563 research outputs found
Toward an understanding of short distance repulsions among baryons in QCD -- NBS wave functions and operator product expansion --
We report on our recent attempts to determine the short distance behaviors of
general 2-baryon and 3-baryon forces, which are defined from the
Nambu-Bethe-Salpeter(NBS) wave function, by using the operator product
expansion and a renormalization group analysis in QCD. We have found that the
repulsion at short distance increases as the number of valence quarks increases
or when the number of different flavors involved decreases. This global
tendency suggests a Pauli suppression principle among quark fields at work.Comment: 14 pages, add two exmples in sect.3.4, a version accepted for
Progress of Theoretical Physic
A broadband radio study of the average profile and giant pulses from PSR B1821-24A
We present the results of wide-band (720-2400 MHz) study of PSR B1821-24A
(J1824-2452A, M28A), an energetic millisecond pulsar visible in radio, X-rays
and gamma-rays. In radio, the pulsar has a complex average profile which spans
>85% of the spin period and exhibits strong evolution with observing frequency.
For the first time we measure phase-resolved polarization properties and
spectral indices of radio emission throughout almost all of the on-pulse
window. We combine this knowledge with the high-energy information to compare
M28A to other known gamma-ray millisecond pulsars and to speculate that M28A's
radio emission originates in multiple regions within its magnetosphere (i.e.
both in the slot or outer gaps near the light cylinder and at lower altitudes
above the polar cap). M28A is one of the handful of pulsars which are known to
emit Giant Pulses (GPs) -- short, bright radio pulses of unknown nature. We
report a drop in the linear polarization of the average profile in both windows
of GP generation and also a `W'-shaped absorption feature (resembling a double
notch), partly overlapping with one of the GP windows. The GPs themselves have
broadband spectra consisting of multiple patches with fractional spectral width
() of about 0.07. Although our time resolution was not
sufficient to resolve the GP structure on the microsecond scale, we argue that
GPs from this pulsar most closely resemble the GPs from the main pulse of the
Crab pulsar, which consist of a series of narrowband nanoshots.Comment: 16 pages, 8 figures, accepted to Ap
Green Bank Telescope Observations of the Eclipse of Pulsar "A" in the Double Pulsar Binary PSR J0737-3039
We report on the first Green Bank Telescope observations at 427, 820 and 1400
MHz of the newly discovered, highly inclined and relativistic double pulsar
binary. We focus on the brief eclipse of PSR J0737-3039A, the faster pulsar,
when it passes behind PSR J0737-3039B. We measure a frequency-averaged eclipse
duration of 26.6 +/- 0.6 s, or 0.00301 +/- 0.00008 in orbital phase. The
eclipse duration is found to be significantly dependent on radio frequency,
with eclipses longer at lower frequencies. Specifically, eclipse duration is
well fit by a linear function having slope (-4.52 +/- 0.03) x 10^{-7}
orbits/MHz. We also detect significant asymmetry in the eclipse. Eclipse
ingress takes 3.51 +/- 0.99 times longer than egress, independent of radio
frequency. Additionally, the eclipse lasts (40 +/- 7) x 10^{-5} in orbital
phase longer after conjunction, also independent of frequency. We detect
significant emission from the pulsar on short time scales during eclipse in
some orbits. We discuss these results in the context of a model in which the
eclipsing material is a shock-heated plasma layer within the slower PSR
J0737-3039B's light cylinder, where the relativistic pressure of the faster
pulsar's wind confines the magnetosphere of the slower pulsar.Comment: 12 pages, 3 figure
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