66 research outputs found
Exotic Gravitational Wave Signatures from Simultaneous Phase Transitions
We demonstrate that the relic gravitational wave background from a multi-step
phase transition may deviate from the simple sum of the single spectra, for
phase transitions with similar nucleation temperatures . We demonstrate
that the temperature range between the volume fractions
and occupied by the vacuum bubbles can span GeV. This
allows for a situation in which phase transitions overlap, such that the later
bubbles may nucleate both in high temperature and intermediate temperature
phases. Such scenarios may lead to more exotic gravitational wave spectra,
which cannot be fitted that of a consecutive PTs. We demonstrate this
explicitly in the singlet extension of the Standard Model. Finally, we comment
on potential additional effects due to the more exotic dynamics of overlapping
phase transitions.Comment: 25 pages, 7 figures. Published versio
Wess-Zumino Inflation in Light of Planck
We discuss cosmological inflation in the minimal Wess-Zumino model with a
single massive chiral supermultiplet. With suitable parameters and assuming a
plausible initial condition at the start of the inflationary epoch, the model
can yield scalar perturbations in the Cosmic Microwave Background (CMB) of the
correct strength with a spectral index n_s ~ 0.96 and a tensor-to-scalar
perturbation ratio r < 0.1, consistent with the Planck CMB data. We also
discuss the possibility of topological inflation within the Wess-Zumino model,
and the possibility of combining it with a seesaw model for neutrino masses.
This would violate R-parity, but at such a low rate that the lightest
supersymmetric particle would have a lifetime long enough to constitute the
astrophysical cold dark matter.Comment: 11 pages, 3 figure
Light Axion Emission and the Formation of Merging Binary Black Holes
We study the impact of stellar cooling due to light axion emission on the
formation and evolution of black hole binaries, via stable mass transfer and
the common envelope scenario. We find that in the presence of light axion
emission, no binary black hole mergers are formed with black holes in the lower
mass gap () via the common envelope formation
channel. In some systems, this happens because axions prevent Roche lobe
overflow. In others, they prevent the common envelope from being ejected. Our
results apply to axions with couplings (to photons) or (to electrons) and
masses . Light, weakly coupled particles may therefore
apparently produce a mass gap
in the LIGO/Virgo/KAGRA data, when no mass gap is present in the stellar
remnant population.Comment: 8 pages, 5 figures, reproduction package available here:
https://zenodo.org/record/694967
Dark Matter Annihilation and Pair-Instability Supernovae
We study the evolution of heavy stars () undergoing
pair-instability in the presence of annihilating dark matter. Focusing on the
scenario where the dark matter is in capture-annihilation equilibrium, we model
the profile of energy injections in the local thermal equilibrium
approximation. We find that significant changes to masses of astrophysical
black holes formed by (pulsational) pair-instability supernovae can occur when
the ambient dark matter density . There are two distinct outcomes, depending on the dark matter mass.
For masses GeV the DM is primarily confined to the core.
The annihilation increases the lifetime of core helium burning, resulting in
more oxygen being formed, fueling a more violent explosion during the
pair-instability-induced contraction. This drives stronger pulsations, leading
to lighter black holes being formed than predicted by the standard model. For
masses GeV there is significant dark matter in the
envelope, leading to a phase where the star is supported by the energy from the
annihilation. This reduces the core temperature and density, allowing the star
to evade the pair-instability allowing heavier black holes to be formed. We
find a mass gap for all models studied.Comment: Six Pages, Three Figure
Dark Matter (H)eats Young Planets
We study the effect of dark matter annihilation on the formation of Jovian
planets. We show that dark matter heat injections can slow or halt
Kelvin-Helmholtz contraction, preventing the accretion of hydrogen and helium
onto the solid core. The existence of Jupiter in our solar system can therefore
be used to infer constraints on dark matter with relatively strong interaction
cross sections. In the case of spin-dependent dark matter, we derive novel
constraints beyond the reach of current direct detection experiments. We
highlight the possibility of a positive detection using future observations by
JWST, which could reveal strongly varying planet morpholoiges close to our
Galactic Center.Comment: 8 pages, 4 figures, includes astronomical observations made with the
naked ey
Microlensing signatures of extended dark objects using machine learning
This paper presents a machine learning-based method for the detection of the
unique gravitational microlensing signatures of extended dark objects, such as
boson stars, axion miniclusters and subhalos. We adapt MicroLIA, a machine
learning-based package tailored to handle the challenges posed by low-cadence
data in microlensing surveys. Using realistic observational timestamps, our
models are trained on simulated light curves to distinguish between
microlensing by point-like and extended lenses, as well as from other object
classes which give a variable magnitude. We show that boson stars, examples of
objects with a relatively flat mass distribution, can be confidently identified
for . Intriguingly, we also find that more
sharply peaked structures, such as NFW-subhalos, can be distinctly recognized
from point-lenses under regular observation cadence. Our findings significantly
advance the potential of microlensing data in uncovering the elusive nature of
extended dark objects. The code and dataset used are also provided.Comment: 12 pages, 13 figures. Code provided in
https://gitlab.com/miguel.romao/microlensing-extended-objects-machine-learning
. Data provided in https://zenodo.org/records/1056686
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