate. Finally the dynamical model of solar concentrators in the proximity of an irregular celestial body are discussed, together with a Lyapunov-based controller to maintain the spacecraft concentrators at a required distance from the asteroid

Transcendence over Diversity: black women in the academy

Universities, like many major public institutions have embraced the notion of ‘diversity’ virtually uncritically- it is seen as a moral ‘good in itself’. But what happens to those who come to represent ‘diversity’- the black and minority ethnic groups targeted to increase the institutions thirst for global markets and aversion to accusations of institutional racism? Drawing on existing literature which analyses the process of marginalization in higher education, this paper explores the individual costs to black and female academic staff regardless of the discourse on diversity. However despite the exclusion of staff, black and minority ethnic women are also entering higher education in relatively large numbers as students. Such ‘grassroots’ educational urgency transcends the dominant discourse on diversity and challenges presumptions inherent in top down initiatives such as ‘widening participation’. Such a collective movement from the bottom up shows the importance of understanding black female agency when unpacking the complex dynamics of gendered and racialised exclusion. Black women’s desire for education and learning makes possible a reclaiming of higher education from creeping instrumentalism and reinstates it as a radical site of resistance and refutation

Bottom-Tau Unification in SUSY SU(5) GUT and Constraints from b to s gamma and Muon g-2

An analysis is made on bottom-tau Yukawa unification in supersymmetric (SUSY) SU(5) grand unified theory (GUT) in the framework of minimal supergravity, in which the parameter space is restricted by some experimental constraints including Br(b to s gamma) and muon g-2. The bottom-tau unification can be accommodated to the measured branching ratio Br(b to s gamma) if superparticle masses are relatively heavy and higgsino mass parameter \mu is negative. On the other hand, if we take the latest muon g-2 data to require positive SUSY contributions, then wrong-sign threshold corrections at SUSY scale upset the Yukawa unification with more than 20 percent discrepancy. It has to be compensated by superheavy threshold corrections around the GUT scale, which constrains models of flavor in SUSY GUT. A pattern of the superparticle masses preferred by the three requirements is also commented.Comment: 21pages, 6figure

On Yukawa quasi-unification with mu<0

Although recent data on the muon anomalous magnetic moment strongly disfavor the constrained minimal supersymmetric standard model with mu<0, they cannot exclude it because of theoretical ambiguities. We consider this model supplemented by a Yukawa quasi-unification condition which allows an acceptable b-quark mass. We find that the cosmological upper bound on the lightest sparticle relic abundance is incompatible with the data on the branching ratio of b-->s gamma, which is evaluated by including all the next-to-leading order corrections. Thus, this scheme is not viable.Comment: 4 pages including 3 figures, Revte