26,364 research outputs found
Comment on Experiments Related to the Aharonov-Bohm Phase Shift
Recent experiments undertaken by Caprez, Barwick, and Batelaan should clarify
the connections between classical and quantum theories in connection with the
Aharonov-Bohm phase shift. It is pointed out that resistive aspects for the
solenoid current carriers play a role in the classical but not the quantum
analysis for the phase shift. The observed absence of a classical lag effect
for a macroscopic solenoid does not yet rule out the possibility of a lag
explanation of the observed phase shift for a microscopic solenoid.Comment: 9 page
Blackbody Radiation and the Scaling Symmetry of Relativistic Classical Electron Theory with Classical Electromagnetic Zero-Point Radiation
It is pointed out that relativistic classical electron theory with classical
electromagnetic zero-point radiation has a scaling symmetry which is suitable
for understanding the equilibrium behavior of classical thermal radiation at a
spectrum other than the Rayleigh-Jeans spectrum. In relativistic classical
electron theory, the masses of the particles are the only scale-giving
parameters associated with mechanics while the action-angle variables are scale
invariant. The theory thus separates the interaction of the action variables of
matter and radiation from the scale-giving parameters. Classical zero-point
radiation is invariant under scattering by the charged particles of
relativistic classical electron theory. The basic ideas of the matter
-radiation interaction are illustrated in a simple relativistic classical
electromagnetic example.Comment: 18 page
The Blackbody Radiation Spectrum Follows from Zero-Point Radiation and the Structure of Relativistic Spacetime in Classical Physics
The analysis of this article is entirely within classical physics. Any
attempt to describe nature within classical physics requires the presence of
Lorentz-invariant classical electromagnetic zero-point radiation so as to
account for the Casimir forces between parallel conducting plates at low
temperatures. Furthermore, conformal symmetry carries solutions of Maxwell's
equations into solutions. In an inertial frame, conformal symmetry leaves
zero-point radiation invariant and does not connect it to non-zero-temperature;
time-dilating conformal transformations carry the Lorentz-invariant zero-point
radiation spectrum into zero-point radiation and carry the thermal radiation
spectrum at non-zero temperature into thermal radiation at a different
non-zero-temperature. However, in a non-inertial frame, a time-dilating
conformal transformation carries classical zero-point radiation into thermal
radiation at a finite non-zero-temperature. By taking the no-acceleration
limit, one can obtain the Planck radiation spectrum for blackbody radiation in
an inertial frame from the thermal radiation spectrum in an accelerating frame.
Here this connection between zero-point radiation and thermal radiation is
illustrated for a scalar radiation field in a Rindler frame undergoing
relativistic uniform proper acceleration through flat spacetime in two
spacetime dimensions. The analysis indicates that the Planck radiation spectrum
for thermal radiation follows from zero-point radiation and the structure of
relativistic spacetime in classical physics.Comment: 21 page
Complex Physics in Cluster Cores: Showstopper for the Use of Clusters for Cosmology?
The influence of cool galaxy cluster cores on the X-ray
luminosity--gravitational mass relation is studied with Chandra observations of
64 clusters in the HIFLUGCS sample. As preliminary results we find (i) a
significant offset of cool core (CC) clusters to the high luminosity (or low
mass) side compared to non-cool core (NCC) clusters, (ii) a smaller scatter of
CC clusters compared to NCC clusters, (iii) a decreasing fraction of CC
clusters with increasing cluster mass, (iv) a reduced scatter in the
luminosity--mass relation for the entire sample if the luminosity is scaled
properly with the central entropy. The implications of these results on the
intrinsic scatter are discussed.Comment: 6 pages; to appear in the proceedings of the conference Heating vs.
Cooling in Galaxies and Clusters of Galaxies, edited by H. Boehringer, P.
Schuecker, G.W. Pratt, and A. Finoguenov. Dedicated to the memory of Peter
Schuecke
Rural Nonfarm Employment Under Trade Reform Evidence From Vietnam, 1993-2002
Vietnam?s rural economy has substantially diversified over the past two decades. The rural nonfarm sector has grown rapidly and became an important source of employment and income for rural households. This growing nonfarm employment was associated with radical changes in the trade policy reform that has put the country to the top two or three performers in the developing world. This paper examines the potential effect of the trade policy reform on nonfarm employment in rural Vietnam during the period 1993-2002. It proposes two trade openness indices that allow changes in the trade policy at the macro level to be transmitted to rural households. The results reveal that the trade policy reform does have a material impact on rural nonfarm employment. While a more liberalized agricultural sector encourages nonfarm diversification, a lower protection level in the nonfarm sector discourages individual participation in nonfarm income-generating activities.Trade liberalization, trade policy reform, rural nonfarm employment, Vietnam
Space-Time Trellis and Space-Time Block Coding Versus Adaptive Modulation and Coding Aided OFDM for Wideband Channels
Abstract—The achievable performance of channel coded spacetime trellis (STT) codes and space-time block (STB) codes transmitted over wideband channels is studied in the context of schemes having an effective throughput of 2 bits/symbol (BPS) and 3 BPS. At high implementational complexities, the best performance was typically provided by Alamouti’s unity-rate G2 code in both the 2-BPS and 3-BPS scenarios. However, if a low complexity implementation is sought, the 3-BPS 8PSK space-time trellis code outperfoms the G2 code. The G2 space-time block code is also combined with symbol-by-symbol adaptive orthogonal frequency division multiplex (AOFDM) modems and turbo convolutional channel codecs for enhancing the system’s performance. It was concluded that upon exploiting the diversity effect of the G2 space-time block code, the channel-induced fading effects are mitigated, and therefore, the benefits of adaptive modulation erode. In other words, once the time- and frequency-domain fades of the wideband channel have been counteracted by the diversity-aided G2 code, the benefits of adaptive modulation erode, and hence, it is sufficient to employ fixed-mode modems. Therefore, the low-complexity approach of mitigating the effects of fading can be viewed as employing a single-transmitter, single-receiver-based AOFDM modem. By contrast, it is sufficient to employ fixed-mode OFDM modems when the added complexity of a two-transmitter G2 scheme is affordable
Coastal resources management in Indonesia: legal and institutional aspects
Fishery management, Natural resources, Fishery policies, Resource conservation, Governments, Resource management, Indonesia,
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