342 research outputs found
High-accuracy comparison of numerical relativity simulations with post-Newtonian expansions
Numerical simulations of 15 orbits of an equal-mass binary black hole system
are presented. Gravitational waveforms from these simulations, covering more
than 30 cycles and ending about 1.5 cycles before merger, are compared with
those from quasi-circular zero-spin post-Newtonian (PN) formulae. The
cumulative phase uncertainty of these comparisons is about 0.05 radians,
dominated by effects arising from the small residual spins of the black holes
and the small residual orbital eccentricity in the simulations. Matching
numerical results to PN waveforms early in the run yields excellent agreement
(within 0.05 radians) over the first cycles, thus validating the
numerical simulation and establishing a regime where PN theory is accurate. In
the last 15 cycles to merger, however, {\em generic} time-domain Taylor
approximants build up phase differences of several radians. But, apparently by
coincidence, one specific post-Newtonian approximant, TaylorT4 at 3.5PN order,
agrees much better with the numerical simulations, with accumulated phase
differences of less than 0.05 radians over the 30-cycle waveform.
Gravitational-wave amplitude comparisons are also done between numerical
simulations and post-Newtonian, and the agreement depends on the post-Newtonian
order of the amplitude expansion: the amplitude difference is about 6--7% for
zeroth order and becomes smaller for increasing order. A newly derived 3.0PN
amplitude correction improves agreement significantly ( amplitude
difference throughout most of the run, increasing to 4% near merger) over the
previously known 2.5PN amplitude terms.Comment: Updated to agree with published version (various minor
clarifications; added description of AH finder in Sec IIB; added discussion
of tidal heating in Sec VC
Recommended from our members
Mathematical deconvolution of CAR T-cell proliferation and exhaustion from real-time killing assay data.
Chimeric antigen receptor (CAR) T-cell therapy has shown promise in the treatment of haematological cancers and is currently being investigated for solid tumours, including high-grade glioma brain tumours. There is a desperate need to quantitatively study the factors that contribute to the efficacy of CAR T-cell therapy in solid tumours. In this work, we use a mathematical model of predator-prey dynamics to explore the kinetics of CAR T-cell killing in glioma: the Chimeric Antigen Receptor T-cell treatment Response in GliOma (CARRGO) model. The model includes rates of cancer cell proliferation, CAR T-cell killing, proliferation, exhaustion, and persistence. We use patient-derived and engineered cancer cell lines with an in vitro real-time cell analyser to parametrize the CARRGO model. We observe that CAR T-cell dose correlates inversely with the killing rate and correlates directly with the net rate of proliferation and exhaustion. This suggests that at a lower dose of CAR T-cells, individual T-cells kill more cancer cells but become more exhausted when compared with higher doses. Furthermore, the exhaustion rate was observed to increase significantly with tumour growth rate and was dependent on level of antigen expression. The CARRGO model highlights nonlinear dynamics involved in CAR T-cell therapy and provides novel insights into the kinetics of CAR T-cell killing. The model suggests that CAR T-cell treatment may be tailored to individual tumour characteristics including tumour growth rate and antigen level to maximize therapeutic benefit
Stable Superstring Relics and Ultrahigh Energy Cosmic Rays
One of the most intriguing experimental results of recent years is the
observation of Ultrahigh Energy Cosmic Rays (UHECRs) above the GZK cutoff.
Plausible candidates for the UHECR primaries are the decay products of a
meta--stable matter state with mass of order O(10^{12-15 GeV}), which
simultaneously is a good cold dark matter candidate. We study possible
meta-stable matter states that arise from Wilson line breaking of GUT
symmetries in semi-realistic heterotic string models. In the models that we
study the exotic matter states can be classified according to patterns of
SO(10) symmetry breaking. We show that cryptons, which are states that carry
fractional electric charge , and are confined by a hidden gauge group
cannot produce viable dark matter. This is due to the fact that, in addition to
the lightest neutral bound state, cryptons give rise to meta-stable charged
bound states. However, these states may still account for the UHECR events. We
argue that the uniton, which is an exotic Standard Model quark but carries
``fractional'' U(1)_{Z'} charge, as well as the singleton, which is a Standard
Model singlet with ``fractional'' U(1)_{Z'} charge do provide viable dark
matter candidates and can at the same time explain the observed UHECR events.Comment: 24 pages. 5 figure
Search for Slowly Moving Magnetic Monopoles with the MACRO Detector
A search for slowly moving magnetic monopoles in the cosmic radiation was conducted from October 1989 to November 1991 using the large liquid scintillator detector subsystem of the first supermodule of the MACRO detector at the Gran Sasso underground laboratory. The absence of candidates established an upper limit on the monopole flux of 5.6 × 10^(−15) cm^(−2) sr^(−1) s^(−1) at 90% confidence level in the velocity range of 10^(−4)≲β<4×10^(−3). This result places a new constraint on the abundance of monopoles trapped in our solar system
Methods to Determine Neutrino Flux at Low Energies:Investigation of the Low Method
We investigate the "low-" method (developed by the CCFR/NUTEV
collaborations) to determine the neutrino flux in a wide band neutrino beam at
very low energies, a region of interest to neutrino oscillations experiments.
Events with low hadronic final state energy (of 1, 2 and 5 GeV)
were used by the MINOS collaboration to determine the neutrino flux in their
measurements of neutrino () and antineutrino (\nub_\mu) total cross
sections. The lowest energy for which the method was used in MINOS is
3.5 GeV, and the lowest \nub_\mu energy is 6 GeV. At these energies, the
cross sections are dominated by inelastic processes. We investigate the
application of the method to determine the neutrino flux for ,
\nub_\mu energies as low as 0.7 GeV where the cross sections are dominated by
quasielastic scattering and (1232) resonance production. We find that
the method can be extended to low energies by using values of 0.25
and 0.50 GeV, which is feasible in fully active neutrino detectors such as
MINERvA.Comment: 25 pages, 32 figures, to be published in European Physics Journal
Search for Nucleon Decays induced by GUT Magnetic Monopoles with the MACRO Experiment
The interaction of a Grand Unification Magnetic Monopole with a nucleon can
lead to a barion-number violating process in which the nucleon decays into a
lepton and one or more mesons (catalysis of nucleon decay). In this paper we
report an experimental study of the effects of a catalysis process in the MACRO
detector. Using a dedicated analysis we obtain new magnetic monopole (MM) flux
upper limits at the level of for
, based on the search for
catalysis events in the MACRO data. We also analyze the dependence of the MM
flux limit on the catalysis cross section.Comment: 12 pages, Latex, 10 figures and 2 Table
A combined analysis technique for the search for fast magnetic monopoles with the MACRO detector
We describe a search method for fast moving ()
magnetic monopoles using simultaneously the scintillator, streamer tube and
track-etch subdetectors of the MACRO apparatus. The first two subdetectors are
used primarily for the identification of candidates while the track-etch one is
used as the final tool for their rejection or confirmation. Using this
technique, a first sample of more than two years of data has been analyzed
without any evidence of a magnetic monopole. We set a 90% CL upper limit to the
local monopole flux of in the
velocity range and for nucleon decay
catalysis cross section smaller than .Comment: 29 pages (12 figures). Accepted by Astroparticle Physic
Final results of magnetic monopole searches with the MACRO experiment
We present the final results obtained by the MACRO experiment in the search
for GUT magnetic monopoles in the penetrating cosmic radiation, for the range
. Several searches with all the MACRO sub-detectors
(i.e. scintillation counters, limited streamer tubes and nuclear track
detectors) were performed, both in stand alone and combined ways. No candidates
were detected and a 90% Confidence Level (C.L.) upper limit to the local
magnetic monopole flux was set at the level of cm
s sr. This result is the first experimental limit obtained in
direct searches which is well below the Parker bound in the whole range
in which GUT magnetic monopoles are expected.Comment: 12 pages, Latex, 9 figures and 2 Table
Muon Energy Estimate Through Multiple Scattering with the Macro Detector
Muon energy measurement represents an important issue for any experiment
addressing neutrino induced upgoing muon studies. Since the neutrino
oscillation probability depends on the neutrino energy, a measurement of the
muon energy adds an important piece of information concerning the neutrino
system. We show in this paper how the MACRO limited streamer tube system can be
operated in drift mode by using the TDC's included in the QTPs, an electronics
designed for magnetic monopole search. An improvement of the space resolution
is obtained, through an analysis of the multiple scattering of muon tracks as
they pass through our detector. This information can be used further to obtain
an estimate of the energy of muons crossing the detector. Here we present the
results of two dedicated tests, performed at CERN PS-T9 and SPS-X7 beam lines,
to provide a full check of the electronics and to exploit the feasibility of
such a multiple scattering analysis. We show that by using a neural network
approach, we are able to reconstruct the muon energy for 40 GeV. The
test beam data provide an absolute energy calibration, which allows us to apply
this method to MACRO data.Comment: 25 pages, 11 figures, Submitted to Nucl. Instr. & Meth.
Nuclearite search with the MACRO detector at Gran Sasso
In this paper we present the results of a search for nuclearites in the
penetrating cosmic radiation using the scintillator and track-etch subdetectors
of the MACRO apparatus. The analyses cover the beta =v/c range at the detector
depth (3700 hg/cm^2) 10^-5 < beta < 1; for beta = 2 x 10^-3 the flux limit is
2.7 x 10^-16 cm^-2 s^-1 sr^-1 for an isotropic flux of nuclearites, and twice
this value for a flux of downgoing nuclearites.Comment: 16 pages, 4 Encapsulated Postscript figures, uses article.sty.
Submitted to The European Physical Journal
- …