7 research outputs found
Constraining the dense matter equation-of-state with radio pulsars
Radio pulsars provide some of the most important constraints for our
understanding of matter at supranuclear densities. So far, these constraints
are mostly given by precision mass measurements of neutron stars (NS). By
combining single measurements of the two most massive pulsars, J03480432 and
J07406620, the resulting lower limit of 1.98 (99% confidence) of
the maximum NS mass, excludes a large number of equations of state (EOSs).
Further EOS constraints, complementary to other methods, are likely to come
from the measurement of the moment of inertia (MOI) of binary pulsars in
relativistic orbits. The Double Pulsar, PSR J07373039A/B, is the most
promising system for the first measurement of the MOI via pulsar timing.
Reviewing this method, based in particular on the first MeerKAT observations of
the Double Pulsar, we provide well-founded projections into the future by
simulating timing observations with MeerKAT and the SKA. For the first time, we
account for the spin-down mass loss in the analysis. Our results suggest that
an MOI measurement with 11% accuracy (68% confidence) is possible by 2030. If
by 2030 the EOS is sufficiently well known, however, we find that the Double
Pulsar will allow for a 7% test of Lense-Thirring precession, or alternatively
provide a -measurement of the next-to-leading order gravitational
wave damping in GR. Finally, we demonstrate that potential new discoveries of
double NS systems with orbital periods shorter than that of the Double Pulsar
promise significant improvements in these measurements and the constraints on
NS matter.Comment: 13 pages, 8 figures. Accepted by MNRA
The PyCBC search for gravitational waves from compact binary coalescence
We describe the PyCBC search for gravitational waves from compact-object
binary coalescences in advanced gravitational-wave detector data. The search
was used in the first Advanced LIGO observing run and unambiguously identified
two black hole binary mergers, GW150914 and GW151226. At its core, the PyCBC
search performs a matched-filter search for binary merger signals using a bank
of gravitational-wave template waveforms. We provide a complete description of
the search pipeline including the steps used to mitigate the effects of noise
transients in the data, identify candidate events and measure their statistical
significance. The analysis is able to measure false-alarm rates as low as one
per million years, required for confident detection of signals. Using data from
initial LIGO's sixth science run, we show that the new analysis reduces the
background noise in the search, giving a 30% increase in sensitive volume for
binary neutron star systems over previous searches.Comment: 29 pages, 7 figures, accepted by Classical and Quantum Gravit
Single-neuron mechanisms of neural adaptation in the human temporal lobe
Abstract A central function of the human brain is to adapt to new situations based on past experience. Adaptation is reflected behaviorally by shorter reaction times to repeating or similar stimuli, and neurophysiologically by reduced neural activity in bulk-tissue measurements with fMRI or EEG. Several potential single-neuron mechanisms have been hypothesized to cause this reduction of activity at the macroscopic level. We here explore these mechanisms using an adaptation paradigm with visual stimuli bearing abstract semantic similarity. We recorded intracranial EEG (iEEG) simultaneously with spiking activity of single neurons in the medial temporal lobes of 25 neurosurgical patients. Recording from 4917 single neurons, we demonstrate that reduced event-related potentials in the macroscopic iEEG signal are associated with a sharpening of single-neuron tuning curves in the amygdala, but with an overall reduction of single-neuron activity in the hippocampus, entorhinal cortex, and parahippocampal cortex, consistent with fatiguing in these areas