Cosmological Higgs fields

We present a time-dependent solution to the coupled Einstein-Higgs equations for general Higgs-type potentials in the context of flat FRW cosmological models. Possible implications are discussed.Comment: 5 pages, no figures. Version to be published in Phys. Rev. Lett. Changes: references and citations added; introduction partly modified; expanded discussion of relations between parameters in the Higgs potentia

Topological Defects as Seeds for Eternal Inflation

We investigate the global structure of inflationary universe both by analytical methods and by computer simulations of stochastic processes in the early Universe. We show that the global structure of the universe depends crucially on the mechanism of inflation. In the simplest models of chaotic inflation the Universe looks like a sea of thermalized phase surrounding permanently self-reproducing inflationary domains. In the theories where inflation occurs near a local extremum of the effective potential corresponding to a metastable state, the Universe looks like de Sitter space surrounding islands of thermalized phase. A similar picture appears even if the state $\phi = 0$ is unstable but the effective potential has a discrete symmetry $\phi \to =-\phi$. In this case the Universe becomes divided into domains containing different phases. These domains will be separated from each other by domain walls. However, unlike ordinary domain walls, these domain walls will inflate, and their thickness will exponentially grow. In the theories with continuous symmetries inflation generates exponentially expanding strings and monopoles surrounded by thermalized phase. Inflating topological defects will be stable, and they will unceasingly produce new inflating topological defects. This means that topological defects may play a role of indestructible seeds for eternal inflation.Comment: 21 pages, 17 figures (not included), Stanford University preprint SU--ITP--94--

Creation of a Compact Topologically Nontrivial Inflationary Universe

If inflation can occur only at the energy density V much smaller than the Planck density, which is the case for many inflationary models based on string theory, then the probability of quantum creation of a closed or an infinitely large open inflationary universe is exponentially suppressed for all known choices of the wave function of the universe. Meanwhile under certain conditions there is no exponential suppression for creation of topologically nontrivial compact flat or open inflationary universes. This suggests, contrary to the standard textbook lore, that compact flat or open universes with nontrivial topology should be considered a rule rather than an exception.Comment: 9 pages 2 figures, new materials and references adde

Supersymmetric hybrid inflation in the braneworld scenario

In this paper we reconsider the supersymmetric hybrid inflation in the context of the braneworld scenario . The observational bounds are satisfied with an inflationary energy scale $\mu\simeq 4\times 10^{-4}M_p$, without any fine-tuning of the coupling parameter, provided that the five-dimensional Planck scale is $M_5\stackrel{<}{\sim} 2\times 10^{-3}M_p$ . We have also obtained an upper bound on the the brane tension .Comment: 8 pages (Latex

Inflation with Ω≠1\Omega \not = 1

We discuss various models of inflationary universe with $\Omega \not = 1$. A homogeneous universe with $\Omega > 1$ may appear due to creation of the universe "from nothing" in the theories where the effective potential becomes very steep at large $\phi$, or in the theories where the inflaton field $\phi$ nonminimally couples to gravity. Inflation with $\Omega < 1$ generally requires intermediate first order phase transition with the bubble formation, and with a second stage of inflation inside the bubble. It is possible to realize this scenario in the context of a theory of one scalar field, but typically it requires artificially bent effective potentials and/or nonminimal kinetic terms. It is much easier to obtain an open universe in the models involving two scalar fields. However, these models have their own specific problems. We propose three different models of this type which can describe an open homogeneous inflationary universe.Comment: 29 pages, LaTeX, parameters of one of the models are slightly modifie

False Vacuum Inflation with a Quartic Potential

We consider a variant of Hybrid Inflation, where inflation is driven by two interacting scalar fields, one of which has a `Mexican hat' potential and the other a quartic potential. Given the appropriate initial conditions one of the fields can be trapped in a false vacuum state, supported by couplings to the other field. The energy of this vacuum can be used to drive inflation, which ends when the vacuum decays to one of its true minima. Depending on parameters, it is possible for inflation to proceed via two separate epochs, with the potential temporarily steepening sufficiently to suspend inflation. We use numerical simulations to analyse the possibilities, and emphasise the shortcomings of the slow-roll approximation for analysing this scenario. We also calculate the density perturbations produced, which can have a spectral index greater than one.Comment: 10 pages, RevTeX 3.0, no figure

From satisfaction to expectation: The patient's perspective in lower limb prosthetic care

Neck pain is a common musculoskeletal complaint and a relationship with reduced work-related functional capacity is assumed. A validated instrument to test functional capacity of patients with neck pain is unavailable. The objective of this study was to develop a Functional Capacity Evaluation (FCE), which is content valid for determining functional capacity in patients with work related neck disorders (WRND). A review of epidemiological review literature was conducted to identify physical risk factors for WRND. Evidence was found that physical risk factors contribute in development of WRND. Physical risk factors were related to repetitive movements, forceful movements, awkward positions and static contractions of the neck or the neck/shoulder region. An FCE was designed based on the risk factors identified. Eight tests were selected to cover all risk factors: repetitive side reaching, repetitive reaching overhead, static overhead work, front carry, forward static bend neck, overhead lift and the neck strength test. Content validity of this FCE was established by providing the rationale, specific objectives and operational definitions of the FCE. Further research is needed to establish reliability and other aspects of validity of the neck-FCE Aim Worldwide, family- centred and co- ordinated care are seen as the two most desirable and effective methods of paediatric care delivery. This study outlines current views on how team collaboration comprising professionals in paediatric rehabilitation and special education and the parents of children with disabilities should be organized, and analyses the policies of five paediatric rehabilitation settings associated with the care of 44 children with cerebral palsy ( CP) in the Netherlands. Methods For an overview of current ideas on collaboration, written statements of professional associations in Dutch paediatric rehabilitation were examined. The policy statements of the five participating settings were derived from their institutional files. Documents detailing the collaborative arrangements involving the various professionals and parents were evaluated at the institutional level and at the child level. Involvement of the stakeholders was analysed based on team conferences. Results Also in the Netherlands collaboration between rehabilitation and education professionals and parents is endorsed as the key principle in paediatric rehabilitation, with at its core the team conference in which the various priorities and goals are formulated and integrated into a personalized treatment plan. As to their collaborative approaches between rehabilitation centre and school, the five paediatric settings rarely differed, but at the child level approaches varied. Teams were large ( averaging 10.5 members), and all three stakeholder groups were represented, but involvement differed per setting, as did the roles and contributions of the individual team members. Conclusion Collaboration between rehabilitation and education professionals and parents is supported and encouraged nationwide. Views on collaboration have been formulated, and general guidelines on family- centred and co- ordinated care are available. Yet, collaborative practices in Dutch paediatric care are still developing. Protocols that carefully delineate the commitments to collaborate and that translate the policies into practical, detailed guidelines are needed, as they are a prerequisite for successful teamwork

Predictability crisis in inflationary cosmology and its resolution

Models of inflationary cosmology can lead to variation of observable parameters ("constants of Nature") on extremely large scales. The question of making probabilistic predictions for today's observables in such models has been investigated in the literature. Because of the infinite thermalized volume resulting from eternal inflation, it has proven difficult to obtain a meaningful and unambiguous probability distribution for observables, in particular due to the gauge dependence. In the present paper, we further develop the gauge-invariant procedure proposed in a previous work for models with a continuous variation of "constants". The recipe uses an unbiased selection of a connected piece of the thermalized volume as sample for the probability distribution. To implement the procedure numerically, we develop two methods applicable to a reasonably wide class of models: one based on the Fokker-Planck equation of stochastic inflation, and the other based on direct simulation of inflationary spacetime. We present and compare results obtained using these methods.Comment: 23 pages, 13 figure

Comment on Octet Baryon Magnetic Moments in the Chiral Quark Model with Configuration Mixing

The importance of exchange currents, and of conserving isotopic spin at both the quark and baryon levels in application of the chiral quark model to any calculation of baryon magnetic moments is emphasized.Comment: 5 pages, Latex fil