13,137 research outputs found
The Pattern Speeds of NGC 3031, NGC 2366, and DDO 154 as Functions of Radius
The pattern speeds of NGC 3031, NGC 2366, and DDO 154 are measured using a
solution of the Tremaine-Weinberg equations derived in a previous paper. Four
different data sets of NGC 3031 produce consistent results despite differences
in angular resolution, spectral resolution, and sensitivities to structures on
different scales. The results for NGC 3031 show that the pattern speed is more
similar to the material speed than it is to the speed of a rigidly rotating
pattern, and that there are no clear indications of unique corotation or
Lindblad resonances. Unlike NGC 3031, the results for NGC 2366 and DDO 154 show
clear departures from the material speed. The results for NGC 2366 and DDO 154
also show that the solution method can produce meaningful results that are
simple to interpret even if there is not a coherent or well-defined pattern in
the data. The angular resolution of a data set has the greatest affect on the
results, especially for determining the radial behavior of the pattern speed,
and whether there is a single, global pattern speed.Comment: Accepted for publication in The Astrophysical Journa
Exotic circuit elements from zero-modes in hybrid superconductor/quantum Hall systems
Heterostructures formed by quantum Hall systems and superconductors have
recently been shown to support widely coveted Majorana fermion zero-modes and
still more exotic `parafermionic' generalizations. Here we establish that
probing such zero-modes using quantum Hall edge states yields non-local
transport signatures that pave the way towards a variety of novel circuit
elements. In particular, we demonstrate quite generally that at low energies
the zero-modes convert chirally moving quasiparticles into oppositely charged
quasiholes propagating in the same direction---that is, they swap the sign of
the chiral edge currents. One may then construct new and potentially useful
circuit elements using this `perfect Andreev conversion' process, including
superconducting current and voltage mirrors as well as transistors for
fractional charge currents. Characterization of these circuit elements should
provide striking evidence of the zero-mode physics.Comment: 7 pages, 5 figures, v2: references adde
Exotic non-Abelian anyons from conventional fractional quantum Hall states
Non-Abelian anyons--particles whose exchange noncommutatively transforms a
system's quantum state--are widely sought for the exotic fundamental physics
they harbor as well as for quantum computing applications. There now exist
numerous blueprints for stabilizing the simplest type of non-Abelian anyon,
defects binding Majorana modes, by judiciously interfacing widely available
materials. Following this line of attack, we introduce a device fabricated from
conventional fractional quantum Hall states and s-wave superconductors that
supports exotic non-Abelian anyons that bind `parafermions', which can be
viewed as fractionalized Majorana fermions. We show that these modes can be
experimentally identified (and distinguished from Majoranas) using Josephson
measurements. We also provide a practical recipe for braiding parafermions and
show that they give rise to non-Abelian statistics. Interestingly, braiding in
our setup produces a richer set of topologically protected qubit operations
when compared to the Majorana case. As a byproduct, we establish a new,
experimentally realistic Majorana platform in weakly spin-orbit-coupled
materials such as GaAs.Comment: 12 pages, 4 figure
Supermassive Black Holes from Ultra-Strongly Self-Interacting Dark Matter
We consider the cosmological consequences if a small fraction () of the dark matter is ultra-strongly self-interacting, with an elastic
self-interaction cross-section per unit mass .
This possibility evades all current constraints that assume that the
self-interacting component makes up the majority of the dark matter.
Nevertheless, even a small fraction of ultra-strongly self-interacting dark
matter (uSIDM) can have observable consequences on astrophysical scales. In
particular, the uSIDM subcomponent can undergo gravothermal collapse and form
seed black holes in the center of a halo. These seed black holes, which form
within several hundred halo interaction times, contain a few percent of the
total uSIDM mass in the halo. For reasonable values of , these black
holes can form at high enough redshifts to grow to quasars
by , alleviating tension within the standard CDM
cosmology. The ubiquitous formation of central black holes in halos could also
create cores in dwarf galaxies by ejecting matter during binary black hole
mergers, potentially resolving the "too big to fail" problem.Comment: submitted to Ap
Anatomy of beyond the Standard Model
We present for the first time a model-independent anatomy of the ratio
in the context of the effective
theory with operators invariant under QCD and QED and in the context of the
Standard Model Effective Field Theory (SMEFT) with the operators invariant
under the full SM gauge group. Our goal is to identify the new physics
scenarios that are probed by this ratio and which could help to explain a
possible deviation from the SM that is hinted by the data. To this end we
derive a master formula for , which can be applied to
any theory beyond the Standard Model (BSM) in which the Wilson coefficients of
all contributing operators have been calculated at the electroweak scale. The
relevant hadronic matrix elements of BSM operators are from the Dual QCD
approach and the SM ones from lattice QCD. Within SMEFT, the constraints from
and mixing as well as electric dipole moments limit significantly
potential new physics contributions to . Correlations
of with decays are briefly
discussed. Building on our EFT analysis and the model-independent constraints,
we discuss implications of a possible deviation from the SM in
for model building, highlighting the role of the new
scalar and tensor matrix elements in models with scalar mediators.Comment: 47 pages, 4 figures. v3: signs in tables 6-10 corrected, numerical
results and conclusions unchange
Spatially Resolved Stellar Populations of Eight GOODS-South Active Galactic Nuclei at z ~ 1
We present a pilot study of the stellar populations of eight active galactic nucleus (AGN) hosts at z ~ 1 and compare with (1) lower redshift samples and (2) a sample of nonactive galaxies of similar redshift. We utilize K' images in the Great Observatories Origins Deep Survey South field obtained with the laser guide star adaptive optics system at Keck Observatory. We combine these K' data with B, V, i, and z imaging from the Advanced Camera for Surveys on Hubble Space Telescope to give multicolor photometry at a matched spatial resolution better than 100 mas in all bands. The hosts harbor AGNs as inferred from their high X-ray luminosities (LX > 10^42 erg s^–1) or mid-IR colors. We find a correlation between the presence of younger stellar populations and the strength of the AGN, as measured with [O III] line luminosity or X-ray (2-10 keV) luminosity. This finding is consistent with similar studies at lower redshift. Of the three Type II galaxies, two are disk galaxies and one is of irregular type, while in the Type I sample there are only one disk-like source and four sources with smooth, elliptical/spheroidal morphologies. In addition, the mid-IR spectral energy distributions of the strong Type II AGNs indicate that they are excited to Luminous InfraRed Galaxy (LIRG) status via galactic starbursting, while the strong Type I AGNs are excited to LIRG status via hot dust surrounding the central AGN. This supports the notion that the obscured nature of Type II AGNs at z ~ 1 is connected with global starbursting and that they may be extincted by kpc-scale dusty features that are by-products of this starbursting
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