5,253 research outputs found
Multiplicity one for -functions and applications
We give conditions for when two Euler products are the same given that they
satisfy a functional equation and their coefficients satisfy a partial
Ramanujan bound and do not differ by too much. Additionally, we prove a number
of multiplicity one type results for the number-theoretic objects attached to
-functions. These results follow from our main result about -functions
Characterizations of the Saito-Kurokawa lifting: a survey
There are a variety of characterizations of Saito-Kurokawa lifts from
elliptic modular forms to Siegel modular forms of degree 2. In addition to
giving a survey of known characterizations, we apply a recent result of
Weissauer to provide a number of new and simpler characterizations of
Saito-Kurokawa lifts
Deep Equatorial Pacific Ocean Oxygenation and Atmospheric CO\u3csub\u3e2\u3c/sub\u3e Over the Last Ice Age
Ventilation of carbon stored in the deep ocean is thought to play an important role in atmospheric CO2 increases associated with Pleistocene deglaciations. The presence of this respired carbon has been recorded by an array of paleoceanographic proxies from various locations across the global ocean. Here we present a new sediment core from the Eastern Equatorial Pacific (EEP) Ocean spanning the last 180,000 years and reconstruct high-resolution 230Th-derived fluxes of 232Th and excess barium, along with redox-sensitive uranium concentrations to examine past variations in dust delivery, export productivity, and bottom-water oxygenation, respectively. Our bottom-water oxygenation record is compared to other similar high-resolution records from across the Pacific and in the Southern Ocean. We suggest that the deep Pacific is a site of respired carbon storage associated with periods of decreased global atmospheric CO2 concentration during the LGM, confirming the conclusions from a wealth of previous studies. However, our study is the first to show a similar relationship beyond the last glacial, extending to at least 70,000 years
Geometrical locus of massive test particle orbits in the space of physical parameters in Kerr space-time
Gravitational radiation of binary systems can be studied by using the
adiabatic approximation in General Relativity. In this approach a small
astrophysical object follows a trajectory consisting of a chained series of
bounded geodesics (orbits) in the outer region of a Kerr Black Hole,
representing the space time created by a bigger object. In our paper we study
the entire class of orbits, both of constant radius (spherical orbits), as well
as non-null eccentricity orbits, showing a number of properties on the physical
parameters and trajectories. The main result is the determination of the
geometrical locus of all the orbits in the space of physical parameters in Kerr
space-time. This becomes a powerful tool to know if different orbits can be
connected by a continuous change of their physical parameters. A discussion on
the influence of different values of the angular momentum of the hole is given.
Main results have been obtained by analytical methods.Comment: 26 pages, 12 figure
Mapping spacetimes with LISA: inspiral of a test-body in a `quasi-Kerr' field
The future LISA detector will constitute the prime instrument for
high-precision gravitational wave observations.LISA is expected to provide
information for the properties of spacetime in the vicinity of massive black
holes which reside in galactic nuclei.Such black holes can capture stellar-mass
compact objects, which afterwards slowly inspiral,radiating gravitational
waves.The body's orbital motion and the associated waveform carry information
about the spacetime metric of the massive black hole,and it is possible to
extract this information and experimentally identify (or not!) a Kerr black
hole.In this paper we lay the foundations for a practical `spacetime-mapping'
framework. Our work is based on the assumption that the massive body is not
necessarily a Kerr black hole, and that the vacuum exterior spacetime is
stationary axisymmetric,described by a metric which deviates slightly from the
Kerr metric. We first provide a simple recipe for building such a `quasi-Kerr'
metric by adding to the Kerr metric the deviation in the value of the
quadrupole moment. We then study geodesic motion in this metric,focusing on
equatorial orbits. We proceed by computing `kludge' waveforms which we compare
with their Kerr counterparts. We find that a modest deviation from the Kerr
metric is sufficient for producing a significant mismatch between the
waveforms, provided we fix the orbital parameters. This result suggests that an
attempt to use Kerr waveform templates for studying EMRIs around a non-Kerr
object might result in serious loss of signal-to-noise ratio and total number
of detected events. The waveform comparisons also unveil a `confusion' problem,
that is the possibility of matching a true non-Kerr waveform with a Kerr
template of different orbital parameters.Comment: 19 pages, 6 figure
Effect of hydrocarbon adsorption on the wettability of rare earth oxide ceramics
Vapor condensation is routinely used as an effective means of transferring heat, with dropwise condensation exhibiting a 5 − 7x heat transfer improvement compared to filmwise condensation. However, state-of-the-art techniques to promote dropwise condensation rely on functional hydrophobic coatings, which are often not robust and therefore undesirable for industrial implementation. Natural surface contamination due to hydrocarbon adsorption, particularly on noble metals, has been explored as an alternative approach to realize stable dropwise condensing surfaces. While noble metals are prohibitively expensive, the recent discovery of robust rare earth oxide (REO) hydrophobicity has generated interest for dropwise condensation applications due to material costs approaching 1% of gold; however, the underlying mechanism of REO hydrophobicity remains under debate. In this work, we show through careful experiments and modeling that REO hydrophobicity occurs due to the same hydrocarbon adsorption mechanism seen previously on noble metals. To investigate adsorption dynamics, we studied holmia and ceria REOs, along with control samples of gold and silica, via X-Ray photoelectron spectroscopy (XPS) and dynamic time-resolved contact angle measurements. The contact angle and surface carbon percent started at ≈0 on in-situ argon-plasma-cleaned samples and increased asymptotically over time after exposure to laboratory air, with the rare earth oxides displaying hydrophobic (>90°) advancing contact angle behavior at long times (>4 days). The results indicate that REOs are in fact hydrophilic when clean and become hydrophobic due to hydrocarbon adsorption. Furthermore, this study provides insight into how REOs can be used to promote stable dropwise condensation, which is important for the development of enhanced phase change surfaces.United States. Office of Naval ResearchUnited States. Dept. of Energy (MIT S3TEC Energy Research Frontier Center, Award No. DE- FG02-09ER46577)National Science Foundation (U.S.) (Graduate research fellowship)National Science Foundation (U.S.) (Graduate Research Fellowship Program, Grant No. 1122374)Irish Research Council for Science, Engineering, and Technology (Marie Curie Actions under FP7
TID Tolerance of Popular CubeSat Components
In this paper we report total dose test results of COTS components commonly used on CubeSats. We investigate a variety of analog integrated circuits, a popular microcontroller (PIC24) as well as SD memory card
An Asymmetric Double-Degenerate Type Ia Supernova Explosion with a Surviving Companion Star
We present nebular spectroscopy of SN 2020hvf, a Type Ia supernova (SN Ia)
with an early bump in its light curve. SN 2020hvf shares many spectroscopic and
photometric similarities to the carbon-rich high-luminosity "03fg-like" SNe Ia.
At 240 days after peak brightness, we detect unambiguous emission from [Ca
II] 7291, 7324 which is never observed in normal-SNe Ia and
only seen in peculiar subclasses. SN 2020hvf displays "saw-tooth" emission
profiles near 7300 A that cannot be explained with single symmetric velocity
components of [Fe II], [Ni II], and [Ca II], indicating an asymmetric
explosion. The broad [Ca II] emission is best modeled by two velocity
components offset by 1,220 km s, which could be caused by ejecta
associated with each star in the progenitor system, separated by their orbital
velocity. For the first time in a SN Ia, we identify narrow ( km s) [Ca II] emission, which we associate with a wind from a
surviving, puffed-up companion star. Few published spectra have sufficient
resolution and signal-to-noise ratio necessary to detect similar narrow [Ca II]
emission, however, we have detected similar line profiles in other 03fg-like
SNe Ia. The extremely narrow velocity width of [Ca II] has only otherwise been
observed in SNe Iax at late times. Since this event likely had a
double-degenerate "super-Chandrasekhar" mass progenitor system, we suggest that
a single white dwarf (WD) was fully disrupted and a wind from a surviving
companion WD is producing the observed narrow emission. It is unclear if this
unique progenitor and explosion scenario can explain the diversity of 03fg-like
SNe Ia, potentially indicating that multiple progenitor channels contribute to
this subclass.Comment: 18 pages, 10 figures, Published in Ap
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