14 research outputs found
Higher Spin Dark Matter
Little is known about dark matter beyond the fact that it does not interact
with the standard model or itself, or else does so incredibly weakly. A natural
candidate, given the history of no-go theorems against their interactions, are
higher spin fields. Here we develop the scenario of higher spin (spin )
dark matter. We show that the gravitational production of superheavy bosonic
higher spin fields during inflation can provide all the dark matter we observe
today. We consider the observable signatures, and find a potential
characteristic signature of bosonic higher spin dark matter in directional
direct detection; we find that there are distinct spin-dependent contributions
to the double differential recoil rate, which complement the oscillatory
imprint of higher spin fields in the cosmic microwave background. We consider
the extension to higher spin fermions and supersymmetric higher spins.Comment: 11 pages, 2 figure
Cosmological Implications of Kalb-Ramond-Like-Particles
The Kalb-Ramond field is an antisymmetric, rank-two tensor field which most
notably appears in the context of string theory, but has largely been
unexplored in the context of cosmology. In this work, motivated by the
Kalb-Ramond field in string theory, and antisymmetric tensor fields that emerge
in effective field theories ranging from particle physics to condensed matter,
we study the primordial production of interacting massive
Kalb-Ramond-like-particles (KRLPs). KRLPs contain features of both dark photon
and axion models, which can be appreciated via their duality properties. While
the massless non-interacting KRLP is dual to a pseudoscalar, and the massive
non-interacting KRLP is dual to a pseudovector, the interacting massive KRLP
can be distinguished from its scalar and vector counterparts. We study
early-universe production of KRLPs via the freeze-in mechanism, considering a
`dark photon-like' interaction, an `axion-like' interaction, and a `Higgs
portal' interaction, as well as production via cosmological gravitational
particle production. We find that as a dark matter candidate, KRLPs can be
produced by all of the above mechanisms and account for the relic density of
dark matter today for a wide range of masses. Finally, we comment on the
potential to obtain both warm and cold dark matter subcomponents, and speculate
on observational and experimental prospects.Comment: 40 pages, 3 figure
Thick disks in the Hubble Space Telescope Frontier Fields
Thick disk evolution is studied using edge-on galaxies in two Hubble Space
Telescope Frontier Field Parallels. The galaxies were separated into 72 clumpy
types and 35 spiral types with bulges. Perpendicular light profiles in F435W,
F606W and F814W (B, V and I) passbands were measured at 1 pixel intervals along
the major axes and fitted to sech^2 functions convolved with the instrument
line spread function (LSF). The LSF was determined from the average point
spread function (PSF) of ~20 stars in each passband and field, convolved with a
line of uniform brightness to simulate disk blurring. A spread function for a
clumpy disk was also used for comparison. The resulting scale heights were
found to be proportional to galactic mass, with the average height for a
10^9.5-10^10.5 Msun galaxy at z=1.5-2.5 equal to 0.63+-0.24 kpc. This value is
probably the result of a blend between thin and thick disk components that
cannot be resolved. Evidence for such two-component structure is present in an
inverse correlation between height and midplane surface brightness. Models
suggest that the thick disk is observed best between the clumps, and there the
average scale height is 1.06+-0.43 kpc for the same mass and redshift. A
0.63+-0.68 mag V-I color differential with height is also evidence for a
mixture of thin and thick components.Comment: 11 pages, 19 figures, accepted by Ap
Towards A Direct Detection of the Spin of Dark Matter
We investigate the contribution of higher spin particles in the signal of
direct detection experiments searching for dark matter. We consider a bosonic
or fermionic higher spin dark matter (HSDM) candidate which interacts with the
Standard Model via a dark U(1) mediator. For a particular subclass of
interactions, spin-polarized targets may be used for spin determination: The
angular dependence of scatterings can distinguish integer (spin-) vs.
half-integer (spin-), while the recoil energy dependence of the signal
determines . We consider also the signal of a supersymmetric higher spin
dark sector, which suggests a characteristic signal (''SUSY Rilles'') for
directional direct detection.Comment: Matches published version in PL
The June 2016 Optical and Gamma-Ray Outburst and Optical Micro-Variability of the Blazar 3C454.3
The quasar 3C454.3 underwent a uniquely-structured multi-frequency outburst
in June 2016. The blazar was observed in the optical band by several
ground-based telescopes in photometric and polarimetric modes, at -ray
frequencies by the \emph{Fermi}\ Large Area Telescope, and at 43 GHz with the
Very Long Baseline Array. The maximum flux density was observed on 2016 June 24
at both optical and -ray frequencies, reaching
mJy and ph cm s, respectively. The June 2016
outburst possessed a precipitous decay at both -ray and optical
frequencies, with the source decreasing in flux density by a factor of 4 over a
24-hour period in band. Intraday variability was observed throughout the
outburst, with flux density changes between 1 and 5 mJy over the course of a
night. The precipitous decay featured statistically significant quasi-periodic
micro-variability oscillations with an amplitude of - about the
mean trend and a characteristic period of 36 minutes. The optical degree of
polarization jumped from to nearly 20\% during the outburst, while
the position angle varied by \sim120\degr. A knot was ejected from the 43 GHz
core on 2016 Feb 25, moving at an apparent speed .
From the observed minimum timescale of variability
hr and derived Doppler factor
, we find a size of the emission region
cm. If the quasi-periodic micro-variability
oscillations are caused by periodic variations of the Doppler factor of
emission from a turbulent vortex, we derive a rotational speed of the vortex
.Comment: 19 pages, 13 figures, 3 tables, accepted to the Astrophysical Journal
2019 March
Black Hole Superradiance in Dynamical Chern-Simons Gravity
Black hole superradiance provides a window into the dynamics of light scalar
fields and their interactions close to a rotating black hole. Due to the
rotation of the black hole, the amplitude of the scalar field becomes
magnified, leading to a "black hole bomb" effect. Recent work has demonstrated
that rotating black holes in dynamical Chern-Simons gravity possess unique
structures, the "Chern-Simons caps," which may influence the behavior of matter
near the black hole. Motivated by the presence of these caps, we study
superradiance in dynamical Chern-Simons gravity in the context of a slowly
rotating black hole. We find that additional modes are excited and contribute
to the superradiance beyond what is expected for a Kerr black hole. Studying
the superradiant spectrum of perturbations, we find that the Chern-Simons
contributions give rise to small corrections to the angular dependence of the
resulting scalar cloud. Finally, we comment on potential observable
consequences and future avenues for investigation.Comment: Error in Eq. 51-53 and 69-71 corrected, updated discussio
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Towards a direct detection of the spin of dark matter
We investigate the contribution of higher spin particles in the signal of direct detection searches for dark matter. We consider a bosonic or fermionic higher spin dark matter (HSDM) candidate which interacts with the Standard Model via a dark U(1) mediator. For a particular subclass of interactions, spin-polarized targets may be used for spin determination: The angular dependence of scatterings can distinguish integer (spin-s) vs. half-integer (spin-s + 1 / 2), while the recoil energy dependence of the signal determines s. We consider also the signal of a supersymmetric higher spin dark sector, which suggests a characteristic signal (“SUSY Rilles”) for directional direct detection
Gamma-ray Transient Network Science Analysis Group Report
International audienceThe Interplanetary Network (IPN) is a detection, localization and alert system that utilizes the arrival time of transient signals in gamma-ray detectors on spacecraft separated by planetary baselines to geometrically locate the origin of these transients. Due to the changing astrophysical landscape and the new emphasis on time domain and multi-messenger astrophysics (TDAMM) from the Pathways to Discovery in Astronomy and Astrophysics for the 2020s, this Gamma-ray Transient Network Science Analysis Group was tasked to understand the role of the IPN and high-energy monitors in this new era. The charge includes describing the science made possible with these facilities, tracing the corresponding requirements and capabilities, and highlighting where improved operations of existing instruments and the IPN would enhance TDAMM science. While this study considers the full multiwavelength and multimessenger context, the findings are specific to space-based high-energy monitors. These facilities are important both for full characterization of these transients as well as facilitating follow-up observations through discovery and localization. The full document reports a brief history of this field, followed by our detailed analyses and findings in some 68 pages, providing a holistic overview of the role of the IPN and high-energy monitors in the coming decades