8,359 research outputs found
Physical processes leading to surface inhomogeneities: the case of rotation
In this lecture I discuss the bulk surface heterogeneity of rotating stars,
namely gravity darkening. I especially detail the derivation of the omega-model
of Espinosa Lara & Rieutord (2011), which gives the gravity darkening in
early-type stars. I also discuss the problem of deriving gravity darkening in
stars owning a convective envelope and in those that are members of a binary
system.Comment: 23 pages, 11 figure, Lecture given to the school on the cartography
of the Sun and the stars (May 2014 in Besan\c{c}on), to appear in LNP, Neiner
and Rozelot edts V2: typos correcte
On the Naturalness of Higgs Inflation
We critically examine the recent claim that the Standard Model Higgs boson
could drive inflation in agreement with observations if has a strong coupling to the Ricci curvature scalar. We
first show that the effective theory approach upon which that claim is based
ceases to be valid beyond a cutoff scale , where is the
reduced Planck mass. We then argue that knowing the Higgs potential profile for
the field values relevant for inflation () requires knowledge of the ultraviolet completion of the SM beyond
. In absence of such microscopic theory, the extrapolation of the pure
SM potential beyond is unwarranted and the scenario is akin to other
ad-hoc inflaton potentials afflicted with significant fine-tuning. The
appealing naturalness of this minimal proposal is therefore lost.Comment: 9 pages. Replaced with published version, plus a footnote clarifying
the use of power counting estimate
Higgs Inflation as a Mirage
We discuss a simple unitarization of Higgs inflation that is genuinely weakly
coupled up to Planckian energies. A large non-minimal coupling between the
Higgs and the Ricci curvature is induced dynamically at intermediate energies,
as a simple ratio of mass scales. Despite not being dominated by the Higgs
field, inflationary dynamics simulates the `Higgs inflation' one would get by
blind extrapolation of the low-energy effective Lagrangian, at least
qualitatively. Hence, Higgs inflation arises as an approximate `mirage' picture
of the true dynamics. We further speculate on the generality of this phenomenon
and show that, if Higgs-inflation arises as an effective description, the
details of the UV completion are necessary to extract robust quantitative
predictions.Comment: 21 pages, 2 figure
Flux-cutting and flux-transport effects in type-II superconductor slabs in a parallel rotating magnetic field
The magnetic response of irreversible type-II superconductor slabs subjected
to in-plane rotating magnetic field is investigated by applying the circular,
elliptic, extended-elliptic, and rectangular flux-line-cutting critical-state
models. Specifically, the models have been applied to explain experiments on a
PbBi rotating disk in a fixed magnetic field , parallel to the flat
surfaces. Here, we have exploited the equivalency of the experimental situation
with that of a fixed disk under the action of a parallel magnetic field,
rotating in the opposite sense. The effect of both the magnitude of the
applied magnetic field and its angle of rotation upon the
magnetization of the superconductor sample is analyzed. When is smaller
than the penetration field , the magnetization components, parallel and
perpendicular to , oscillate with increasing the rotation angle. On
the other hand, if the magnitude of the applied field, , is larger than
, both magnetization components become constant functions of at
large rotation angles. The evolution of the magnetic induction profiles inside
the superconductor is also studied.Comment: 12 pages, 29 figure
A No-Lose Theorem for Higgs Searches at a Future Linear Collider
Assuming perturbativity up to a high energy scale GeV, we
demonstrate that a future linear collider operating at
500 GeV with 500 fb per year (such as the recently
proposed TESLA facility) will detect a Higgs boson signal regardless of the
complexity of the Higgs sector and of how the Higgs bosons decay.Comment: 4 pages, LaTe
Vacuum Decay Actions from Tunneling Potentials for General Spacetime Dimension
The tunneling potential method to calculate the action for vacuum decay is an
alternative to the Euclidean bounce method that has a number of attractive
features. In this paper we extend the formalism to general spacetime dimension
and use it to give simple proofs of several results. For Minkowski or
Anti de Sitter false vacua, we show that gravity or higher barriers increase
vacuum lifetime and describe a very clean picture of gravitational quenching of
vacuum decay. We also derive the thin-wall limit of the action, show how
detailed balance for dS to dS transitions works in the new formalism and how to
obtain potentials for which the vacuum decay solution can be obtained
analytically.Comment: 17 pages plus appendice
Moving embedded lattice solitons
It was recently proved that isolated unstable "embedded lattice solitons"
(ELS) may exist in discrete systems. The discovery of these ELS gives rise to
relevant questions such as the following: are there continuous families of
ELS?, can ELS be stable?, is it possible for ELS to move along the lattice?,
how do ELS interact?. The present work addresses these questions by showing
that a novel differential-difference equation (a discrete version of a complex
mKdV equation) has a two-parameter continuous family of exact ELS. The
numerical tests reveal that these solitons are stable and robust enough to
withstand collisions. The model may apply to the description of a Bose-Einstein
condensate with dipole-dipole interactions between the atoms, trapped in a deep
optical-lattice potential.Comment: 13 pages, 11 figure
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