4,037 research outputs found
Auctions to gas transmission access: The British experience
When access to monopoly owned networks is constrained auctioning access rights can increase the efficiency of allocations relative to negotiation and grandfathering when there is sufficient competition among network users. Historically, access rights to entry capacity on the British gas network were granted by the monopoly network owner via negotiation; rights were later based on regulated tariffs with an increasing reliance on market based constraint resolution by the system operator. In 1999 an auction mechanism for allocating rights was introduced. Comparing the different allocation methods we conclude that where there is competition at entry terminals auctions have been successful with respect to anticipating spot prices, capturing producer rents and reducing the costs of alleviating network constraints. Moreover, auctions are more transparent and better facilitate entry.gas, network, access, auction, regulation
Improving the NRTidal model for binary neutron star systems
Accurate and fast gravitational waveform (GW) models are essential to extract
information about the properties of compact binary systems that generate GWs.
Building on previous work, we present an extension of the NRTidal model for
binary neutron star (BNS) waveforms. The upgrades are: (i) a new closed-form
expression for the tidal contribution to the GW phase which includes further
analytical knowledge and is calibrated to more accurate numerical relativity
data than previously available; (ii) a tidal correction to the GW amplitude;
(iii) an extension of the spin-sector incorporating equation-of-state-dependent
finite size effects at quadrupolar and octupolar order; these appear in the
spin-spin tail terms and cubic-in-spin terms, both at 3.5PN. We add the new
description to the precessing binary black hole waveform model IMRPhenomPv2 to
obtain a frequency-domain precessing binary neutron star model. In addition, we
extend the SEOBNRv4_ROM and IMRPhenomD aligned-spin binary black hole waveform
models with the improved tidal phase corrections. Focusing on the new
IMRPhenomPv2_NRTidalv2 approximant, we test the model by comparing with
numerical relativity waveforms as well as hybrid waveforms combining tidal
effective-one-body and numerical relativity data. We also check consistency
against a tidal effective-one-body model across large regions of the BNS
parameter space.Comment: Accepted manuscrip
Use of Long-term Auctions for Network Investment
Short-term auctions for access to entry terminals of the British gas-network appear to successfully allocate scarce resources and capture scarcity rent. Now long-term auctions are being introduced to guide future capacity expansion decisions. In our model the fraction of rights issued in the long-term auction turns out to be a crucial design parameter. Even a `hypothetically` optimal parameter choice can in general only satisfy one of three aims: Unbiased provision of capacity, full revelation of private information and minimisation of distortions from network effects. The results suggest that long-term auctions for transmission capacity are not necessarily preferable to regulatory approved capacity expansion.Auctions, Gas, Investment, Networks, Regulation
Binary Neutron Stars with Generic Spin, Eccentricity, Mass ratio, and Compactness - Quasi-equilibrium Sequences and First Evolutions
Information about the last stages of a binary neutron star inspiral and the
final merger can be extracted from quasi-equilibrium configurations and
dynamical evolutions. In this article, we construct quasi-equilibrium
configurations for different spins, eccentricities, mass ratios, compactnesses,
and equations of state. For this purpose we employ the SGRID code, which allows
us to construct such data in previously inaccessible regions of the parameter
space. In particular, we consider spinning neutron stars in isolation and in
binary systems; we incorporate new methods to produce highly eccentric and
eccentricity reduced data; we present the possibility of computing data for
significantly unequal-mass binaries; and we create equal-mass binaries with
individual compactness up to 0.23. As a proof of principle, we explore the
dynamical evolution of three new configurations. First, we simulate a
mass ratio which is the highest mass ratio for a binary neutron star evolved in
numerical relativity to date. We find that mass transfer from the companion
star sets in a few revolutions before merger and a rest mass of
is transferred between the two stars. This configuration
also ejects a large amount of material during merger, imparting a substantial
kick to the remnant. Second, we simulate the first merger of a precessing
binary neutron star. We present the dominant modes of the gravitational waves
for the precessing simulation, where a clear imprint of the precession is
visible in the (2,1) mode. Finally, we quantify the effect of an eccentricity
reduction procedure on the gravitational waveform. The procedure improves the
waveform quality and should be employed in future precision studies, but also
other errors, notably truncation errors, need to be reduced in order for the
improvement due to eccentricity reduction to be effective. [abridged]Comment: (37pages, 26 figures
Effect of Ignoring Eccentricity in Testing General Relativity with Gravitational Waves
Detections of gravitational waves emitted from binary black hole coalescences
allow us to probe the strong-field dynamics of general relativity (GR). One can
compare the observed gravitational-wave signals with theoretical waveform
models to constrain possible deviations from GR. Any physics that is not
included in these waveform models might show up as apparent GR deviations. The
waveform models used in current tests of GR describe binaries on quasicircular
orbits, since most of the binaries detected by ground-based gravitational-wave
detectors are expected to have negligible eccentricities. Thus, a signal from
an eccentric binary in GR is likely to show up as a deviation from GR in the
current implementation of these tests. We study the response of four standard
tests of GR to eccentric binary black hole signals with the forecast O4
sensitivity of the LIGO-Virgo network. Specifically, we consider two
parameterized tests (TIGER and FTI), the modified dispersion relation test, and
the inspiral-merger-ringdown consistency test. To model eccentric signals, we
use non-spinning numerical relativity simulations from the SXS catalog with
three mass ratios , which we scale to a redshifted total mass of
and luminosity distance of Mpc. For each of these mass
ratios, we consider signals with eccentricities of and at
Hz. We find that signals with larger eccentricity lead to very significant
false GR deviations in most tests while signals having smaller eccentricity
lead to significant deviations in some tests. For the larger eccentricity
cases, one would even get a deviation from GR with TIGER at
credibility at a distance of Gpc. Thus, it will be necessary to
exclude the possibility of an eccentric binary in order to make any claim about
detecting a deviation from GR.Comment: 16 pages, 6 figures, version accepted by PR
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