2,864 research outputs found
Inertial Spontaneous Symmetry Breaking and Quantum Scale Invariance
Weyl invariant theories of scalars and gravity can generate all mass scales
spontaneously, initiated by a dynamical process of "inertial spontaneous
symmetry breaking" that does not involve a potential. This is dictated by the
structure of the Weyl current, , and a cosmological phase during which
the universe expands and the Einstein-Hilbert effective action is formed.
Maintaining exact Weyl invariance in the renormalised quantum theory is
straightforward when renormalisation conditions are referred back to the VEV's
of fields in the action of the theory, which implies a conserved Weyl current.
We do not require scale invariant regulators. We illustrate the computation of
a Weyl invariant Coleman-Weinberg potential
Beyond the Standard Model
The attempts to develop models beyond the Standard Model are briefly reviewed paying particular regard to the mechanisms responsible for symmetry breaking and mass generation. A comparison is made of the theoretical expectations with recent precision measurements for theories with composite Higgs and for supersymmetric theories with elementary Higgs boson(s). The implications of a heavy top quark and the origin of the light quark and lepton masses and mixing angles are considered within these frameworks
Hybrid Natural Inflation
We construct two simple effective field theory versions of {\it Hybrid
Natural Inflation (HNI)} that illustrate the range of its phenomenological
implications. The resulting inflationary sector potential,
, arises naturally, with the inflaton field a
pseudo-Nambu-Goldstone boson. The end of inflation is triggered by a waterfall
field and the conditions for this to happen are determined. Also of interest is
the fact that the slow-roll parameter (and hence the tensor ) is
a non-monotonic function of the field with a maximum where observables take
universal values that determines the maximum possible tensor to scalar ratio
. In one of the models the inflationary scale can be as low as the
electroweak scale. We explore in detail the associated HNI phenomenology,
taking account of the constraints from Black Hole production, and perform a
detailed fit to the Planck 2015 temperature and polarisation data.Comment: V2: 19 pages, 2 figures, 1 table. Extended discussions and new
references added. Version accepted for publication in JHE
Infra-red fixed point structure of soft supersymmetry breaking mass terms
We show that the soft SUSY breaking mass terms may have infra-red stable fixed points at which they are related to the gaugino masses and argue that in a generic unification these masses should lie close to their fixed points. We consider the implications for the family dependence of squark and slepton masses and the related flavour changing neutral currents and determine conditions under which models with flavour changing couplings and masses at a high scale may lead to a family independent effective theory at low scales. The analysis is illustrated for a variety of models for which we compute both the fixed point structure and determine the rate of approach to the fixed point.We show that the soft SUSY breaking mass terms may have infra-red stable fixed points at which they are related to the gaugino masses and argue that in a generic unification these masses should lie close to their fixed points. We consider the implications for the family dependence of squark and slepton masses and the related flavour changing neutral currents and determine conditions under which models with flavour changing couplings and masses at a high scale may lead to a family independent effective theory at low scales. The analysis is illustrated for a variety of models for which we compute both the fixed point structure and determine the rate of approach to the fixed point
Probing the Structure of the Pomeron
We suggest that the pseudo-rapidity cut dependence of diffractive deep-inelastic scattering events at HERA may provide a sensitive test of models of diffraction. A comparison with the experimental cross section shows that the Donnachie-Landshoff model and a simple two-gluon exchange model of the pomeron model are disfavoured. However a model with a direct coupling of the pomeron to quarks is viable for a harder quark--pomeron form factor, as is a model based on the leading-twist operator contribution. We also consider a direct-coupling scalar pomeron model. We comment on the implications of these results for the determination of the partonic structure of the pomeron.We suggest that the pseudo-rapidity cut dependence of diffractive deep-inelastic scattering events at HERA may provide a sensitive test of models of diffraction. A comparison with the experimental cross section shows that the Donnachie-Landshoff model and a simple two-gluon exchange model of the pomeron model are disfavoured. However a model with a direct coupling of the pomeron to quarks is viable for a harder quark--pomeron form factor, as is a model based on the leading-twist operator contribution. We also consider a direct-coupling scalar pomeron model. We comment on the implications of these results for the determination of the partonic structure of the pomeron
Precision test of a Fermion mass texture
Texture zeros in the quark Yukawa matrices generally lead to precise and simple expressions for CKM matrix elements in terms of ratios of quark masses. Using the new data on decays we test a particularly promising texture zero solution and show that it is at best approximate. We analyse the approximate texture zero structure and show it is consistent with experiment. We investigate the implications for the CKM unitarity triangle, measurements at and as well as for the theories which invoke family symmetries
Dissemination and implementation science training needs: Insights from practitioners and researchers
INTRODUCTION: Dissemination and implementation research training has great potential to improve the impact and reach of health-related research; however, research training needs from the end user perspective are unknown. This paper identifies and prioritizes dissemination and implementation research training needs. METHODS: A diverse sample of researchers, practitioners, and policymakers was invited to participate in Concept Mapping in 2014–2015. Phase 1 (Brainstorming) gathered participants' responses to the prompt: To improve the impact of research evidence in practice and policy settings, a skill in which researchers need more training is… The resulting statement list was edited and included subsequent phases. Phase 2 (Sorting) asked participants to sort each statement into conceptual piles. In Phase 3 (Rating), participants rated the difficulty and importance of incorporating each statement into a training curriculum. A multidisciplinary team synthesized and interpreted the results in 2015–2016. RESULTS: During Brainstorming, 60 researchers and 60 practitioners/policymakers contributed 274 unique statements. Twenty-nine researchers and 16 practitioners completed sorting and rating. Nine concept clusters were identified: Communicating Research Findings, Improve Practice Partnerships, Make Research More Relevant, Strengthen Communication Skills, Develop Research Methods and Measures, Consider and Enhance Fit, Build Capacity for Research, and Understand Multilevel Context. Though researchers and practitioners had high agreement about importance (r =0.93) and difficulty (r =0.80), ratings differed for several clusters (e.g., Build Capacity for Research). CONCLUSIONS: Including researcher and practitioner perspectives in competency development for dissemination and implementation research identifies skills and capacities needed to conduct and communicate contextualized, meaningful, and relevant research
Carbon Dioxide Injection for Hypervelocity Boundary Layer Stability
An approach for introducing carbon dioxide as a means or stabilizing a hypervelocity boundary layer over a slender bodied vehicle is investigated through the use of numerical simulations. In the current study, two different test bodies are examined. The first is a five-degree-half-angle cone currently under research at the GALCIT T5 Shock Tunnel with a 4 cm porous wall insert used to transpire gas into the boundary layer. The second test body is a similar cone with a porous wall over a majority of cone surface. Computationally, the transpiration is performed using an axi-symmetric flow simulation with wall-normal blowing. The effect of the injection and the transition location are gauged by solving the parabolized stability equations and using the semi-empirical e^N method. The results show transition due to the injection for the first test body and a delay in the transition location for the second test body as compared to a cone without injection under the same flight conditions. The mechanism for the stabilizing effect of carbon dioxide is also explored through selectively applying non-equilibrium processes to the stability analysis. The results show that vibrational non-equilibrium plays a role in reducing disturbance amplification; however, other factors also contribute
The kaon nucleon interaction
The K-matrix formalism for the low energy KN interaction is reviewed. By using the N/D method to compute the scattering matrix for left hand singularities chosen to approximate the physical singularities of the KN and ΣΤ amplitudes the nature of the energy dependence of the inverse K-matrix elements are investigated. From this it is concluded that an effective range parameterisation should be a good approximation to the inverse K-matrix elements and that the off diagonal elements of the effective range matrix may not, ά priori, be neglected. The application of dispersion relations to the prediction of the strange particle coupling constants is discussed. A once subtracted sum rule is introduced which reduces the discrepancy in the prediction of the coupling constants due to the use of different low energy parameterisations for the KN amplitude. The resultant prediction of the coupling constants is incompatible with the SU(3) predictions. A new S-wave zero range fit to the low energy KN data is performed. A good fit is obtained which improves on previous analyses over the low energy KN region. The values of the coupling constants predicted by the standard dispersion relation using this parameterisation are again incompatible with the SU(3) predictions. Finally the effect of the non-negligible P waves in the isospin one channel are investigated using a constant scattering length parameterisation for these waves in the analysis of the low energy KN data
Beyond MFV in family symmetry theories of fermion masses
Minimal Flavour Violation (MFV) postulates that the only source of flavour
changing neutral currents and CP violation, as in the Standard Model, is the
CKM matrix. However it does not address the origin of fermion masses and mixing
and models that do usually have a structure that goes well beyond the MFV
framework. In this paper we compare the MFV predictions with those obtained in
models based on spontaneously broken (horizontal) family symmetries, both
Abelian and non-Abelian. The generic suppression of flavour changing processes
in these models turns out to be weaker than in the MFV hypothesis. Despite
this, in the supersymmetric case, the suppression may still be consistent with
a solution to the hierarchy problem, with masses of superpartners below 1 TeV.
A comparison of FCNC and CP violation in processes involving a variety of
different family quantum numbers should be able to distinguish between various
family symmetry models and models satisfying the MFV hypothesis.Comment: 34 pages, no figure
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