4,304 research outputs found
A Tighter Test of Local Lorentz Invariance using PSR J2317+1439
Gravity being a long-range force, one might {\it a priori} expect the
Universe's global matter distribution to select a preferred rest frame for
local gravitational physics. The phenomenology of preferred-frame effects, in
the strong-gravitational field context of binary pulsars, is described by two
parameters and . These parameters vanish
identically in general relativity, and reduce, in the weak-field limit, to the
two parametrized post-Newtonian (PPN) parameters and .
We derive a limit of (90\%~C.L.) using
the very low eccentricity binary pulsar PSR J2317+1439, improving by a factor
of 3 on previous limits.Comment: 4 pages, LaTeX, requires aaspp4.sty and flushrt.sty, submitted to Ap
Out of the frying pan: a young pulsar with a long radio trail emerging from SNR G315.9-0.0
The faint radio supernova remnant SNR G315.9-0.0 is notable for a long and
thin trail that extends outward perpendicular from the edge of its
approximately circular shell. In a search with the Parkes telescope we have
found a young and energetic pulsar that is located at the tip of this
collimated linear structure. PSR J1437-5959 has period P = 61 ms,
characteristic age tau_c = 114 kyr, and spin-down luminosity dE/dt = 1.4e36
erg/s. It is very faint, with a flux density at 1.4 GHz of about 75 uJy. From
its dispersion measure of 549 pc/cc, we infer d ~ 8 kpc. At this distance and
for an age comparable to tau_c, the implied pulsar velocity in the plane of the
sky is V_t = 300 km/s for a birth at the center of the SNR, although it is
possible that the SNR/pulsar system is younger than tau_c and that V_t > 300
km/s. The highly collimated linear feature is evidently the pulsar wind trail
left from the supersonic passage of PSR J1437-5959 through the interstellar
medium surrounding SNR G315.9-0.0.Comment: accepted for publication in ApJ Letter
Evolution of complexity following a quantum quench in free field theory
Using a recent proposal of circuit complexity in quantum field theories
introduced by Jefferson and Myers, we compute the time evolution of the
complexity following a smooth mass quench characterized by a time scale in a free scalar field theory. We show that the dynamics has two distinct
phases, namely an early regime of approximately linear evolution followed by a
saturation phase characterized by oscillations around a mean value. The
behavior is similar to previous conjectures for the complexity growth in
chaotic and holographic systems, although here we have found that the
complexity may grow or decrease depending on whether the quench increases or
decreases the mass, and also that the time scale for saturation of the
complexity is of order (not parametrically larger).Comment: V2: added references, new plots, and improved discussion of results
on Section 5, V3: Few minor corrections. Published versio
Momentum-space entanglement after smooth quenches
We compute the total amount of entanglement produced between momentum modes
at late times after a smooth mass quench in free bosonic and fermionic quantum
field theories. The entanglement and R\'enyi entropies are obtained in closed
form as a function of the parameters characterizing the quench protocol. For
bosons, we show that the entanglement production is more significant for light
modes and for fast quenches. In particular, infinitely slow or adiabatic
quenches do not produce any entanglement. Depending on the quench profile, the
decrease as a function of the quench rate can be either monotonic or
oscillating. In the fermionic case the situation is subtle and there is a
critical value for the quench amplitude above which this behavior is changed
and the entropies become peaked at intermediate values of momentum and of the
quench rate. We also show that the results agree with the predictions of a
Generalized Gibbs Ensemble and obtain explicitly its parameters in terms of the
quench data.Comment: 24 pages, 8 Figures; V2 matches published versio
Discovery of the energetic pulsar J1747-2809 in the supernova remnant G0.9+0.1
The supernova remnant G0.9+0.1 has long been inferred to contain a central
energetic pulsar. In observations with the NRAO Green Bank Telescope at 2 GHz,
we have detected radio pulsations from PSR J1747-2809. The pulsar has a
rotation period of 52 ms, and a spin-down luminosity of 4.3e37 erg/s, the
second largest among known Galactic pulsars. With a dispersion measure of 1133
pc/cc, PSR J1747-2809 is distant, at ~13 kpc according to the NE2001 electron
density model, although it could be located as close as the Galactic center.
The pulse profile is greatly scatter-broadened at a frequency of 2 GHz, so that
it is effectively undetectable at 1.4 GHz, and is very faint, with
period-averaged flux density of 40 uJy at 2 GHz.Comment: minor changes from v1 - matches published versio
Timing of pulsars found in a deep Parkes multibeam survey
We have carried out a sensitive radio pulsar survey along the northern
Galactic plane ( and |b| \lapp 2^{\circ}) using
the Parkes 20-cm multibeam system. We observed each position for 70-min on two
separate epochs. Our analyses to date have so far resulted in the detection of
32 pulsars, of which 17 were previously unknown. Here we summarize the
observations and analysis and present the timing observations of 11 pulsars and
discovery parameters for a further 6 pulsars. We also present a timing solution
for the 166-ms bursting pulsar, PSR~J1938+2213, previously discovered during an
Arecibo drift-scan survey. Our survey data for this pulsar show that the
emission can be described by a steady pulse component with bursting emission,
which lasts for typically 20--25 pulse periods, superposed. Other new
discoveries are the young 80.1-ms pulsar PSR~J1935+2025 which exhibits a
significant amount of unmodeled low-frequency noise in its timing residuals,
and the 4.2-ms pulsar PSR~J1935+1726 which is in a low-mass binary system with
a 90.7-day circular orbit.Comment: 6 pages, 2 figures, accepted for publication in MNRA
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