40 research outputs found
Uncertainty principle for proper time and mass
We review Bohr's reasoning in the Bohr-Einstein debate on the photon box
experiment. The essential point of his reasoning leads us to an uncertainty
relation between the proper time and the rest mass of the clock. It is shown
that this uncertainty relation can be derived if only we take the fundamental
point of view that the proper time should be included as a dynamic variable in
the Lagrangian describing the system of the clock. Some problems and some
positive aspects of our approach are then discussed.Comment: 15 pages, accepted for publication in J. Math. Phy
Association of mid-infrared solar plages with Calcium K line emissions and magnetic structures
Solar mid-IR observations in the 8-15 micrometer band continuum with moderate
angular resolution (18 arcseconds) reveal the presence of bright structures
surrounding sunspots. These plage-like features present good association with
calcium CaII K1v plages and active region magnetograms. We describe a new
optical setup with reflecting mirrors to produce solar images on the focal
plane array of uncooled bolometers of a commercial camera preceded by germanium
optics. First observations of a sunspot on September 11, 2006 show a mid-IR
continuum plage exhibiting spatial distribution closely associated with CaII
K1v line plage and magnetogram structures. The mid-IR continuum bright plage is
about 140 K hotter than the neighboring photospheric regions, consistent with
hot plasma confined by the magnetic spatial structures in and above the active
regionComment: 5 pages, 4 figures. Accepted by PAS
Comparison of 30 THz impulsive burst time development to microwaves, H-alpha, EUV, and GOES soft X-rays
The recent discovery of impulsive solar burst emission in the 30 THz band is
raising new interpretation challenges. One event associated with a GOES M2
class flare has been observed simultaneously in microwaves, H-alpha, EUV, and
soft X-ray bands. Although these new observations confirm some features found
in the two prior known events, they exhibit time profile structure
discrepancies between 30 THz, microwaves, and hard X-rays (as inferred from the
Neupert effect). These results suggest a more complex relationship between 30
THz emission and radiation produced at other wavelength ranges. The multiple
frequency emissions in the impulsive phase are likely to be produced at a
common flaring site lower in the chromosphere. The 30 THz burst emission may be
either part of a nonthermal radiation mechanism or due to the rapid thermal
response to a beam of high-energy particles bombarding the dense solar
atmosphere.Comment: accepted to Astronomy and Astrophysic
A bright impulsive solar burst detected at 30 THz
Ground- and space-based observations of solar flares from radio wavelengths
to gamma-rays have produced considerable insights but raised several unsolved
controversies. The last unexplored wavelength frontier for solar flares is in
the range of submillimeter and infrared wavelengths. Here we report the
detection of an intense impulsive burst at 30 THz using a new imaging system.
The 30 THz emission exhibited remarkable time coincidence with peaks observed
at microwave, mm/submm, visible, EUV and hard X-ray wavelengths. The emission
location coincides with a very weak white-light feature, and is consistent with
heating below the temperature minimum in the atmosphere. However, there are
problems in attributing the heating to accelerated electrons. The peak 30 THz
flux is several times larger than the usual microwave peak near 9 GHz,
attributed to non-thermal electrons in the corona. The 30 THz emission could be
consistent with an optically thick spectrum increasing from low to high
frequencies. It might be part of the same spectral component found at sub-THz
frequencies whose nature remains mysterious. Further observations at these
wavelengths will provide a new window for flare studies.Comment: 9 pages, 11 figures, accepted by Astrophysical Journal, March 23,
201
Exponential behavior of a quantum system in a macroscopic medium
An exponential behavior at all times is derived for a solvable dynamical
model in the weak-coupling, macroscopic limit. Some implications for the
quantum measurement problem are discussed, in particular in connection with
dissipation.Comment: 8 pages, report BA-TH/94-17
Macroscopic limit of a solvable dynamical model
The interaction between an ultrarelativistic particle and a linear array made
up of two-level systems (^^ ^^ AgBr" molecules) is studied by making use of
a modified version of the Coleman-Hepp Hamiltonian. Energy-exchange processes
between the particle and the molecules are properly taken into account, and the
evolution of the total system is calculated exactly both when the array is
initially in the ground state and in a thermal state. In the macroscopic limit
(), the system remains solvable and leads to interesting
connections with the Jaynes-Cummings model, that describes the interaction of a
particle with a maser. The visibility of the interference pattern produced by
the two branch waves of the particle is computed, and the conditions under
which the spin array in the limit behaves as a ^^ ^^
detector" are investigated. The behavior of the visibility yields good insights
into the issue of quantum measurements: It is found that, in the
thermodynamical limit, a superselection-rule space appears in the description
of the (macroscopic) apparatus. In general, an initial thermal state of the ^^
^^ detector" provokes a more substantial loss of quantum coherence than an
initial ground state. It is argued that a system decoheres more as the
temperature of the detector increases. The problem of ^^ ^^ imperfect
measurements" is also shortly discussed.Comment: 30 pages, report BA-TH/93-13
Bright 30 THz Impulsive Solar Bursts
Impulsive 30 THz continuum bursts have been recently observed in solar
flares, utilizing small telescopes with a unique and relatively simple optical
setup concept. The most intense burst was observed together with a GOES X2
class event on October 27, 2014, also detected at two sub-THz frequencies,
RHESSI X-rays and SDO/HMI and EUV. It exhibits strikingly good correlation in
time and in space with white light flare emission. It is likely that this
association may prove to be very common. All three 30 THz events recently
observed exhibited intense fluxes in the range of 104 solar flux units,
considerably larger than those measured for the same events at microwave and
sub-mm wavelengths. The 30 THz burst emission might be part of the same
spectral burst component found at sub-THz frequencies. The 30 THz solar bursts
open a promising new window for the study of flares at their originComment: 11 pages, 4 Figures J. Geophys. Res - Space Physics, accepted, May
21, 201
Terahertz photometer to observe solar flares in continuum
Solar observations at sub-THz frequencies detected a new flare spectral
component peaking in the THz range, simultaneously with the well known
microwaves component, bringing challenging constraints for interpretation.
Higher THz frequencies observations are needed to understand the nature of the
mechanisms occurring in flares. A THz photometer system was developed to
observe outside the terrestrial atmosphere on stratospheric balloons or
satellites, or at exceptionally transparent ground stations. The telescope was
designed to observe the whole solar disk detecting small relative changes in
input temperature caused by flares at localized positions. A Golay cell
detector is preceded by low-pass filters to suppress visible and near IR
radiation, a band-pass filter, and a chopper. A prototype was assembled to
demonstrate the new concept and the system performance. It can detect
temperature variations smaller than 1 K for data sampled at a rate of
10/second, smoothed for intervals larger than 4 seconds. For a 76 mm aperture,
this corresponds to small solar burst intensities at THz frequencies. A system
with 3 and 7 THz photometers is being built for solar flare observations on
board of stratospheric balloon missions.Comment: 11 pages, 8 figures, accepted by Journal of Infrared, Millimeter, and
Terahertz Waves, 9 December 201
Factorization in the model of unstable particles with continuous masses
We study processes with unstable particles in intermediate time-like states.
It is shown that the amplitudes squared of such processes factor exactly in the
framework of the model of unstable particles with continuous masses. Decay
widths and cross sections can then be represented in a universal factorized
form for an arbitrary set of interacting particles. This exact factorization is
caused by specific structure of propagators in the model. We formulate the
factorization method and perform a phenomenological analysis of the
factorization effects. The factorization method considerably simplifies
calculations while leading to compact and reasonable results.Comment: 20 pages, 6 figure
Raman spectroscopy as a tool to study TiC formation during controlled ball milling
Titanium and carbon elemental powder mixtures with compositions of Ti100âxCx (x=50,40,30) were milled under a helium atmosphere using a magnetoball mill. For Ti50C50 and Ti60C40 powder mixtures, the combined results of external mill temperature monitoring and x-ray diffraction (XRD) analysis indicated that, after a specific incubation period, titanium carbide (TiC) was formed rapidly via a highly exothermic mechanically induced reaction. However, contrary to the current understanding of mechanically induced self-propagating reactions, Raman spectroscopy clearly showed the formation of nonstoichiometric TiC in Ti50C50 and Ti60C40 powders prior to the sudden exothermic event occurring inside the mill. This result has not been reported in previous studies that used only XRD analysis to characterize the as-milled powders. It is now thought that a significant component of the heat generated after the incubation period may be due to a combination of rapid grain growth and/or recrystallization of the preexisting TiC, rather than the direct formation of TiC. When milling Ti70C30, the reaction to form TiC proceeded gradually as milling progressed