7,060 research outputs found
Nano-Hertz Gravitational Waves Searches with Interferometric Pulsar Timing Experiments
We estimate the sensitivity to nano-Hertz gravitational waves of pulsar
timing experiments in which two highly-stable millisecond pulsars are tracked
simultaneously with two neighboring radio telescopes that are referenced to the
same time-keeping subsystem (i.e. "the clock"). By taking the difference of the
two time-of-arrival residual data streams we can exactly cancel the clock noise
in the combined data set, thereby enhancing the sensitivity to gravitational
waves. We estimate that, in the band () Hz, this
"interferometric" pulsar timing technique can potentially improve the
sensitivity to gravitational radiation by almost two orders of magnitude over
that of single-telescopes. Interferometric pulsar timing experiments could be
performed with neighboring pairs of antennas of the forthcoming large arraying
projects.Comment: Paper submitted to Phys. Rev. Letters. It is 9 pages long, and
includes 2 figure
From Equivalence Principles to Cosmology: Cosmic Polarization Rotation, CMB Observation, Neutrino Number Asymmetry, Lorentz Invariance and CPT
In this paper, we review the approach leading to cosmic polarization rotation
observation and present the current status with an outlook. In the study of the
relations among equivalence principles, we found that long-range
pseudoscalar-photon interaction is allowed. Pseudoscalar-photon interaction
would induce a rotation of linear polarization of electromagnetic wave
propagating with cosmological/astrophysical distance. In 2002, DASI
successfully observed the polarization of the cosmological microwave background
radiation. In 2003, WMAP observed the correlation of polarization with
temperature anisotropy at more than 10 sigma in the cosmological microwave
background. From this high polarization-temperature correlation in WMAP
observation, we put a limit of 0.1 rad on the rotation of linear polarization
of cosmological microwave background (CMB) propagation. Pseudoscalar-photon
interaction is proportional to the gradient of the pseudoscalar field. From
phenomenological point of view, this gradient could be neutrino number
asymmetry current, other density current, or a constant vector. In these
situations, Lorentz invariance or CPT may or may not effectively be violated.
In this paper, we review and compile various results. Better accuracy in CMB
polarization observation is expected from PLANCK mission to be launched next
year. A dedicated CMB polarization observer in the future would probe this
fundamental issue more deeply.Comment: 9 pages, 2 figures, a few references with corresponding text change
added in this version, invited talk given in VIII Asia-Pacific International
Conference on Gravitation and Astophysics (ICGA8), August 29 - September 1,
2007, Nara Women's University, Japan, submitted to Progress of Theoretical
Physics Supplemen
Plasmonic crystals for ultrafast nanophotonics: Optical switching of surface plasmon polaritons
We demonstrate that the dispersion of surface plasmon polaritons in a
periodically perforated gold film can be efficiently manipulated by femtosecond
laser pulses with the wavelengths far from the intrinsic resonances of gold.
Using a time- and frequency- resolved pump-probe technique we observe shifting
of the plasmon polariton resonances with response times from 200 to 800 fs
depending on the probe photon energy, through which we obtain comprehensive
insight into the electron dynamics in gold. We show that Wood anomalies in the
optical spectra provide pronounced resonances in differential transmission and
reflection with magnitudes up to 3% for moderate pump fluences of 0.5 mJ/cm^2.Comment: 5 pages, 4 figure
Strong fields and neutral particle magnetic moment dynamics
Interaction of magnetic moment of point particles with external
electromagnetic fields experiences unresolved theoretical and experimental
discrepancies. In this work we point out several issues within the relativistic
quantum mechanics and the QED and we describe effects related to a new
covariant classical model of magnetic moment dynamics. Using this framework we
explore the invariant acceleration experienced by neutral particles coupled to
an external plane wave field through the magnetic moment: we study the case of
ultra relativistic Dirac neutrinos with magnetic moment in the range of
to ; and we address the case of slowly
moving neutrons. We explore how critical accelerations for neutrinos can be
experimentally achieved in laser-pulse interactions. The radiation of
accelerated neutrinos can serve as an important test distinguishing between
Majorana and Dirac nature of neutrinos.Comment: 8 page
On generation of Crab giant pulses
We propose that Crab giant pulses are generated on closed magnetic field
lines near the light cylinder via anomalous cyclotron resonance on the ordinary
mode. Waves are generated in a set of fine, unequally spaced, narrow emission
bands at frequencies much lower than a local cyclotron frequency. Location of
emission bands is fitted to spectral structures seen by Eilek et al. (2006).
To reproduce the data, the required density of plasma in the giant pulses
emission region is much higher, by a factor , than the
minimal Goldreich-Julian density. Emission is generated by a population of
highly energetic particles with radiation-limited Lorentz factors , produced during occasional reconnection close to the Y point,
where the last closed field lines approach the light cylinder.Comment: accepted by MNRAS; added estimate of simultaneous GLAST signa
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