28 research outputs found
Mirror World, Supersymmetric Axion and Gamma Ray Bursts
A modification of the relation between axion mass and the PQ constant permits
a relaxation of the astrophysical constraints, considerably enlarging the
allowed axion parameter space. We develop this idea in this paper, discussing a
model for an {\it ultramassive} axion, which essentially represents a
supersymmetric Weinberg-Wilczek axion of the mirror world. The experimental and
astrophysical limits allow a PQ scale f_a ~ 10^4-10^6 GeV and a mass m_a ~
1MeV, which can be accessible for future experiments.
On a phenomenological ground, such an {\it ultramassive} axion turns out to
be quite interesting. It can be produced during the gravitational collapse or
during the merging of two compact objects, and its subsequent decay into e+e-
provides an efficient mechanism for the transfer of the gravitational energy of
the collapsing system to the electron-positron plasma. This could resolve the
energy budget problem in the Gamma Ray Bursts and also help in understanding
the SN type II explosion phenomena.Comment: 20 pages, 5 eps figures, added footnote and reference
The Atmospheric Chemistry Suite (ACS) of Three Spectrometers for the ExoMars 2016 Trace Gas Orbiter
The Atmospheric Chemistry Suite (ACS) package is an element of the Russian contribution to the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission. ACS consists of three separate infrared spectrometers, sharing common mechanical, electrical, and thermal interfaces. This ensemble of spectrometers has been designed and developed in response to the Trace Gas Orbiter mission objectives that specifically address the requirement of high sensitivity instruments to enable the unambiguous detection of trace gases of potential geophysical or biological interest. For this reason, ACS embarks a set of instruments achieving simultaneously very high accuracy (ppt level), very high resolving power (>10,000) and large spectral coverage (0.7 to 17 ÎŒmâthe visible to thermal infrared range). The near-infrared (NIR) channel is a versatile spectrometer covering the 0.7â1.6 ÎŒm spectral range with a resolving power of âŒ20,000. NIR employs the combination of an echelle grating with an AOTF (Acousto-Optical Tunable Filter) as diffraction order selector. This channel will be mainly operated in solar occultation and nadir, and can also perform limb observations. The scientific goals of NIR are the measurements of water vapor, aerosols, and dayside or night side airglows. The mid-infrared (MIR) channel is a cross-dispersion echelle instrument dedicated to solar occultation measurements in the 2.2â4.4 ÎŒm range. MIR achieves a resolving power of >50,000. It has been designed to accomplish the most sensitive measurements ever of the trace gases present in the Martian atmosphere. The thermal-infrared channel (TIRVIM) is a 2-inch double pendulum Fourier-transform spectrometer encompassing the spectral range of 1.7â17 ÎŒm with apodized resolution varying from 0.2 to 1.3 cmâ1. TIRVIM is primarily dedicated to profiling temperature from the surface up to âŒ60 km and to monitor aerosol abundance in nadir. TIRVIM also has a limb and solar occultation capability. The technical concept of the instrument, its accommodation on the spacecraft, the optical designs as well as some of the calibrations, and the expected performances for its three channels are described
Big Bang Baryogenesis
An overview of baryogenesis in the early Universe is presented. The standard
big bang model including big bang nucleosynthesis and inflation is breifly
reviewed. Three basic models for baryogenesis will be developed: The
``standard" out-of-equilibrium decay model; the decay of scalar consensates
along flat directions in supersymmetric models; and lepto-baryogenesis, which
is the conversion of a lepton asymmetry into a baryon asymmetry via
non-perturbative electroweak interactions.Comment: 36 pages, LaTeX, UMN-TH-1249, Lectures given at the 33rd
International Winter School on Nuclear and Particle Physics, ``Matter Under
Extreme Conditions", Feb. 27 - March 5 1994, Schladming Austri
Investigations of the Mars Upper Atmosphere with ExoMars Trace Gas Orbiter
The Martian mesosphere and thermosphere, the region above about 60 km, is not the primary target of the ExoMars 2016 mission but its Trace Gas Orbiter (TGO) can explore it and address many interesting issues, either in-situ during the aerobraking period or remotely during the regular mission. In the aerobraking phase TGO peeks into thermospheric densities and temperatures, in a broad range of latitudes and during a long continuous period. TGO carries two instruments designed for the detection of trace species, NOMAD and ACS, which will use the solar occultation technique. Their regular sounding at the terminator up to very high altitudes in many different molecular bands will represent the first time that an extensive and precise dataset of densities and hopefully temperatures are obtained at those altitudes and local times on Mars. But there are additional capabilities in TGO for studying the upper atmosphere of Mars, and we review them briefly. Our simulations suggest that airglow emissions from the UV to the IR might be observed outside the terminator. If eventually confirmed from orbit, they would supply new information about atmospheric dynamics and variability. However, their optimal exploitation requires a special spacecraft pointing, currently not considered in the regular operations but feasible in our opinion. We discuss the synergy between the TGO instruments, specially the wide spectral range achieved by combining them. We also encourage coordinated operations with other Mars-observing missions capable of supplying simultaneous measurements of its upper atmosphere
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Water Vapor Vertical Profiles on Mars in Dust Storms Observed by TGO/NOMAD
It has been suggested that dust storms efficiently transport water vapor from the nearâsurface to the middle atmosphere on Mars. Knowledge of the water vapor vertical profile during dust storms is important to understand water escape. During Martian Year 34, two dust storms occurred on Mars: a global dust storm (June to midâSeptember 2018) and a regional storm (January 2019). Here we present water vapor vertical profiles in the periods of the two dust storms (Ls = 162â260° and Ls = 298â345°) from the solar occultation measurements by Nadir and Occultation for Mars Discovery (NOMAD) onboard ExoMars Trace Gas Orbiter (TGO). We show a significant increase of water vapor abundance in the middle atmosphere (40â100 km) during the global dust storm. The water enhancement rapidly occurs following the onset of the storm (Ls~190°) and has a peak at the most active period (Ls~200°). Water vapor reaches very high altitudes (up to 100 km) with a volume mixing ratio of ~50 ppm. The water vapor abundance in the middle atmosphere shows high values consistently at 60°Sâ60°N at the growth phase of the dust storm (Ls = 195°â220°), and peaks at latitudes greater than 60°S at the decay phase (Ls = 220°â260°). This is explained by the seasonal change of meridional circulation: from equinoctial Hadley circulation (two cells) to the solstitial one (a single poleâtoâpole cell). We also find a conspicuous increase of water vapor density in the middle atmosphere at the period of the regional dust storm (Ls = 322â327°), in particular at latitudes greater than 60°S