14,885 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
MACHO Mass Determination Based on Space Telescope Observation
We investigate the possibility of lens mass determination for a caustic
crossing microlensing event based on a space telescope observation. We
demonstrate that the parallax due to the orbital motion of a space telescope
causes a periodic fluctuation of the light curve, from which the lens distance
can be derived. Since the proper motion of the lens relative to the source is
also measurable for a caustic crossing event, one can find a full solution for
microlensing properties of the event, including the lens mass. To determine the
lens mass with sufficient accuracy, the light curve near the caustic crossing
should be observed within uncertainty of 1%. We argue that the Hubble
Space Telescope observation of the caustic crossing supplied with ground-based
observations of the full light curve will enable us to determine the mass of
MACHOs, which is crucial for understanding the nature of MACHOs.Comment: 9 pages + 3 figures, accepted for publication in ApJ Letter
Nonlocal Effects of Partial Measurements and Quantum Erasure
Partial measurement turns the initial superposition not into a definite
outcome but into a greater probability for it. The probability can approach
100%, yet the measurement can undergo complete quantum erasure. In the EPR
setting, we prove that i) every partial measurement nonlocally creates the same
partial change in the distant particle; and ii) every erasure inflicts the same
erasure on the distant particle's state. This enables an EPR experiment where
the nonlocal effect does not vanish after a single measurement but keeps
"traveling" back and forth between particles. We study an experiment in which
two distant particles are subjected to interferometry with a partial "which
path" measurement. Such a measurement causes a variable amount of correlation
between the particles. A new inequality is formulated for same-angle
polarizations, extending Bell's inequality for different angles. The resulting
nonlocality proof is highly visualizable, as it rests entirely on the
interference effect. Partial measurement also gives rise to a new form of
entanglement, where the particles manifest correlations of multiple
polarization directions. Another novelty in that the measurement to be erased
is fully observable, in contrast to prevailing erasure techniques where it can
never be observed. Some profound conceptual implications of our experiment are
briefly pointed out.Comment: To be published in Phys. Rev. A 63 (2001). 19 pages, 12 figures,
RevTeX 3.
Magnetocaloric effect and improved relative cooling power in (La0.7Sr0.3MnO3/SrRuO3) superlattices
Magnetic properties of a series of (La0.7Sr0.3MnO3/SrRuO3) superlattices,
where the SrRuO3 layer thickness is varying, are examined. A room-temperature
magnetocaloric effect is obtained owing to the finite size effect which reduces
the TC of La0.7Sr0.3MnO3 layers. While the working temperature ranges are
enlarged,, -DeltaSmax values remains similar to the values in polycrystalline
La0.7Sr0.3MnO3. Consequently, the relative cooling powers are significantly
improved, the microscopic mechanism of which is related to the effect of the
interfaces at La0.7Sr0.3MnO3/SrRuO3 and higher nanostructural disorder. This
study indicates that artificial oxide superlattices/multilayers might provide
an alternative pathway in searching for efficient room-temperature magnetic
refrigerators for (nano)microscale systems.Comment: 14^pages, 3 figures, Submitted to J. Phys. Cond. Ma
Induction of Immunological Tolerance to Tissue Allografts with Antilymphocyte Serum
Our interest in the problem of tolerance induction is directly concerned with clinical organ transplantation. ALS is highly effective in depressing cellular immunities. Since at least initial allograft rejection is predominantly a cellular phenomenon, one would expect ALS to be highly effective clinically. Our initial observations in this regard support this concept. However, non-specific depression of cellular immunity may also lead to an increased number or viral, fungal, and protozoan infections. Experiments, such as these presented, strongly suggest that a specific state of tolerance to organ grafts in man should be attainable with the aid of ALS followed by introduction of appropriate antigen
Photoinduced Changes of Reflectivity in Single Crystals of YBa2Cu3O6.5 (Ortho II)
We report measurements of the photoinduced change in reflectivity of an
untwinned single crystal of YBa2Cu3O6.5 in the ortho II structure. The decay
rate of the transient change in reflectivity is found to decrease rapidly with
decreasing temperature and, below Tc, with decreasing laser intensity. We
interpret the decay as a process of thermalization of antinodal quasiparticles,
whose rate is determined by an inelastic scattering rate of quasiparticle
pairs.Comment: 4 pages, 4 figure
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