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 $q=2.06$ 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 $\sim10^{-2}M_\odot$ 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 $(1,2,3)$, which we scale to a redshifted total mass of $80M_\odot$ and luminosity distance of $400$ Mpc. For each of these mass ratios, we consider signals with eccentricities of $\sim0.05$ and $\sim 0.1$ at $17$ 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 $\sim 90\%$ credibility at a distance of $\gtrsim 1.5$ 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