5,745 research outputs found
Are there Goldstone bosons in ?
We study the viability of spontaneous breaking of continuous symmetries in
theories with Lifshitz scaling, according to the number of space-time
dimensions and the dynamical scaling . Then, the answer to the question
in the title is no (quantum field theoretically) and yes (holographically).
With field theory tools, we show that symmetry breaking is indeed prevented by
large quantum fluctuations when , as expected from scaling
arguments. With holographic tools, on the other hand, we find nothing that
prevents the existence of a vacuum expectation value. This difference is made
possible by the large limit of holography. An important subtlety in this
last framework is that in order to get a proper description of a conserved
current, renormalization of the temporal mode of the bulk vector requires an
alternative quantization. We also comment on the implications of turning on
temperature.Comment: 18 pages. v2: a few clarifying comments added, matches published
versio
Asteroseismic inversions in the Kepler era: application to the Kepler Legacy sample
In the past few years, the CoRoT and Kepler missions have carried out what is
now called the space photometry revolution. This revolution is still ongoing
thanks to K2 and will be continued by the Tess and Plato2.0 missions. However,
the photometry revolution must also be followed by progress in stellar
modelling, in order to lead to more precise and accurate determinations of
fundamental stellar parameters such as masses, radii and ages. In this context,
the long-lasting problems related to mixing processes in stellar interior is
the main obstacle to further improvements of stellar modelling. In this
contribution, we will apply structural asteroseismic inversion techniques to
targets from the Kepler Legacy sample and analyse how these can help us
constrain the fundamental parameters and mixing processes in these stars. Our
approach is based on previous studies using the SOLA inversion technique to
determine integrated quantities such as the mean density, the acoustic radius,
and core conditions indicators, and has already been successfully applied to
the 16Cyg binary system. We will show how this technique can be applied to the
Kepler Legacy sample and how new indicators can help us to further constrain
the chemical composition profiles of stars as well as provide stringent
constraints on stellar ages.Comment: To appear in the proceedings of the Kasc 9 Tasc 2 worksho
Non-adiabatic pulsations in ESTER models
One of the greatest challenges in interpreting the pulsations of rapidly
rotating stars is mode identification, i.e. correctly matching theoretical
modes to observed pulsation frequencies. Indeed, the latest observations as
well as current theoretical results show the complexity of pulsation spectra in
such stars, and the lack of easily recognisable patterns. In the present
contribution, the latest results on non-adiabatic effects in such pulsations
are described, and we show how these come into play when identifying modes.
These calculations fully take into account the effects of rapid rotation,
including centrifugal distortion, and are based on models from the ESTER
project, currently the only rapidly rotating models in which the energy
conservation equation is satisfied, a prerequisite for calculating
non-adiabatic effects. Non-adiabatic effects determine which modes are excited
and play a key role in the near-surface pulsation-induced temperature
variations which intervene in multi-colour amplitude ratios and phase
differences, as well as line profile variations.Comment: Proceedings for the Joint TASC2 & KASC9 Workshop, Terceira, Azores,
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