2,169 research outputs found
Age, Life-Satisfaction, and Relative Income: Insights from the UK and Germany
We first confirm previous results with the German Socio-Economic Panel by Layard et al. (2010), and obtain strong negative effects of comparison income. However, when we split the sample by age, we find quite different results for reference income. The effects on life-satisfaction are positive and significant for those under 45, consistent with Hirschman's (1973) 'tunnel effect', and only negative (and larger than in the full sample) for those over 45, when relative deprivation dominates. Thus for young respondents, reference income's signalling role, indicating potential future prospects, can outweigh relative deprivation effects. Own-income effects are also larger for the older sample, and of greater magnitude than the comparison income effect. In East Germany the reference income effects are insignificant for all. With data from the British Household Panel Survey, we confirm standard results when encompassing all ages, but reference income loses significance in both age groups, and most surprisingly, even own income becomes insignificant for those over 45, while education has significant negative effects.subjective life-satisfaction, comparison income, reference groups, age, welfare
The Cosmic Microwave Background and the Stellar Initial Mass Function
We argue that an increased temperature in star-forming clouds alters the
stellar initial mass function to be more bottom-light than in the Milky Way. At
redshifts , heating from the cosmic microwave background radiation
produces this effect in all galaxies, and it is also present at lower redshifts
in galaxies with very high star formation rates (SFRs). A failure to account
for it means that at present, photometric template fitting likely overestimates
stellar masses and star formation rates for the highest-redshift and
highest-SFR galaxies. In addition this may resolve several outstanding problems
in the chemical evolution of galactic halos.Comment: 9 pages, 5 figures. Published in MNRAS. Added further reference
Angular Inflation from Supergravity
We study supergravity inflationary models where inflation is produced along
the angular direction. For this we express the scalar component of a chiral
superfield in terms of the radial and the angular components. We then express
the supergravity potential in a form particularly simple for calculations
involving polynomial expressions for the superpotential and Kahler potential.
We show for a simple Polonyi model the angular direction may give rise to a
stage of inflation when the radial field is fixed to its minimum. We obtain
analytical expressions for all the relevant inflationary quantities and discuss
the possibility of supersymmetry breaking in the radial direction while
inflating by the angular component.Comment: 7 pages, one figure. Final version. Title changed, two figures
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Where in the String Landscape is Quintessence
We argue that quintessence may reside in certain corners of the string
landscape. It arises as a linear combination of internal space components of
higher rank forms, which are axion-like at low energies, and may mix with
4-forms after compactification of the Chern-Simons terms to 4D due to internal
space fluxes. The mixing induces an effective mass term, with an action which
{\it preserves} the axion shift symmetry, breaking it spontaneously after the
background selection. With several axions, several 4-forms, and a low string
scale, as in one of the setups already invoked for dynamically explaining a
tiny residual vacuum energy in string theory, the 4D mass matrix generated by
random fluxes may have ultralight eigenmodes over the landscape, which are
quintessence. We illustrate how this works in simplest cases, and outline how
to get the lightest mass to be comparable to the Hubble scale now, . The shift symmetry protects the smallest mass from
perturbative corrections in field theory. Further, if the ultralight eigenmode
does not couple directly to any sector strongly coupled at a high scale, the
non-perturbative field theory corrections to its potential will also be
suppressed. Finally, if the compactification length is larger than the string
length by more than an order of magnitude, the gravitational corrections may
remain small too, even when the field value approaches .Comment: 8 pages RevTeX; added references, matches published versio
The cosmic gravitational wave background in a cyclic universe
Inflation predicts a primordial gravitational wave spectrum that is slightly
``red,'' i.e., nearly scale-invariant with slowly increasing power at longer
wavelengths. In this paper, we compute both the amplitude and spectral form of
the primordial tensor spectrum predicted by cyclic/ekpyrotic models. The
spectrum is blue and exponentially suppressed compared to inflation on long
wavelengths. The strongest observational constraint emerges from the
requirement that the energy density in gravitational waves should not exceed
around 10 per cent of the energy density at the time of nucleosynthesis.Comment: 4 pages, 3 figuer
The mystery of the cosmic vacuum energy density and the accelerated expansion of the Universe
After a short history of the -term it is explained why the
(effective) cosmological constant is expected to obtain contributions from
short-distance-physics, corresponding to an energy scale of at least 100 GeV.
The actual tiny value of the cosmological constant in any natural scale of
units represents, therefore, one of the deepest mysteries of present day
fundamental physics. We also briefly discuss recent astronomical evidence for a
cosmologically significant vacuum energy density causing an accelerating
expansion of the universe. This arises mainly from the Hubble diagram of type
Ia supernovae and from the observed temperature fluctuations of the cosmic
microwave background radiation. If this should become an established fact, we
are also confronted with a disturbing {\it cosmic coincidence} problem.Comment: 12 pages, 2 figures, iopart macros include
So Far so Good: Age, Happiness, and Relative Income
In a simple 2-period model of relative income under uncertainty, higher comparison income for the younger cohort can signal higher or lower expected lifetime relative income, and hence either increase or decrease well-being. With data from the German Socio-Economic Panel and the British Household Panel Survey, we first confirm the standard negative effects of comparison income on life satisfaction with all age groups, and many controls. However when we split the West German sample by age we find a positive significant effect of comparison income in the under 45s, and the usual negative effect only in the over 45 group. With the same split in UK and East German data, comparison income loses significance, which is consistent with the model prediction for the younger group. Our results provide first evidence that the standard aggregation with only a quadratic control for age can obscure major differences in the effects of relative income.Subjective life-satisfaction, comparison income, reference groups, age, welfare
Visible Branes with Negative Tension in Heterotic M-Theory
It is shown that there exist large classes of BPS vacua in heterotic M-theory
which have negative tension on the visible orbifold plane, positive tension on
the hidden plane and positive tension, physical five-branes in the bulk space.
Explicit examples of such vacua are presented. Furthermore, it is demonstrated
that the ratio, beta/|alpha|, of the bulk five-brane tension to the visible
plane tension can, for several large classes of such vacua, be made arbitrarily
small. Hence, it is straightforward to find vacua with the properties required
in the examples of the Ekpyrotic theory of cosmology - a visible brane with
negative tension and beta/|alpha| small. This contradicts recent claims in the
literature.Comment: 30 page
Dynamical vacuum energy, holographic quintom, and the reconstruction of scalar-field dark energy
When taking the holographic principle into account, the vacuum energy will
acquire dynamical property that its equation of state is evolving. The current
available observational data imply that the holographic vacuum energy behaves
as quintom-type dark energy. We adopt the viewpoint of that the scalar field
models of dark energy are effective theories of an underlying theory of dark
energy. If we regard the scalar field model as an effective description of such
a holographic vacuum theory, we should be capable of using the scalar field
model to mimic the evolving behavior of the dynamical vacuum energy and
reconstructing this scalar field model according to the fits of the
observational dataset. We find the generalized ghost condensate model is a good
choice for depicting the holographic vacuum energy since it can easily realize
the quintom behavior. We thus reconstruct the function of the
generalized ghost condensate model using the best-fit results of the
observational data.Comment: 13 pages, 3 figures; references updated, accepted for publication in
Phys. Rev.
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