2,089 research outputs found
Collapsing Sub-Critical Bubbles
In the standard scenario, the electroweak phase transition is a first order
phase transition which completes by the nucleation of critical bubbles.
Recently, there has been speculation that the standard picture of the
electroweak phase transition is incorrect. Instead, it has been proposed that
throughout the phase transition appreciable amounts of both broken and unbroken
phases of coexist in equilibrium. I argue that this can not be the
case. General principles insure that the universe will remain in a homogenous
state of unbroken until the onset of critical bubble production.Comment: 7 pages plus three figures. OHSTPY-HEP-T-92-016 A topdrawer file of
the figures is appended to the en
The Anomalous Magnetic Moment of the Muon and Higgs-Mediated Flavor Changing Neutral Currents
In the two-Higgs doublet extension of the standard model, flavor-changing
neutral couplings arise naturally. In the lepton sector, the largest such
coupling is expected to be $\mu-\tau-\phi#. We consider the effects of this
coupling on the anomalous magnetic moment of the muon. The resulting bound on
the coupling, unlike previous bounds, is independent of the value of other
unknown couplings. It will be significantly improved by the upcoming E821
experiment at Brookhaven National Lab.Comment: 7 pages Latex, 2 figure
Production, Collection and Utilization of Very Long-Lived Heavy Charged Leptons
If a fourth generation of leptons exists, both the neutrino and its charged
partner must be heavier than 45 GeV. We suppose that the neutrino is the
heavier of the two, and that a global or discrete symmetry prohibits
intergenerational mixing. In that case, non-renormalizable Planck scale
interactions will induce a very small mixing; dimension five interactions will
lead to a lifetime for the heavy charged lepton of years. Production
of such particles is discussed, and it is shown that a few thousands can be
produced and collected at a linear collider. The possible uses of these heavy
leptons is also briefly discussed.Comment: 9 pages Late
Multi-scale Renormalisation Group Improvement of the Effective Potential
Using the renormalisation group and a conjecture concerning the perturbation
series for the effective potential, the leading logarithms in the effective
potential are exactly summed for scalar and Yukawa theories.Comment: 19 pages, DIAS STP 94-09. Expanded to check large N limit, typo's
corrected, to appear in Phys Rev
A typology for clients' multi-project environments
Construction management research and practice is dominated by a single project paradigm. This does not reflect the true nature of many construction clients who have large multi-project portfolios. Traditional single project management strategies are usually adopted for managing such portfolios - with limited success. The literature suggests that programmes, within portfolios, require different forms of management in order to optimize project delivery. In order to better understand these portfolios and thereby allow the exploration of new forms of management, a typology has been developed mapping out the various features of client's construction portfolios. The resultant typology provides a simple method for identifying the programme composition of a portfolio, highlighting the expected features of each programme type, and thereby directing management attention to the main aspects of each programme that can be optimized for efficiency. Six cases of client's construction project portfolios were studied using a highly structured, replication logic, case study methodology. A typology of clients' multi-project environments was developed and validated through literal and theoretical replication between cases. Three main types emerged as descriptive of programmes within client's construction portfolios: bounded programmes, target programmes and rolling programmes. The distinctive features of each type suggest that programme-specific approaches may be necessary for the successful delivery of projects within client's construction portfolios
The appraisal similarity effect: how social appraisals influence liking
The effects of cognitive appraisals on interpersonal relationships have hardly been studied. Three experiments examined how empathic social appraisal could influence liking. We tested for the appraisal similarity effect in which perceived similarity in appraisals boosts liking. In Experiment 1, perception of appraisal similarity led participants to express liking by disclosing personal contact information. This effect was replicated using a selfreport measure of liking in Experiments 2 and 3. Also, by independently manipulating attitude similarity, the appraisal similarity effect was deactivated under perceived attitude dissimilarity. Likewise, the robust attitude similarity effect was invalidated under perceived appraisal dissimilarity. In Experiment 3, the perception of validated personal beliefs mediated this interactive effect in a moderated mediation scenario, and the appraisal similarity effect
First-Principles Calculation of Born Effective Charges and Spontaneous Polarization of Ferroelectric Bismuth Titanate
In this study, we present the results of our first-principles calculations of
the band structure, density of states and the Born effective charge tensors for
the ferroelectric (ground state B1a1) and paraelectric (I4/mmm) phases of
bismuth titanate. The calculations are done using the generalized gradient
approximation (GGA) as well as the local density approximation (LDA) of the
density functional theory. In contrast to the literature, our calculations on
B1a1 structure using GGA and LDA yield smaller indirect band gaps as compared
to the direct band gaps, in agreement with the experimental data. The density
of states shows considerable hybridization among Ti 3d, Bi 6p and O 2p states
indicating covalent nature of the bonds leading to the ferroelectric
instability. The Born effective charge tensors of the constituent ions for the
ground state (B1a1) and paraelectric (I4/mmm) structures were calculated using
the Berry phase method. This is followed by the calculation of the spontaneous
polarization for the ferroelectric B1a1 phase using the Born effective charge
tensors of the individual ions. The calculated value for the spontaneous
polarization of ferroelectric bismuth titanate using different Born effective
charges was found to be in the range of 55+/-13 C/cm2 in comparison to the
reported experimental value of (50+/-10 C/cm2) for single crystals. The
origin of ferroelectricity is attributed to the relatively large displacements
of those oxygen ions in the TiO6 octahedra that lie along the a-axis of the
bismuth titanate crystal.Comment: 36 pages, 5 figure
Fermion and Anti-Fermion Effective Masses in High Temperature Gauge Theories in -Asymmetric Background
We calculate the splitting between fermion and anti-fermion effective masses
in high temperature gauge theories in the presence of a non-vanishing chemical
potential due to the -asymmetric fermionic background. In particular we
consider the case of left-handed leptons in the theory when
the temperature is above GeV and the gauge symmetry is restored.Comment: 13 pages, TIPAC-93001
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