261 research outputs found
User's manual for Axisymmetric Diffuser Duct (ADD) code. Volume 1: General ADD code description
This User's Manual contains a complete description of the computer codes known as the AXISYMMETRIC DIFFUSER DUCT code or ADD code. It includes a list of references which describe the formulation of the ADD code and comparisons of calculation with experimental flows. The input/output and general use of the code is described in the first volume. The second volume contains a detailed description of the code including the global structure of the code, list of FORTRAN variables, and descriptions of the subroutines. The third volume contains a detailed description of the CODUCT code which generates coordinate systems for arbitrary axisymmetric ducts
User's manual for Axisymmetric Diffuser Duct (ADD) code. Volume 3: ADD code coordinate generator
This User's Manual contains a complete description of the computer codes known as the Axisymmetric Diffuser Duct (ADD) code. It includes a list of references which describe the formulation of the ADD code and comparisons of calculation with experimental flows. The input/output and general use of the code is described in the first volume. The second volume contains a detailed description of the code including the global structure of the code, list of FORTRAN variables, and descriptions of the subroutines. The third volume contains a detailed description of the CODUCT code which generates coordinate systems for arbitrary axisymmetric ducts
Improved flux limits for neutrinos with energies above 10 eV from observations with the Westerbork Synthesis Radio Telescope
Particle cascades initiated by ultra-high energy (UHE) neutrinos in the lunar
regolith will emit an electromagnetic pulse with a time duration of the order
of nano seconds through a process known as the Askaryan effect. It has been
shown that in an observing window around 150 MHz there is a maximum chance for
detecting this radiation with radio telescopes commonly used in astronomy. In
50 hours of observation time with the Westerbork Synthesis Radio Telescope
array we have set a new limit on the flux of neutrinos, summed over all
flavors, with energies in excess of eV.Comment: Submitted to Phys. Rev. Let
Prospects for Lunar Satellite Detection of Radio Pulses from Ultrahigh Energy Neutrinos Interacting with the Moon
The Moon provides a huge effective detector volume for ultrahigh energy
cosmic neutrinos, which generate coherent radio pulses in the lunar surface
layer due to the Askaryan effect. In light of presently considered lunar
missions, we propose radio measurements from a Moon-orbiting satellite. First
systematic Monte Carlo simulations demonstrate the detectability of Askaryan
pulses from neutrinos with energies above 10^{20} eV, i.e. near and above the
interesting GZK limit, at the very low fluxes predicted in different scenarios.Comment: RevTeX (4 pages, 2 figures). v2 includes updated results and extended
discussio
Determining neutrino absorption spectra at Ultra-High Energies
A very efficient method to measure the flux of Ultra-high energy (UHE)
neutrinos is through the detection of radio waves which are emitted by the
particle shower in the lunar regolith. The highest acceptance is reached for
radio waves in the frequency band of 100-200 MHz which can be measured with
modern radio telescopes. In this work we investigate the sensitivity of this
detection method to structures in the UHE neutrino spectrum caused by their
absorption on the low-energy relic anti-neutrino background through the Z-boson
resonance. The position of the absorption peak is sensitive to the neutrino
mass and the redshift of the source. A new generation of low-frequency digital
radio telescopes will provide excellent detection capabilities for measuring
these radio pulses, thus making our consideration here very timely.Comment: 7 figures, submitted to JCAP revision: References updated and minor
changes in tex
On defining the Hamiltonian beyond quantum theory
Energy is a crucial concept within classical and quantum physics. An
essential tool to quantify energy is the Hamiltonian. Here, we consider how to
define a Hamiltonian in general probabilistic theories, a framework in which
quantum theory is a special case. We list desiderata which the definition
should meet. For 3-dimensional systems, we provide a fully-defined recipe which
satisfies these desiderata. We discuss the higher dimensional case where some
freedom of choice is left remaining. We apply the definition to example toy
theories, and discuss how the quantum notion of time evolution as a phase
between energy eigenstates generalises to other theories.Comment: Authors' accepted manuscript for inclusion in the Foundations of
Physics topical collection on Foundational Aspects of Quantum Informatio
The Parallax, Mass and Age of the PSR J2145-0750 binary system
We present results of timing measurements of the binary millisecond pulsar
PSR J2145-0750. Combining timing data obtained with the Effelsberg and Lovell
radio telescopes we measure a significant timing parallax of 2.0(6) mas placing
the system at 500 pc distance to the solar system. The detected secular change
of the projected semi-major axis of the orbit
lt-s s, where , is caused by the proper motion of
the system. With this measurement we can constrain the orbital inclination
angle to i<61\degr, with a median likelihood value of 46\degr which is
consistent with results from polarimetric studies of the pulsar magnetosphere.
This constraint together with the non-detection of Shapiro delay rules out
certain combinations of the companion mass, , and the inclination, .
For typical neutron star masses and using optical observations of the
carbon/oxygen-core white dwarf we derive a mass range for the companion of . We apply evolutionary white dwarf cooling
models to revisit the cooling age of the companion. Our analysis reveals that
the companion has an effective temperature of K and a
cooling age of Gyr, which is roughly a factor of three
lower than the pulsar's characteristic age of 10.4 Gyr. The cooling age implies
an initial spin period of ms, which is very close to the current
period.Comment: 11 pages, 5 figures, accepted for publication in A&
Palomar Gattini-IR: Survey overview, data processing system, on-sky performance and first results
Palomar Gattini-IR is a new wide-field, near-infrared (NIR) robotic time domain survey operating at Palomar Observatory. Using a 30 cm telescope mounted with a H2RG detector, Gattini-IR achieves a field of view (FOV) of 25 sq. deg. with a pixel scale of 8.”7 in J-band. Here, we describe the system design, survey operations, data processing system and on-sky performance of Palomar Gattini-IR. As a part of the nominal survey, Gattini-IR scans ≈7500 square degrees of the sky every night to a median 5σ depth of 15.7 AB mag outside the Galactic plane. The survey covers ≈15,000 square degrees of the sky visible from Palomar with a median cadence of 2 days. A real-time data processing system produces stacked science images from dithered raw images taken on sky, together with point-spread function (PSF)-fit source catalogs and transient candidates identified from subtractions within a median delay of ≈4 hr from the time of observation. The calibrated data products achieve an astrometric accuracy (rms) of ≈0.”7 with respect to Gaia DR2 for sources with signal-to-noise ratio > 10, and better than ≈0.”35 for sources brighter than ≈12 Vega mag. The photometric accuracy (rms) achieved in the PSF-fit source catalogs is better than ≈3% for sources brighter than ≈12 Vega mag and fainter than the saturation magnitude of ≈8.5 Vega mag, as calibrated against the Two Micron All Sky Survey catalog. The detection efficiency of transient candidates injected into the images is better than 90% for sources brighter than the 5σ limiting magnitude. The photometric recovery precision of injected sources is 3% for sources brighter than 13 mag, and the astrometric recovery rms is ≈0.”9. Reference images generated by stacking several field visits achieve depths of ≳16.5 AB mag over 60% of the sky, while it is limited by confusion in the Galactic plane. With a FOV ≈40× larger than any other existing NIR imaging instrument, Gattini-IR is probing the reddest and dustiest transients in the local universe such as dust obscured supernovae in nearby galaxies, novae behind large columns of extinction within the galaxy, reddened microlensing events in the Galactic plane and variability from cool and dust obscured stars. We present results from transients and variables identified since the start of the commissioning period
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