9,519 research outputs found
The twisted fourth moment of the Riemann zeta function
We compute the asymptotics of the fourth moment of the Riemann zeta function
times an arbitrary Dirichlet polynomial of length Comment: 28 pages. v2: added reference
Langmuir Wave Generation Through A Neutrino Beam Instability
A standard version of a kinetic instability for the generation of Langmuir
waves by a beam of electrons is adapted to describe the analogous instability
due to a beam of neutrinos. The interaction between a Langmuir wave and a
neutrino is treated in the one-loop approximation to lowest order in an
expansion in in the standard electroweak model.
It is shown that this kinetic instability is far too weak to occur in a
suggested application to the reheating of the plasma behind a stalled shock in
a type II supernova (SN). This theory is also used to test the validity of a
previous analysis of a reactive neutrino beam instability and various
shortcomings of this theory are noted. In particular, it is noted that
relativistic plasma effects have a significant effect on the calculated growth
rates, and that any theoretical description of neutrino-plasma interactions
must be based directly on the electroweak theory. The basic scalings discussed
in this paper suggest that a more complete investigation of neutrino-plasma
processes should be undertaken to look for an efficient process capable of
driving the stalled shock of a type II SN.Comment: 23 pages, incl. 5 postscript figure
Coronagraph particulate measurements. Skylab flight experiment T025
Major results of the Skylab T025 Coronagraph experiment designed to monitor the particulate contamination about the spacecraft and to study the earth's atmospheric aerosol distribution are presented. A model for comet outbursts based on the properties of amorphous ice and ground based narrow-band and white light photography of comet Kohoutek ten days to perihelion are included. The effect of atmospheric refraction on the analysis of the T025 atmospheric data was also investigated
Half-life of the electron-capture decay of 97Ru: Precision measurement shows no temperature dependence
We have measured the half-life of the electron-capture (ec) decay of 97Ru in
a metallic environment, both at low temperature (19K), and also at room
temperature. We find the half-lives at both temperatures to be the same within
0.1%. This demonstrates that a recent claim that the ec decay half-life for 7Be
changes by $0.9% +/- 0.2% under similar circumstances certainly cannot be
generalized to other ec decays. Our results for the half-life of 97Ru,
2.8370(14)d at room temperature and 2.8382(14)d at 19K, are consistent with,
but much more precise than, previous room-temperature measurements. In
addition, we have also measured the half-lives of the beta-emitters 103Ru and
105Rh at both temperatures, and found them also to be unchanged.Comment: 6 pages, 6 figure
Unequal a priori Probability Multiple Hypothesis Testing in Space Domain Awareness with the Space Surveillance Telescope
This paper investigates the ability to improve Space Domain Awareness (SDA) by increasing the number of detectable Resident Space Objects (RSOs) from space surveillance sensors. With matched filter based techniques, the expected impulse response, or Point Spread Function (PSF), is compared against the received data. In the situation where the images are spatially undersampled, the modeled PSF may not match the received data if the RSO does not fall in the center of the pixel. This aliasing can be accounted for with a Multiple Hypothesis Test (MHT). Previously, proposed MHTs have implemented a test with an equal a priori prior probability assumption. This paper investigates using an unequal a priori probability MHT. To determine accurate a priori probabilities, three metrics are computed; they are correlation, physical distance, and empirical. Using the calculated a priori probabilities, a new algorithm is developed, and images from the Space Surveillance Telescope (SST) are analyzed. The number of detected objects by both an equal and unequal prior probabilities are compared while keeping the false alarm rate constant. Any additional number of detected objects will help improve SDA capabilities. Abstract © 2016 Optical Society of Americ
Pressure dependence of the magnetization of URu2Si2
The ground state of URu2Si2 changes from so-called hidden order (HO) to
large-moment antiferromagnetism (LMAF) upon applying hydrostatic pressure in
excess of 14 kbar. We report the dc-magnetization M(B,T,p) of URu2Si2 for
magnetic fields B up to 12 T, temperatures T in the range 2 to 100 K, and
pressure p up to 17 kbar. Remarkably, characteristic scales such as the
coherence temperature T*, the transition temperature T0, and the anisotropy in
the magnetization depend only weakly on the applied pressure. However, the
discontinuity in dM/dT at T0, which measures the magnetocaloric effect,
decreases nearly 50 % upon applying 17 kbar for M and B parallel to the
tetragonal c-axis, while it increases 15-fold for the a-axis. Our findings
suggest that the HO and LMAF phases have an astonishing degree of similarity in
their physical properties, but a key difference is the magnetocaloric effect
near T0 in the basal plane
Unusual Response to a Localized Perturbation in a Generalized Elastic Model
The generalized elastic model encompasses several physical systems such as
polymers, membranes, single file systems, fluctuating surfaces and rough
interfaces. We consider the case of an applied localized potential, namely an
external force acting only on a single (tagged) probe, leaving the rest of the
system unaffected. We derive the fractional Langevin equation for the tagged
probe, as well as for a generic (untagged) probe, where the force is not
directly applied. Within the framework of the fluctuation-dissipation
relations, we discuss the unexpected physical scenarios arising when the force
is constant and time periodic, whether or not the hydrodynamic interactions are
included in the model. For short times, in case of the constant force, we show
that the average drift is linear in time for long range hydrodynamic
interactions and behaves ballistically or exponentially for local hydrodynamic
interactions. Moreover, it can be opposite to the direction of external
disturbance for some values of the model's parameters. When the force is time
periodic, the effects are macroscopic: the system splits into two distinct
spatial regions whose size is proportional to the value of the applied
frequency. These two regions are characterized by different amplitudes and
phase shifts in the response dynamics
On the order of summability of the Fourier inversion formula
In this article we show that the order of the point value, in the sense of Łojasiewicz, of a tempered distribution and the order of summability of the pointwise Fourier inversion formula are closely related. Assuming that the order of the point values and certain order of growth at infinity are given for a tempered distribution, we estimate the order of summability of the Fourier inversion formula. For Fourier series, and in other cases, it is shown that if the distribution has a distributional point value of order k, then its Fourier series is e.v. Cesàro summable to the distributional point value of order k+1. Conversely, we also show that if the pointwise Fourier inversion formula is e.v. Cesàro summable of order k, then the distribution is the (k+1)-th derivative of a locally integrable function, and the distribution has a distributional point value of order k+2. We also establish connections between orders of summability and local behavior for other Fourier inversion problems
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