290 research outputs found
Osmotic pressure of matter and vacuum energy
The walls of the box which contains matter represent a membrane that allows
the relativistic quantum vacuum to pass but not matter. That is why the
pressure of matter in the box may be considered as the analog of the osmotic
pressure. However, we demonstrate that the osmotic pressure of matter is
modified due to interaction of matter with vacuum. This interaction induces the
nonzero negative vacuum pressure inside the box, as a result the measured
osmotic pressure becomes smaller than the matter pressure. As distinct from the
Casimir effect, this induced vacuum pressure is the bulk effect and does not
depend on the size of the box. This effect dominates in the thermodynamic limit
of the infinite volume of the box. Analog of this effect has been observed in
the dilute solution of 3He in liquid 4He, where the superfluid 4He plays the
role of the non-relativistic quantum vacuum, and 3He atoms play the role of
matter.Comment: 5 pages, 1 figure, JETP Lett. style, version accepted in JETP Letter
Energy barrier in the two-Higgs model
The electroweak model is extended by a second Higgs doublet and a numerical
investigation of static, finite energy classical solutions is performed. The
results indicate that for a large domain of the parameters of the Higgs
potential, the energy barrier between topologically distinct vacua of the
Lagrangian is constituted by a bisphaleron.Comment: 19 pages, including 4 eps figures, LaTex format, new results include
Note on a new fundamental length scale instead of the Newtonian constant
The newly proposed entropic gravity suggests gravity as an emergent force
rather than a fundamental one. In this approach, the Newtonian constant
does not play a fundamental role any more, and a new fundamental constant is
required to replace its position. This request also arises from some
philosophical considerations to contemplate the physical foundations for the
unification of theories. We here consider the suggestion to derive from
more fundamental quantities in the presence of a new fundamental length scale
, which is suspected to originate from the structure of quantum space-time,
and can be measured directly from Lorentz-violating observations. Our results
are relevant to the fundamental understanding of physics, and more practically,
of natural units, as well as explanations of experimental constraints in
searching for Lorentz violation.Comment: 10 latex pages, final version for journal publicatio
On Axially Symmetric Solutions in the Electroweak Theory
We present the general ansatz, the energy density and the Chern-Simons charge
for static axially symmetric configurations in the bosonic sector of the
electroweak theory. Containing the sphaleron, the multisphalerons and the
sphaleron-antisphaleron pair at finite mixing angle, the ansatz further allows
the construction of the sphaleron and multisphaleron barriers and of the
bisphalerons at finite mixing angle. We conjecture that further solutions
exist.Comment: 17 pages, latex, THU-94/0
Newtonian gravity as an entropic force: Towards a derivation of G
It has been suggested that the Newtonian gravitational force may emerge as an
entropic force from a holographic microscopic theory. In this framework, the
possibility is reconsidered that Newton's gravitational coupling constant G can
be derived from the fundamental constants of the underlying microscopic theory.Comment: 10 pages. v6: published versio
Towards a solution of the cosmological constant problem
The standard model of elementary particle physics and the theory of general
relativity can be extended by the introduction of a vacuum variable which is
responsible for the near vanishing of the present cosmological constant (vacuum
energy density). The explicit realization of this vacuum variable can be via a
three-form gauge field, an aether-type velocity field, or any other field
appropriate for the description of the equilibrium state corresponding to the
Lorentz-invariant quantum vacuum. The extended theory has, without fine-tuning,
a Minkowski-type solution of the field equations with spacetime-independent
fields and provides, therefore, a possible solution of the main cosmological
constant problem.Comment: 7 pages; v6: published versio
Sensitivity of Hawking radiation to superluminal dispersion relations
We analyze the Hawking radiation process due to collapsing configurations in
the presence of superluminal modifications of the dispersion relation. With
such superluminal dispersion relations, the horizon effectively becomes a
frequency-dependent concept. In particular, at every moment of the collapse,
there is a critical frequency above which no horizon is experienced. We show
that, as a consequence, the late-time radiation suffers strong modifications,
both quantitative and qualitative, compared to the standard Hawking picture.
Concretely, we show that the radiation spectrum becomes dependent on the
measuring time, on the surface gravities associated with different frequencies,
and on the critical frequency. Even if the critical frequency is well above the
Planck scale, important modifications still show up.Comment: 14 pages, 7 figures. Extensive paragraph added in conclusions to
clarify obtained result
Three fully polarized fermions close to a p-wave Feshbach resonance
We study the three-body problem for three atomic fermions, in the same spin
state, experiencing a resonant interaction in the p-wave channel via a Feshbach
resonance represented by a two-channel model. The rate of inelastic processes
due to recombination to deeply bound dimers is then estimated from the
three-body solution using a simple prescription. We obtain numerical and
analytical predictions for most of the experimentally relevant quantities that
can be extracted from the three-body solution: the existence of weakly bound
trimers and their lifetime, the low-energy elastic and inelastic scattering
properties of an atom on a weakly bound dimer (including the atom-dimer
scattering length and scattering volume), and the recombination rates for three
colliding atoms towards weakly bound and deeply bound dimers. The effect of
"background" non-resonant interactions in the open channel of the two-channel
model is also calculated and allows to determine which three-body quantities
are `universal' and which on the contrary depend on the details of the model.Comment: 31 pages, 12 figure
Spontaneous Breaking of Lorentz Invariance
We describe how a stable effective theory in which particles of the same
fermion number attract may spontaneously break Lorentz invariance by giving
non-zero fermion number density to the vacuum (and therefore dynamically
generating a chemical potential term). This mecanism yields a finite vacuum
expectation value could relate to work on signals of Lorentz violation
in electrodynamics.Comment: revtex4, 11 pages, 5 figures; v2:references added; v3:more references
added, typos fixed, some points in sect. IV clarified; v4:even more
references added, discussion in sect. V extended; v5:replaced to match
published version (minor corrections of form
Transgressive segregation of primary and secondary metabolites in F2 hybrids between Jacobaea aquatica and J. vulgaris
Hybridization between plant species can have a number of biological consequences; interspecific hybridization has been tied to speciation events, biological invasions, and diversification at the level of genes, metabolites, and phenotypes. This study aims to provide evidence of transgressive segregation in the expression of primary and secondary metabolites in hybrids between Jacobaeavulgaris and J. aquaticus using an NMR-based metabolomic profiling approach. A number of F2 hybrid genotypes exhibited metabolomic profiles that were outside the range encompassed by parental species. Expression of a number of primary and secondary metabolites, including jacaronone analogues, chlorogenic acid, sucrose, glucose, malic acid, and two amino acids was extreme in some F2 hybrid genotypes compared to parental genotypes, and citric acid was expressed in highest concentrations in J. vulgaris. Metabolomic profiling based on NMR is a useful tool for quantifying genetically controlled differences between major primary and secondary metabolites among plant genotypes. Interspecific plant hybrids in general, and specifically hybrids between J. vulgaris and J. aquatica, will be useful for disentangling the ecological role of suites of primary and secondary metabolites in plants, because interspecific hybridization generates extreme metabolomic diversity compared to that normally observed between parental genotypes
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