Pure Gravity Mediation and Spontaneous B-L Breaking from Strong Dynamics

In pure gravity mediation (PGM), the most minimal scheme for the mediation of supersymmetry (SUSY) breaking to the visible sector, soft masses for the standard model gauginos are generated at one loop rather than via direct couplings to the SUSY-breaking field. In any concrete implementation of PGM, the SUSY-breaking field is therefore required to carry nonzero charge under some global or local symmetry. As we point out in this note, a prime candidate for such a symmetry might be B-L, the Abelian gauge symmetry associated with the difference between baryon number B and lepton number L. The F-term of the SUSY-breaking field then not only breaks SUSY, but also B-L, which relates the respective spontaneous breaking of SUSY and B-L at a fundamental level. As a particularly interesting consequence, we find that the heavy Majorana neutrino mass scale ends up being tied to the gravitino mass, Lambda_N ~ m_3/2. Assuming nonthermal leptogenesis to be responsible for the generation of the baryon asymmetry of the universe, this connection may then explain why SUSY necessarily needs to be broken at a rather high energy scale, so that m_3/2 >~ 1000 TeV in accord with the concept of PGM. We illustrate our idea by means of a minimal model of dynamical SUSY breaking, in which B-L is identified as a weakly gauged flavor symmetry. We also discuss the effect of the B-L gauge dynamics on the superparticle mass spectrum as well as the resulting constraints on the parameter space of our model. In particular, we comment on the role of the B-L D-term.Comment: 25 pages, 1 figur

Nano-composite single grain YBa2Cu3O 7-δ/Y2Ba4CuBiOy bulk superconductors

We have succeeded recently in synthesizing a chemically stable, inert family of materials of composition Y2Ba4CuMOy (Y-2411 where M Nb, Ta, Mo, W, Zr, Hf) within the superconducting YBa 2Cu3O7-δ (Y-123) phase matrix that forms effective flux pinning centers of nano-scale dimensions. In this paper we report the synthesis of the Y2Ba4CuBiOy phase with nano-scale dimensions that is similarly compatible with the Y-123 matrix and which does not impair the properties of the bulk superconductor. YBa 2Cu3O7-δ/Y2BaCuO5 (Y-123/Y-211) precursor powders enriched with various amounts of Bi 2O3 and Y2Ba4CuBiOy have been fabricated successfully in the form of large, single grains by the top seeded melt growth (TSMG) process. Microstructural studies of these composites reveal the presence of nanometer-sized Y2Ba4CuBiO y and much larger Y-211 phase particles (∼1 νm) embedded in the Y-123 phase matrix. The critical current density of the nano-composites is observed to increase significantly compared to undoped YBCO. © 2006 IOP Publishing Ltd

Collective treatment of High Energy Thresholds in SUSY - GUTs

Supersymmetric GUTs are the most natural extension of the Standard model unifying electroweak and strong forces. Despite their indubitable virtues, among these the gauge coupling unification and the quantization of the electric charge, one of their shortcomings is the large number of parameters used to describe the high energy thresholds (HET), which are hard to handle. We present a new method according to which the effects of the HET, in any GUT model, can be described by fewer parameters that are randomly produced from the original set of the parameters of the model. In this way, regions favoured by the experimental data are easier to locate, avoiding a detailed and time consuming exploration of the parameter space, which is multidimensional even in the most economic unifying schemes. To check the efficiency of this method, we directly apply it to a SUSY SO(10) GUT model in which the doublet-triplet splitting is realized through the Dimopoulos-Wilczek mechanism. We show that the demand of gauge coupling unification, in conjunction with precision data, locates regions of the parameter space in which values of the strong coupling \astrong are within the experimental limits, along with a suppressed nucleon decay, mediated by a higgsino driven dimension five operators, yielding lifetimes that are comfortably above the current experimental bounds. These regions open up for values of the SUSY breaking parameters m_0, M_1/2 < 1 TeV being therefore accessible to LHC.Comment: 21 pages, 8 figures, UA-NPPS/BSM-10/02 (added

An Automatic Invisible Axion In The SUSY Preon Model

It is shown that the recently proposed preon model which provides a unified origin of the diverse mass scale and an explanation of family replication as well as of inter-family mass-hierarchy, possesses a Peccei-Quinn symmetry whose spontaneous breaking leads to an automatic invisible axion. Existence of the PQ-symmetry is simply a consequence of supersymmetry and requirement of minimality in the field-content and interactions, which propose that the lagrangian should possess only those terms which are dictated by the gauge principle and no others. In addition to the axion, the model also generates two superlight Goldstone bosons and their superpartners which are cosmologically safe.Comment: (TeX file) 16 Page

A Study on Brain Abscess

INTRODUCTION: Brain abscess is defined as a focal, intra cerebral infection that begins as a localized area of cerebritis and develops into a collection of pus surrounded by a well-vascularized capsule. Although rare in developed countries brain abscess still remains a significant health care problem in developing countries. Historically brain abscess was mentioned by Hippocrates in 460 BC and he himself has described the association of brain abscess with ear infection. The Brain is well protected from infections by a thick skull vault, tough duramater and important barriers like bloodbrain barrier and blood cerebrospinal fluid (CSF) barrier. A breach in any of these barriers leads to entry of microorganisms into the brain initiating a suppurative inflammation culminating in brain abscess. The inciting organism can be introduced from outside by trauma or endogenously from infection in a contiguous site eg. ear or occasionally blood borne, heart disease and systemic infection. Although the portal of entry of the organism is commonly identified, the organism remains obscure in 10 -37% of the patients. In the recent decades the addition of Computed tomography (CT) and Magnetic Resonance Imaging (MRI) to the diagnostic armamentarium has facilitated early identification and thereby prompt institution of therapy in brain abscess. Improved microbiological techniques have increased the appreciation of the bacteriological spectrum of brain abscess especially anaerobes. The advanced surgical techniques viz. stereotactic guided aspiration, real-time ultrasound imaging has caused a paradigm shift in the management and outcome of brain abscess. AIM OF THE STUDY: The aim is to study the epidemiology, clinical profile, management and outcome in patients with brain abscess. MATERIALS AND METHODS: All patients admitted in the Institute of Neurology, Rajiv Gandhi Government General Hospital & Madras Medical College, Chennai, between August 2010 and February 2013, with brain abscess was included in this study. Inclusion Criteria: All patients who have been diagnosed as having brain abscess were included in the study group. On admission patient’s clinical profile such as age, sex, presenting symptoms complete neurological examination, conscious level and signs were recorded. All patients were subjected to CT scan brain plain study. In CT of patients having brain abscess the following features were noted – location, number of abscess, loculation, associated hydrocephalus. Patients were either managed conservatively or by surgery. The specimen obtained by surgical means was subjected to microbiological study. All the data were entered in a proforma as shown in the appendix. Outcome analysis was done at the time of discharge. CONCLUSION: A study of 60 patients presenting with brain abscess has lead to the following conclusions. 1. Brain abscess still occurs in the modern era, better visualized with modern imaging studies. 2. Retro viral infections also contribute for brain abscess apart from other known causes, hence all cases of brain abscesses to be screened for retro viral infection. 3. Neonates and children show poor prognosis and prompt aggressive management is essential for better outcome. 4. Constant vigil and surveillance will help for decreasing the magnitude of morbidity and mortality from brain abscess

Recent direct measurement of the Top quark mass and quasi-infrared fixed point

We note that the recent direct measurement of the top quark mass at $173.3 \pm 5.6 (stat) \pm 6.2 (syst)$ by D0 collaboration severely constrains the theoretically attractive infra-red fixed point scenario of the top quark Yukawa coupling in supersymmetric GUTs. For one-step unified models the above mentioned measurement bounds the arbitrary but experimentally determinable parameter $\tan \beta$ to the range $1.3 \le \tan \beta \le 2.1$. Further crunch on the top quark mass may determine $\tan \beta$ even more accurately within the fixed point scenario. On the other hand an experimental value of $\tan \beta > 2.1$ will rule out the fixed point scenario bounding $h^2_t(M_X)/4 \pi$ to 0.022 from above.Comment: 7 pages, Latex with epsf style, 1 figure, captions.st

New Lepton Family Symmetry and Neutrino Tribimaximal Mixing

The newly proposed finite symmetry Sigma(81) is applied to the problem of neutrino tribimaximal mixing. The result is more satisfactory than those of previous models based on A_4 in that the use of auxiliary symmetries (or mechanisms) may be avoided. Deviations from the tribimaximal pattern are expected, but because of its basic structure, only tan^2 (theta_12) may differ significantly from 0.5 (say 0.45) with sin^2 (2 theta_23) remaining very close to one, and theta_13 very nearly zero.Comment: 8 pages, no figur