740 research outputs found
The Spectrum of Goldstini and Modulini
When supersymmetry is broken in multiple sectors via independent dynamics,
the theory furnishes a corresponding multiplicity of "goldstini" degrees of
freedom which may play a substantial role in collider phenomenology and
cosmology. In this paper, we explore the tree-level mass spectrum of goldstini
arising from a general admixture of F-term, D-term, and almost no-scale
supersymmetry breaking, employing non-linear superfields and a novel gauge
fixing for supergravity discussed in a companion paper. In theories of F-term
and D-term breaking, goldstini acquire a mass which is precisely twice the
gravitino mass, while the inclusion of no-scale breaking renders one of these
modes, the modulino, massless. We argue that the vanishing modulino mass can be
explained in terms of an accidental and spontaneously broken "global"
supersymmetry.Comment: 10 pages, 2 figures; v2: typo corrected, references updated; v3:
version to appear in JHE
Goldstini
Supersymmetric phenomenology has been largely bound to the hypothesis that
supersymmetry breaking originates from a single source. In this paper, we relax
this underlying assumption and consider a multiplicity of sectors which
independently break supersymmetry, thus yielding a corresponding multiplicity
of goldstini. While one linear combination of goldstini is eaten via the
super-Higgs mechanism, the orthogonal combinations remain in the spectrum as
physical degrees of freedom. Interestingly, supergravity effects induce a
universal tree-level mass for the goldstini which is exactly twice the
gravitino mass. Since visible sector fields can couple dominantly to the
goldstini rather than the gravitino, this framework allows for substantial
departures from conventional supersymmetric phenomenology. In fact, this even
occurs when a conventional mediation scheme is augmented by additional
supersymmetry breaking sectors which are fully sequestered. We discuss a number
of striking collider signatures, including various novel decay modes for the
lightest observable-sector supersymmetric particle, gravitinoless
gauge-mediated spectra, and events with multiple displaced vertices. We also
describe goldstini cosmology and the possibility of goldstini dark matter.Comment: 14 pages, 7 figures; references adde
Polynomial Growth Harmonic Functions on Finitely Generated Abelian Groups
In the present paper, we develop geometric analytic techniques on Cayley
graphs of finitely generated abelian groups to study the polynomial growth
harmonic functions. We develop a geometric analytic proof of the classical
Heilbronn theorem and the recent Nayar theorem on polynomial growth harmonic
functions on lattices \mathds{Z}^n that does not use a representation formula
for harmonic functions. We also calculate the precise dimension of the space of
polynomial growth harmonic functions on finitely generated abelian groups.
While the Cayley graph not only depends on the abelian group, but also on the
choice of a generating set, we find that this dimension depends only on the
group itself.Comment: 15 pages, to appear in Ann. Global Anal. Geo
A Geometric Approach to CP Violation: Applications to the MCPMFV SUSY Model
We analyze the constraints imposed by experimental upper limits on electric
dipole moments (EDMs) within the Maximally CP- and Minimally Flavour-Violating
(MCPMFV) version of the MSSM. Since the MCPMFV scenario has 6 non-standard
CP-violating phases, in addition to the CP-odd QCD vacuum phase \theta_QCD,
cancellations may occur among the CP-violating contributions to the three
measured EDMs, those of the Thallium, neutron and Mercury, leaving open the
possibility of relatively large values of the other CP-violating observables.
We develop a novel geometric method that uses the small-phase approximation as
a starting point, takes the existing EDM constraints into account, and enables
us to find maximal values of other CP-violating observables, such as the EDMs
of the Deuteron and muon, the CP-violating asymmetry in b --> s \gamma decay,
and the B_s mixing phase. We apply this geometric method to provide upper
limits on these observables within specific benchmark supersymmetric scenarios,
including extensions that allow for a non-zero \theta_QCD.Comment: 34 pages, 16 eps figures, to appear in JHE
The Sphaleron Rate in SU(N) Gauge Theory
The sphaleron rate is defined as the diffusion constant for topological
number NCS = int g^2 F Fdual/32 pi^2. It establishes the rate of equilibration
of axial light quark number in QCD and is of interest both in electroweak
baryogenesis and possibly in heavy ion collisions. We calculate the
weak-coupling behavior of the SU(3) sphaleron rate, as well as making the most
sensible extrapolation towards intermediate coupling which we can. We also
study the behavior of the sphaleron rate at weak coupling at large Nc.Comment: 18 pages with 3 figure
Postgraduate education for Chinese medicine practitioners: a Hong Kong perspective
<b>Background</b> Despite Hong Kong government's official commitment to the development of traditional Chinese medicine (TCM) over the last ten years, there appears to have been limited progress in public sector initiated career development and postgraduate training (PGT) for public university trained TCM practitioners. Instead, the private TCM sector is expected to play a major role in nurturing the next generation of TCM practitioners. In the present study we evaluated TCM graduates' perspectives on their career prospects and their views regarding PGT.<p></p>
<b>Method</b> Three focus group discussions with 19 local TCM graduates who had worked full time in a clinical setting for fewer than 5 years. <p></p>
<b>Results</b> Graduates were generally uncertain about how to develop their career pathways in Hong Kong with few postgraduate development opportunities; because of this some were planning to leave the profession altogether. Despite their expressed needs, they were dissatisfied with the current quality of local PGT and suggested various ways for improvement including supervised practice-based learning, competency-based training, and accreditation of training with trainee involvement in design and evaluation. In addition they identified educational needs beyond TCM, in particular a better understanding of western medicine and team working so that primary care provision might be more integrated in the future. <p></p>
<b>Conclusion</b> TCM graduates in Hong Kong feel let down by the lack of public PGT opportunities which is hindering career development. To develop a new generation of TCM practitioners with the capacity to provide quality and comprehensive care, a stronger role for the government, including sufficient public funding, in promoting TCM graduates' careers and training development is suggested. Recent British and Australian experiences in prevocational western medicine training reform may serve as a source of references when relevant program for TCM graduates is planned in the futur
Global institutions and local filtering: Introducing independent directors to Taiwanese corporate boards
Drawing on the idea of selective interaction between organizations and environments, the authors examine how organizations change their traditional practices when they are exposed to new institutional environments. In the context of corporate governance change in response to financial market globalization, they argue that global institutional influence is moderated by local corporate control contexts that function as filtering mechanisms. The authors empirically analyse the adoption of a new corporate governance practice, i.e., the initial introduction of independent directors, in Taiwanese public firms, where family governance has been a dominant governance model. The findings suggest that while firms exposed to US capital markets are more likely to adopt independent directors, this facilitating effect weakens when the firms are under strong family control and is amplified when they are unbound from local frameworks through the key leader???s education or their geographic context
Flavoured soft leptogenesis and natural values of the B term
We revisit flavour effects in soft leptogenesis relaxing the assumption of
universality for the soft supersymmetry breaking terms. We find that with
respect to the case in which the heavy sneutrinos decay with equal rates and
equal CP asymmetries for all lepton flavours, hierarchical flavour
configurations can enhance the efficiency by more than two orders of magnitude.
This translates in more than three order of magnitude with respect to the
one-flavour approximation. We verify that lepton flavour equilibration effects
related to off-diagonal soft slepton masses are ineffective for damping these
large enhancements. We show that soft leptogenesis can be successful for
unusual values of the relevant parameters, allowing for and for values of the washout parameter up to .Comment: 23 pages, 5 figures postscript, Minor changes to match the published
version in JHE
Diffractive Higgs Production by AdS Pomeron Fusion
The double diffractive Higgs production at central rapidity is formulated in
terms of the fusion of two AdS gravitons/Pomerons first introduced by Brower,
Polchinski, Strassler and Tan in elastic scattering. Here we propose a simple
self-consistent holographic framework capable of providing phenomenologically
compelling estimates of diffractive cross sections at the LHC. As in the
traditional weak coupling approach, we anticipate that several phenomenological
parameters must be tested and calibrated through factorization for a
self-consistent description of other diffractive process such as total cross
sections, deep inelastic scattering and heavy quark production in the central
region.Comment: 53 pages, 8 figure
Down regulation of E-Cadherin (ECAD) - a predictor for occult metastatic disease in sentinel node biopsy of early squamous cell carcinomas of the oral cavity and oropharynx
<p>Abstract</p> <p>Background</p> <p>Prognostic factors in predicting occult lymph node metastasis in patients with head and neck squamous-cell carcinoma (HNSCC) are necessary to improve the results of the sentinel lymph node procedure in this tumour type. The E-Cadherin glycoprotein is an intercellular adhesion molecule in epithelial cells, which plays an important role in establishing and maintaining intercellular connections.</p> <p>Objectives</p> <p>To determine the value of the molecular marker E-Cadherin in predicting regional metastatic disease.</p> <p>Methods</p> <p>E-Cadherin expression in tumour tissue of 120 patients with HNSCC of the oral cavity and oropharynx were evaluated using the tissue microarray technique. 110 tumours were located in the oral cavity (91.7%; mostly tongue), 10 tumours in the oropharynx (8.3%). Intensity of E-Cadherin expression was quantified by the Intensity Reactivity Score (IRS). These results were correlated with the lymph node status of biopsied sentinel lymph nodes. Univariate and multivariate analysis was used to determine statistical significance.</p> <p>Results</p> <p>pT-stage, gender, tumour side and location did not correlate with lymph node metastasis. Differentiation grade (<it>p </it>= 0.018) and down regulation of E-Cadherin expression significantly correlate with positive lymph node status (<it>p </it>= 0.005) in univariate and multivariate analysis.</p> <p>Conclusion</p> <p>These data suggest that loss of E-cadherin expression is associated with increased lymhogeneous metastasis of HNSCC. E-cadherin immunohistochemistry may be used as a predictor for lymph node metastasis in squamous cell carcinoma of the oral cavity and oropharynx.</p> <p><b>Level of evidence: 2b</b></p
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