2,003 research outputs found
Intersecting Jones projections
Let M be a von Neumann algebra on a Hilbert space H with a cyclic and
separating unit vector \Omega and let \omega be the faithful normal state on M
given by \omega(\cdot)=(\Omega,\cdot\Omega). Moreover, let {N_i :i\in I} be a
family of von Neumann subalgebras of M with faithful normal conditional
expectations E_i of M onto N_i satisfying \omega=\omega\circ E_i for all i\in I
and let N=\bigcap_{i\in I} N_i. We show that the projections e_i, e of H onto
the closed subspaces \bar{N_i\Omega} and \bar{N\Omega} respectively satisfy
e=\bigwedge_{i\in I}e_i.This proves a conjecture of V.F.R. Jones and F. Xu in
\cite{JonesXu04}
Constraint violation in free evolution schemes: comparing BSSNOK with a conformal decomposition of Z4
We compare numerical evolutions performed with the BSSNOK formulation and a
conformal decomposition of a Z4-like formulation of General Relativity. The
important difference between the two formulations is that the Z4 formulation
has a propagating Hamiltonian constraint, whereas BSSNOK has a zero-speed
characteristic variable in the constraint subsystem. In spherical symmetry we
evolve both puncture and neutron star initial data. We demonstrate that the
propagating nature of the Z4 constraints leads to results that compare
favorably with BSSNOK evolutions, especially when matter is present in the
spacetime. From the point of view of implementation the new system is a simple
modification of BSSNOK.Comment: Published in PR
A 1.2V 10μW NPN-Based Temperature Sensor in 65nm CMOS with an inaccuracy of ±0.2°C (3s) from −70°C to 125°C
This paper describes a temperature sensor realized in a 65nm CMOS process with a batch-calibrated inaccuracy of ±0.5°C (3σ) and a trimmed inaccuracy of ±0.2°C (3σ) from –70°C to 125°C. This represents a 10-fold improvement in accuracy compared to other deep-submicron temperature sensors [1,2], and is comparable with that of state-of-the-art sensors implemented in larger-featuresize processes [3,4]. The sensor draws 8.3μA from a 1.2V supply and occupies an area of 0.1mm2, which is 45 times less than that of sensors with comparable accuracy [3,4]. These advances are enabled by the use of NPN transistors as sensing elements, the use of dynamic techniques i.e. correlated double sampling (CDS) and dynamic element matching (DEM), and a single room-temperature trim
A 2.4GHz 830pJ/bit duty-cycled wake-up receiver with −82dBm sensitivity for crystal-less wireless sensor nodes
A 65 nm CMOS 2.4 GHz wake-up receiver operating with low-accuracy frequency references has been realized. Robustness to frequency inaccuracy is achieved by employing non-coherent energy detection, broadband-IF heterodyne architecture and impulse-radio modulation. The radio dissipates 415 ¿W at 500 kb/s and achieves a sensitivity of -82 dBm with an energy efficiency of 830 pJ/bit.\u
Binary black hole merger in the extreme-mass-ratio limit: a multipolar analysis
Building up on previous work, we present a new calculation of the
gravitational wave (GW) emission generated during the transition from
quasi-circular inspiral to plunge, merger and ringdown by a binary system of
nonspinning black holes, of masses and , in the extreme mass ratio
limit, . The relative dynamics of the system is computed
{\it without making any adiabatic approximation} by using an effective one body
(EOB) description, namely by representing the binary by an effective particle
of mass moving in a (quasi-)Schwarzschild background of
mass and submitted to an \O(\nu) 5PN-resummed analytical
radiation reaction force, with . The gravitational wave emission is
calculated via a multipolar Regge-Wheeler-Zerilli type perturbative approach
(valid in the limit ). We consider three mass ratios,
,and we compute the multipolar waveform up to
. We estimate energy and angular momentum losses during the
quasi-universal and quasi-geodesic part of the plunge phase and we analyze the
structure of the ringdown. We calculate the gravitational recoil, or "kick",
imparted to the merger remnant by the gravitational wave emission and we
emphasize the importance of higher multipoles to get a final value of the
recoil . We finally show that there is an {\it excellent
fractional agreement} () (even during the plunge) between the 5PN
EOB analytically-resummed radiation reaction flux and the numerically computed
gravitational wave angular momentum flux. This is a further confirmation of the
aptitude of the EOB formalism to accurately model extreme-mass-ratio inspirals,
as needed for the future space-based LISA gravitational wave detector.Comment: 20 pages, 12 figures. Version published in Phys. Rev.
Deriving relativistic momentum and energy. II. Three-dimensional case
We generalise a recent derivation of the relativistic expressions for
momentum and kinetic energy from the one-dimensional to the three-dimensional
case.Comment: 7 page
Gravitational waves from pulsations of neutron stars described by realistic Equations of State
In this work we discuss the time-evolution of nonspherical perturbations of a
nonrotating neutron star described by a realistic Equation of State (EOS). We
analyze 10 different EOS for a large sample of neutron star models. Various
kind of generic initial data are evolved and the corresponding gravitational
wave signals are computed. We focus on the dynamical excitation of fluid and
spacetime modes and extract the corresponding frequencies. We employ a
constrained numerical algorithm based on standard finite differencing schemes
which permits stable and long term evolutions. Our code provides accurate
waveforms and allows to capture, via Fourier analysis of the energy spectra,
the frequencies of the fluid modes with an accuracy comparable to that of
frequency domain calculations. The results we present here are useful for
provindig comparisons with simulations of nonlinear oscillations of (rotating)
neutron star models as well as testbeds for 3D nonlinear codes.Comment: 17 pages, 9 figures. Small changes. Version published in Phys. Rev.
Experimental study on the creep behavior of GFRP pultruded beams
The objective of the paper is to explore the validity of the Time-Temperature-Stress Superposition Principle (TTSSP) to describe the creep behaviour of glass fibre reinforced polymer (GFRP) pultruded beams. For this purpose, an experimental programme, including both short- and long-term creep tests, has been carried out. A total of twenty pultruded GFRP beams have been tested in a 4-point bending scheme. Tests have been conducted at controlled room temperature (26°C, 32°C, 41°C) and prescribed percentage of the ultimate load (26%, 35%, 45%). Findley’s law has been used to interpret the results of the short-term experiments. Then, the TTSSP has been applied to build a master curve, usable to predict the results of long-term experiments. The results demonstrate the extent of validity of the TTSSP for predicting the creep behaviour of GFRP composites, at least for the material used and the duration of the tests
Deontic justice and organizational neuroscience
According to deontic justice theory, individuals often feel principled moral obligations to uphold norms of justice. That is, standards of justice can be valued for their own sake, even apart from serving self-interested goals. While a growing body of evidence in business ethics supports the notion of deontic justice, skepticism remains. This hesitation results, at least in part, from the absence of a coherent framework for explaining how individuals produce and experience deontic justice. To address this need, we argue that a compelling, yet still missing, step is to gain further understanding into the underlying neural and psychological mechanisms of deontic justice. Here, we advance a theoretical model that disentangles three key processes of deontic justice: The use of justice rules to assess events, cognitive empathy, and affective empathy. Together with reviewing neural systems supporting these processes, broader implications of our model for business ethics scholarship are discussed
Dynamical excitation of space-time modes of compact objects
We discuss, in the perturbative regime, the scattering of Gaussian pulses of
odd-parity gravitational radiation off a non-rotating relativistic star and a
Schwarzschild Black Hole. We focus on the excitation of the -modes of the
star as a function of the width of the pulse and we contrast it with the
outcome of a Schwarzschild Black Hole of the same mass. For sufficiently narrow
values of , the waveforms are dominated by characteristic space-time modes.
On the other hand, for sufficiently large values of the backscattered
signal is dominated by the tail of the Regge-Wheeler potential, the
quasi-normal modes are not excited and the nature of the central object cannot
be established. We view this work as a useful contribution to the comparison
between perturbative results and forthcoming -mode 3D-nonlinear numerical
simulation.Comment: RevTeX, 9 pages, 7 figures, Published in Phys. Rev.
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