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Supermassive black holes (SMBHs) merging in dwarf galaxies will be detectable by the Laser Interferometer Space Antenna (LISA) in the mid-2030s. Previous cosmological hydrodynamic simulations have shown the prediction of massive black holes merging in dwarf galaxies, but these simulations are limited by their resolution and cannot follow black hole pairs all the way to coalescence. We calculate the delay time between black hole pairing and merger based on the properties of the black holes and their host galaxies, and use these properties to calculate gravitational wave strains for eleven different binary black holes that merge inside dwarf galaxies from eight cosmological simulations. This delay time calculation accounts for dynamical friction due to gas and stars, loss-cone scattering, and hardening of the binary due to gravitational radiation. Out of the eleven black hole mergers in the simulations, five black hole pairs will merge within 0.8 - 8 Gyr of forming a close pair and could be observed by LISA, and the remaining six are unresolved due to resolution limitations of the simulation. As all five of the resolved close pairs merge within a Hubble time, we make the broad estimate that close SMBH pairs in dwarf galaxies will merge and be detectable by LISA, but this estimate depends on either the presence of gas during orbital decay or a solution to the dynamical buoyancy problem in cored potentials., 8 pages, 3 figures

The analysis of gravitational wave (GW) datasets is based on the comparison of measured time series with theoretical templates of the detector's response to a variety of source parameters. For LISA, the main scientific observables will be the so-called time-delay interferometry (TDI) combinations, which suppress the otherwise overwhelming laser noise. Computing the TDI response to GW involves projecting the GW polarizations onto the LISA constellation arms, and then combining projections delayed by a multiple of the light propagation time along the arms. Both computations are difficult to perform efficiently for generic LISA orbits and GW signals. Various approximations are currently used in practice, e.g., assuming constant and equal armlengths, which yields analytical TDI expressions. In this article, we present 'fastlisaresponse', a new efficient GPU-accelerated code that implements the generic TDI response to GWs in the time domain. We use it to characterize the parameter-estimation bias incurred by analyzing loud Galactic-binary signals using the equal-armlength approximation. We conclude that equal-armlength parameter-estimation codes should be upgraded to the generic response if they are to achieve optimal accuracy for high (but reasonable) SNR sources within the actual LISA data., Comment: 15 pages, 7 figures, 2 tables

The current generation of all-sky surveys is rapidly expanding our ability to study variable and transient sources. These surveys, with a variety of sensitivities, cadences, and fields of view, probe many ranges of time-scale and magnitude. Data from the Zwicky Transient Facility (ZTF) yields an opportunity to find variables on time-scales from minutes to months. In this paper, we present the codebase, ztfperiodic, and the computational metrics employed for the catalogue based on ZTF’s Second Data Release. We describe the publicly available, graphical-process-unit optimized period-finding algorithms employed, and highlight the benefit of existing and future graphical-process-unit clusters. We show how generating metrics as input to catalogues of this scale is possible for future ZTF data releases. Further work will be needed for future data from the Vera C. Rubin Observatory’s Legacy Survey of Space and Time.

The Laser Interferometer Space Antenna (LISA) will detect and characterize ∼104 Galactic Binaries, consisting predominantly of two white dwarfs (WDs). An interesting prospect within this population is a third object – another WD star, a circumbinary exoplanet (CBP), or a brown dwarf (BD) – in orbit about the inner WD pair. We present the first fully Bayesian detection and posterior analysis of substellar objects with LISA, focusing on the characterization of CBPs. We used an optimistic astrophysically motivated catalogue of these CBP third-body sources, including their orbital eccentricity around the inner binary for the first time. We examined Bayesian evidence computations for detectability, as well as the effects on the posterior distributions for both the inner binary parameters and the third-body parameters. We find that the posterior behaviour bifurcates based on whether the third-body period is above or below half the observation time. Additionally, we find that undetectable third-body sources can bias the inner binary parameters whether or not the correct template is used. We used the information retrieved from the study of the CBP population to make an initial conservative prediction for the number of detectable BD systems in the original catalogue. We end with commentary on the predicted qualitative effects on LISA global fitting and Galactic Binary population analysis. The procedure used in this work is generic and can be directly applied to other astrophysical effects expected within the Galactic Binary population. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society., VK acknowledges support from the Netherlands Research Council NWO (Rubicon 019.183EN.015 grant). NK acknowledges the support from the Gr-PRODEX 2019 funding program (PEA 4000132310). This research was supported in part through the computational resources and staff contributions provided for the Quest/Grail high-performance computing facility at Northwestern University. NT acknowledges support form the French space agency CNES in the framework of LISA. CD acknowledges financial support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709), and the Group project Ref. PID2019-110689RB-I00/AEI/10.13039/501100011033. This work was supported by the COST action CA16104 ‘Gravitational waves, black holes, and fundamental physics’ (GWverse) through a Short-Term Scientific Mission (STSM) awarded to CD (ID 48268) and VK (ID 48272). COST actions are supported by COST (European Cooperation in Science and Technology). NJC appreciates the support of the NASA LISA Foundation Science grant 80NSSC19K0320. This project has received financial support from the CNRS through the MITI interdisciplinary programs. This paper also employed the use of SCIPY (Jones et al. 2001) and MATPLOTLIB (Hunter 2007).

We compute adiabatic waveforms for extreme mass-ratio inspirals (EMRIs) by "stitching" together a long inspiral waveform from a sequence of waveform snapshots, each of which corresponds to a particular geodesic orbit. We show that the complicated total waveform can be regarded as a sum of "voices." Each voice evolves in a simple way on long timescales, a property which can be exploited to efficiently produce waveform models that faithfully encode the properties of EMRI systems. We look at examples for a range of different orbital geometries: spherical orbits, equatorial eccentric orbits, and one example of generic (inclined and eccentric) orbits. To our knowledge, this is the first calculation of a generic EMRI waveform that uses strong-field radiation reaction. We examine waveforms in both the time and frequency domains. Although EMRIs evolve slowly enough that the stationary phase approximation (SPA) to the Fourier transform is valid, the SPA calculation must be done to higher order for some voices, since their instantaneous frequency can change from chirping forward ($\dot f > 0$) to chirping backward ($\dot f < 0$). The approach we develop can eventually be extended to more complete EMRI waveform models, for example to include effects neglected by the adiabatic approximation such as the conservative self force and spin-curvature coupling., 31 pages, 17 figures. Update: corrected a sign error in a term in Eq. (B5). This factor was correct in the related code, it was purely a typo in the manuscript. An erratum to PRD has been submitted. Many thanks to Angelica Albertini for bringing this error to our attention

Since 2015 the gravitational-wave observations of LIGO and Virgo have transformed our understanding of compact-object binaries. In the years to come, ground-based gravitational-wave observatories such as LIGO, Virgo, and their successors will increase in sensitivity, discovering thousands of stellar-mass binaries. In the 2030s, the space-based LISA will provide gravitational-wave observations of massive black holes binaries. Between the $\sim 10$-$10^3~\mathrm{Hz}$ band of ground-based observatories and the $\sim10^{-4}$-$10^{-1}~\mathrm{Hz}$ band of LISA lies the uncharted decihertz gravitational-wave band. We propose a Decihertz Observatory to study this frequency range, and to complement observations made by other detectors. Decihertz observatories are well suited to observation of intermediate-mass ($\sim10^2$-$10^4 M_\odot$) black holes; they will be able to detect stellar-mass binaries days to years before they merge, providing early warning of nearby binary neutron star mergers and measurements of the eccentricity of binary black holes, and they will enable new tests of general relativity and the Standard Model of particle physics. Here we summarise how a Decihertz Observatory could provide unique insights into how black holes form and evolve across cosmic time, improve prospects for both multimessenger astronomy and multiband gravitational-wave astronomy, and enable new probes of gravity, particle physics and cosmology., Comment: 13 pages, 1 figure. Published in Experimental Astronomy. Summarising white paper arXiv:1908.11375

We examine the effects of merger and merger policy on a potential entrant’s pre-merger product choice. We establish conditions under which the possibility of merger can induce an entrant to inefficiently imitate an incumbent’s product instead of innovating with a more differentiated product. Turning to policy, current practice is to evaluate a proposed merger by focusing on post-merger effects (e.g., whether the merged firm will charge higher prices or invest less in innovation than would the two firms if they remained independent of one another). We show that policies focused solely on a proposed merger’s ex post welfare effects can induce an entrant to choose an inefficient direction for its pre-merger investment decisions. We also show that, taking into account merger policy’s effects on pre-merger product choice, it can be optimal to approve mergers with a positive probability even when the post-merger welfare effects of every consummated merger are negative.

The future space mission LISA will observe a wealth of gravitational-wave sources at millihertz frequencies. Of these, the extreme-mass-ratio inspirals of compact objects into massive black holes are the only sources that combine the challenges of strong-field complexity with that of long-lived signals. Such signals are found and characterized by comparing them against a large number of accurate waveform templates during data analysis, but the rapid generation of such templates is hindered by computing the $\sim10^3$-$10^5$ harmonic modes in a fully relativistic waveform. We use order-reduction and deep-learning techniques to derive a global fit for these modes, and implement it in a complete waveform framework with hardware acceleration. Our high-fidelity waveforms can be generated in under $1\,\mathrm{s}$, and achieve a mismatch of $\lesssim 5\times 10^{-4}$ against reference waveforms that take $\gtrsim 10^4$ times longer. This marks the first time that analysis-length waveforms with full harmonic content can be produced on timescales useful for direct implementation in LISA analysis algorithms., 6 pages, 3 figures

Many inspiraling and merging stellar remnants emit both gravitational and electromagnetic radiation as they orbit or collide. These gravitational wave events together with their associated electromagnetic counterparts provide insight about the nature of the merger, allowing us to further constrain properties of the binary. With the future launch of the Laser Interferometer Space Antenna (LISA), follow up observations and models are needed of ultracompact binary (UCB) systems. Current and upcoming long baseline time domain surveys will observe many of these UCBs. We present a new fast periodic object search tool capable of searching for generic periodic signals based on the Conditional Entropy algorithm. This new implementation allows for a grid search over both the period ($P$) and the time derivative of the period ($\dot{P}$). To demonstrate the usage of this tool, we use a small, hand-picked subset of a UCB population generated from the population synthesis code \cosmic, as well as a custom catalog for varying periods at fixed intrinsic parameters. We simulate light curves as likely to be observed by future time domain surveys by using an existing eclipsing binary light curve model accounting for the change in orbital period due to gravitational radiation. We find that a search with $\dot{P}$ values is necessary for detecting binaries at orbital periods less than $\sim$10 min. We also show it is useful in finding and characterizing binaries with longer periods, but at a higher computational cost. Our code is called gce (GPU-Accelerated Conditional Entropy). It is available at https://github.com/mikekatz04/gce., 15 pages, 7 figures

Commentators on both the right and the left ends of the political spectrum have called for new and more forceful approaches to antitrust enforcement with respect to large multisided platforms: especially Amazon, Facebook, and Google. In part, these calls have been driven by the fact that these platforms have business models that make extensive use of data about their users. This article surveys what economics has to say about a wide range of antitrust issues—including the treatment of exclusionary conduct, merger, and privacy—that are raised by multisided platforms’ reliance on big data collected about their users.

Although the economics of multisided platforms has developed important insights for antitrust policy, there are critical respects in which the body of academic knowledge falls short of providing useful advice to enforcement agencies and the courts. Indeed, there is a substantial risk that recent scholarship will be misapplied to the detriment of sound antitrust policy, as evidenced by the US Supreme Court's recent decision in American Express. In this note, I identify several areas in which economics research could potentially make significant contributions to the practical antitrust treatment of platforms.

There is broad concern that merger policy toward Big Tech has been too lenient. Big Tech typically operates in markets characterized by innovation-driven “competition for the market.” I show that this fact provides a rationale for heightened scrutiny of incumbents’ acquisitions of emerging or potential competitors. I also address the widespread argument that permissive merger policy promotes innovative entry by facilitating entry for buyout. I show that permissive merger policy can also discourage entrant innovation. One way is by diminishing entrants’ incentives to invest in marginal product improvements when such improvements reduce the gains from merger. A second way is by facilitating incumbency for buyout, under which an incumbent makes investments in order to extract rents from an entrant through merger.

The Laser Interferometer Space Antenna (LISA) is slated for launch in the early 2030s. A main target of the mission is massive black hole binaries that have an expected detection rate of $\sim20$ yr$^{-1}$. We present a parameter estimation analysis for a variety of massive black hole binaries. This analysis is performed with a graphics processing unit (GPU) implementation comprising the phenomhm waveform with higher-order harmonic modes and aligned spins; a fast frequency-domain LISA detector response function; and a GPU-native likelihood computation. The computational performance achieved with the GPU is shown to be 500 times greater than with a similar CPU implementation, which allows us to analyze full noise-infused injections at a realistic Fourier bin width for the LISA mission in a tractable and efficient amount of time. With these fast likelihood computations, we study the effect of adding aligned spins to an analysis with higher-order modes by testing different configurations of spins in the injection, as well as the effect of varied and fixed spins during sampling. Within these tests, we examine three different binaries with varying mass ratios, redshifts, sky locations, and detector-frame total masses ranging over three orders of magnitude. We discuss varied correlations between the total masses and mass ratios; unique spin posteriors for the larger mass binaries; and the constraints on parameters when fixing spins during sampling, allowing us to compare to previous analyses that did not include aligned spins., Comment: 27 pages, 13 figures

Economic research establishes that market power is now a serious problem. Growing market power harms consumers and workers, slows innovation, and limits productivity growth. Market power is on the rise in a number of major industries, including, for example, airlines, brewing, and hospitals, where multiple horizontal mergers that were allowed to proceed without antitrust challenge have markedly increased concentration in important markets and facilitated the exercise of market power. Exclusionary conduct by dominant companies that stifles competition from actual and potential rivals — including nascent rivals with capabilities for challenging a dominant firm’s market power and firms with competing R&D efforts — impairs what is often the most important economic force creating competitive pressure for dominant firms. This concern exists in digital marketplaces. Platforms are often insulated from platform competition to a substantial extent by substantial scale economies in supply and demand (network effects) combined with customer switching costs. Courts have contributed to increased monopoly power through decisions that have weakened the prohibitions against anticompetitive exclusionary conduct and anticompetitive mergers. The antitrust laws, as interpreted and enforced today, are inadequate to confront and deter growing market power in the U.S. economy and unnecessarily limit the ability of antitrust enforcers to address anticompetitive conduct. Many key antitrust precedents — particularly those precedents governing exclusionary conduct — rely on unsound economic theories or unsupported empirical claims about the competitive effects of certain practices. In part for this reason, the antitrust rules constructed by the courts reflect a systematically skewed error cost balance: they are too concerned to avoid both chilling procompetitive conduct and the high costs of litigation, and too dismissive of the costs of failing to deter harmful conduct. Excessively permissive precedents and unsound or unsupported economic claims have, in turn, encouraged overly cautious enforcement policies and overly demanding proof requirements and have discouraged government enforcers and private plaintiffs from bringing meritorious exclusionary conduct cases. The statement discusses a number of legal rules that are unsupported by or inconsistent with sound economic research that have contributed to overly permissive rules. The signatories to this letter strongly believe that antitrust enforcement has become too lax, in large part because of the courts and that Congress must act to correct this problem. The statement suggests a number of reforms could be considered. We do not collectively or unanimously endorse any of these, though some of us have done so in other contexts. We do believe that Congress has a historic opportunity to identify adverse trends in judicial interpretation of the antitrust and correct problems—not just by overriding damaging precedents, but also by reshaping the antitrust laws more broadly to enhance deterrence of anticompetitive conduct.

The gravitational-wave astronomical revolution began in 2015 with LIGO's observation of the coalescence of two stellar-mass black holes. Over the coming decades, ground-based detectors like LIGO will extend their reach, discovering thousands of stellar-mass binaries. In the 2030s, the space-based LISA will enable gravitational-wave observations of the massive black holes in galactic centres. Between LISA and ground-based observatories lies the unexplored decihertz gravitational-wave frequency band. Here, we propose a Decihertz Observatory to cover this band, and complement observations made by other gravitational-wave observatories. The decihertz band is uniquely suited to observation of intermediate-mass ($\sim 10^2$-$10^4 M_\odot$) black holes, which may form the missing link between stellar-mass and massive black holes, offering a unique opportunity to measure their properties. Decihertz observations will be able to detect stellar-mass binaries days to years before they merge and are observed by ground-based detectors, providing early warning of nearby binary neutron star mergers, and enabling measurements of the eccentricity of binary black holes, providing revealing insights into their formation. Observing decihertz gravitational-waves also opens the possibility of testing fundamental physics in a new laboratory, permitting unique tests of general relativity and the Standard Model of particle physics. Overall, a Decihertz Observatory will answer key questions about how black holes form and evolve across cosmic time, open new avenues for multimessenger astronomy, and advance our understanding of gravitation, particle physics and cosmology., 52 pages, 5 figures, 4 tables. Submitted to Classical & Quantum Gravity. Based upon a white paper for ESA's Voyage 2050 on behalf of the LISA Consortium 2050 Task Force

Massive black hole binaries (MBHBs) of $10^5 \, \rm M_\odot - 3 \times 10^7 \, \rm M_\odot $ merging in low redshift galaxies ($z\le4$) are sufficiently loud to be detected weeks before coalescence with the Laser Interferometer Space Antenna (LISA). This allows us to perform the parameter estimation $on$ $the$ $fly$, i.e. as a function of the time to coalescence during the inspiral phase, relevant for early warning of the planned LISA protected periods and for searches of electromagnetic signals. In this work, we study the evolution of the sky position, luminosity distance, chirp mass and mass ratio uncertainties as function of time left before merger. Overall, light systems with total intrinsic mass $\rm M_{\rm tot} = 3 \times 10^5 \, \rm M_\odot$ are characterized by smaller uncertainties than heavy ones ($\rm M_{\rm tot} = 10^7 \, \rm M_\odot$) during the inspiral. Luminosity distance, chirp mass and mass ratio are well constrained at the end of the inspiral. Concerning sky position, at $z=1$, MBHBs with $\rm M_{\rm tot} = 3 \times 10^5 \, \rm M_\odot$ can be localized with a median precision of $\simeq 10^2 \, \rm deg^2 (\simeq 1 \, \rm deg^2)$ at 1 month (1 hour) from merger, while the sky position of heavy MBHBs can be determined to $10 \, \rm deg^2$ only 1 hour before merger. However the uncertainty around the median values broadens with time, ranging in between 0.04 -- 20 $\rm deg^2$ (0.3 -- 3 $\times 10^3 \, \rm deg^2$) for light (heavy) systems at 1 hour before merger. At merger the sky localization improves down to $\simeq 10^{-1} \, \rm deg^2$ for all masses. For the benefit of the observer community, we provide the full set of data from our simulations and simple and ready-to-use analytical fits to describe the time evolution of uncertainties in the aforementioned parameters, valid for systems with total mass between $10^5$--$10^7 \, \rm M_\odot$ and redshift $0.3$--$3$., Comment: 31 pages, 24 figures and 6 tables. Accepted for publication in Physical Review D

ESA and NASA are moving forward with plans to launch LISA around 2034. With data from the Illustris cosmological simulation, we provide analysis of LISA detection rates accompanied by characterization of the merging massive black hole population. Massive black holes of total mass $\sim10^5-10^{10} M_\odot$ are the focus of this study. We evolve Illustris massive black hole mergers, which form at separations on the order of the simulation resolution ($\sim$kpc scales), through coalescence with two different treatments for the binary massive black hole evolutionary process. The coalescence times of the population, as well as physical properties of the black holes, form a statistical basis for each evolutionary treatment. From these bases, we Monte Carlo synthesize many realizations of the merging massive black hole population to build mock LISA detection catalogs. We analyze how our massive black hole binary evolutionary models affect detection rates and the associated parameter distributions measured by LISA. With our models, we find massive black hole binary detection rates with LISA of $\sim0.5-1$ yr$^{-1}$ for massive black holes with masses greater than $10^5M_\odot$. This should be treated as a lower limit primarily because our massive black hole sample does not include masses below $10^5M_\odot$, which may significantly add to the observed rate. We suggest reasons why we predict lower detection rates compared to much of the literature., 18 pages, 9 figures, 3 tables

I examine the (lack of) economic logic that underlies the U.S. Federal Communications Commission’s latest iteration of network neutrality regulations. I explore potential unintended consequences and find a substantial tension between the regulations and the objective of promoting consumer choice and sovereignty. I also identify market developments that could largely neutralize the regulations unless they are expanded to constrain Internet access providers’ actions further.

We correct and clarify the results of Gans (J Regul Econ 47:183–200, 2015) regarding the effects of net neutrality regulation on equilibrium outcomes in settings where a content provider sells its services to consumers for a fee. We examine both pricing and investment effects. We extend the earlier paper’s result that weak forms of net neutrality are ineffective and also show that even a strong form of net neutrality may be ineffective. In addition, we demonstrate that, when strong net neutrality does affect the equilibrium outcome, it may harm efficiency by distorting both ISP and content provider investment and service-quality choices.

There is broad concern that merger policy toward Big Tech has been too lenient. Big Tech typically operates in markets characterized by innovation-driven “competition for the market.” I show that this fact provides a rationale for heightened scrutiny of incumbents’ acquisitions of emerging or potential competitors. I also address the widespread argument that permissive merger policy promotes innovative entry by facilitating entry for buyout. I show that permissive merger policy can also discourage entrant innovation. One way is by diminishing entrants’ incentives to invest in marginal product improvements when such improvements reduce the gains from merger. A second way is by facilitating incumbency for buyout, under which an incumbent makes investments in order to extract rents from an entrant through merger.

We conduct an analysis of the measurement abilities of distinctive LISA detector designs, examining the influence of LISA's low-frequency performance on the detection and characterization of massive black hole binaries. We are particularly interested in LISA's ability to measure massive black holes merging at frequencies near the low-frequency band edge, with masses in the range of $\sim 10^6-10^{10}M_\odot$. We examine the signal-to-noise ratio (SNR) using phenomenological waveforms for inspiral, merger, and ringdown over a wide range of massive black hole binary parameters. We employ a broad palette of possible LISA configurations with different sensitivities at low frequencies. For this analysis, we created a tool (github.com/mikekatz04/BOWIE) that evaluates the change in SNR between two parameterized situations. The shifts in SNR are computed as gains or losses as a function of binary parameters, and graphically displayed across a two dimensional grid of parameter values. We illustrate the use of this technique for both parameterized LISA mission designs, as well as for considering the influence of astrophysical parameters on gravitational wave signal models. In terms of low-frequency sensitivity, acceleration noise or armlength is found to be the most important factor in observing the largest massive black hole binaries, followed by break frequency and then spectral index. LISA's ability to probe the astrophysical population of $\sim10^7-10^9M_\odot$ black holes is greatly influenced by these aspects of its sensitivity. The importance of the constituent black hole spins is also highlighted., 11 pages, 6 figures

The distinction between complements, substitutes, and independent goods is important in many contexts. It is well known that when consumers’ conditional indirect utilities for two goods are superadditive, the goods are gross complements. Generalizing insights in Gans and King (2006) and Gentzkow (2007), we show that superadditivity between one pair of goods can also introduce complementarity between competing pairs of goods. One implication is that lower prices can result from a merger between producers of goods that themselves offer no superadditivity.

Multisided platforms are ubiquitous in today’s economy. Although newspapers demonstrate that the platform business model is scarcely new, recent economic analysis has explored more deeply the manner of its operation. Drawing upon these insights, we conclude that enforcers and courts should use a multiple-markets approach in which different groups of users on different sides of a platform belong in different product markets. This approach appropriately accounts for cross-market network effects without collapsing all of a platform’s users into a single product market. Furthermore, we advocate the use of a separate-effects analysis, which rejects the view that anticompetitive conduct harming users on one side of a platform can be justified so long as that harm funds benefits for users on another side. Courts should consider the price structure, and not simply the net price, of a platform in assessing competitive effects. This approach in turn supports our final conclusion: that antitrust plaintiffs should not be required to prove as part of their prima facie case more than occurrence of competitive harm in a properly-defined market; thereafter, the burden to produce procompetitive justifications should shift to defendants.

The dynamical processing of black holes in the dense cores of globular clusters (GCs), makes them efficient factories for producing binary black holes (BBHs). Here we explore the population of BBHs that form dynamically in GCs and may be observable at mHz frequencies or higher with LISA. We use our Monte Carlo stellar dynamics code, which includes gravitational radiation reaction effects for all BH encounters. By creating a representative local universe of GCs, we show that up to dozens of these systems may be resolvable by LISA with signal-to-noise ratios of at least 5. Approximately one third of these binaries will have measurable eccentricities ($e > 10^{-3}$) in the LISA band and a small number ($\lesssim 5$) may evolve from the LISA band to the LIGO band during the LISA mission., Accepted for publication in Physical Review D

Public and private entities around the world are trying to induce the provision of higher-quality health care by adopting institutional arrangements intended to promote competition among care providers. I selectively survey and supplement the literature to show that an increase in competition—modeled either as a larger number of care providers or greater precision of signals available to consumers regarding provider quality—may result in lower equilibrium quality, holding prices fixed. These findings are an indication that considerable opportunities exist for industrial organization theorists to contribute to our understanding of healthcare markets.

In systems industries, combinations of components are consumed together to generate user benefits. Arrangements among component providers sometimes limit consumers’ ability to mix-and-match components, and such exclusive arrangements have been highly controversial. We examine the competitive and welfare effects of exclusive arrangements among system components in a model of relatively differentiated applications that run on relatively undifferentiated platforms. We show that there is no “One-Market-Power-Rent Theorem.” Specifically, exclusive deals with providers of differentiated applications can raise platforms’ margins without reducing applications’ margins, so that overall industry profits rise. Hence, for a given set of components and prices, exclusive arrangements can reduce consumer welfare by limiting consumer choice and raising equilibrium prices. In some cases, however, exclusivity can raise consumer welfare by increasing the equilibrium number of platforms, which leads to lower prices relative to the monopoly outcome that would prevail absent exclusivity.

When long-term investors trade slowly changing portfolios, they are not particularly sensitive to when they should place or modify their bets. Short-term information can be used to guide investors on how to time their trades. Strategic trade modification provides exposure to short-term signals without imposing additional transaction costs or capacity limits. Long-term investors should not ignore short-term information simply because it is too expensive to trade on.

Both senders and receivers of telecommunications messages derive benefits, creating the possibility of externalities. We explore whether intercarrier compensation (i.e., access charges) can induce carriers to internalize these external effects. In important settings, access charges are irrelevant. Where they are relevant, access charges can induce an efficient ratio of off-net send and receive prices--taking their sum as given--but cannot induce the correct sum. The latter requires a mechanism for cross-carrier internalization, such as repeat play or pricing policies contingent on one another. Lastly, non-zero access charges can be efficient even in highly symmetrical situations.

A large literature demonstrates the empirical importance of internal reference price effects. There are several theories regarding how and why these effects arise. We offer a simple test that distinguishes between the two leading theories based on economically rational behavior: price as a signal of quality and price as a predictor of future prices. Our test builds on differences in how past consumer purchases interact with internal reference prices. We first validate the reliability of our test by applying it to synthetic data. We then apply our test to purchases of ketchup and diapers and find: (1) quality signaling is the dominant mechanism behind reference price effects in both categories; (2) consistent with the quality-signaling theory, reference price effects diminish as various measures of consumer experience increase; but (3) in both categories there are many individuals for whom price-prediction effects dominate quality-signaling effects.

We correct and extend the results of Gans (2015) regarding the effects of net neutrality regulation on equilibrium outcomes in settings where a content provider sells its services to consumers for a fee. We examine both pricing and investment effects. We extend the earlier paper’s result that weak forms of net neutrality are ineffective and also show that even a strong form of net neutrality may be ineffective. In addition, we demonstrate that, when strong net neutrality does affect the equilibrium outcome, it may harm efficiency by distorting both ISP and content provider investment and service-quality choices.

A large literature examines the use of observable and unrenegotiable agency contracts as commitments. These analyses generally impose an ad hoc restriction that contracts cannot be contingent on one another. I relax this restriction and obtain a folk theorem. Unlike earlier folk theorems in this area, the present result applies to agency relationships that have hidden-action problems. Using an example, I also demonstrate that there are settings in which interdependent contracts support a strictly larger set of equilibrium outcomes than do independent contracts. The result highlights the critical need for careful thought about restrictions placed on the set of feasible contracts.

In many markets, including payment cards and telecommunications, service providers operate networks that support customer transactions with each other. When the two sides of a transaction belong to more than one network in common, the question arises as to which network will carry the transaction. We show that the answer depends on a combination of who has the formal authority to choose and the parties' network subscription decisions. Our central finding is that granting formal authority to one side of the market can increase the extent to which transactions run over the network preferred by the other side of the market. We also characterize competing networks' equilibrium choices of routing rules and prices.

There is a long history of governmental efforts to protect personal privacy and strong debates about the merits of such policies. A central element of privacy is the ability to control the dissemination of personally identifiable data to private parties. Posner, Stigler, and others have argued that privacy comes at the expense of allocative efficiency. Others have argued that privacy issues are readily resolved by proper allocation of property rights to control information. Our principal findings challenge both views. We find: (a) privacy can be efficient even when there is no “taste” for privacy per se, and (b) to be effective, a privacy policy may need to ban information transmission or use rather than simply assign individuals control rights to their personally identifiable data.

We explore issues in theory-driven choice modeling by focusing on partial-equilibrium models of dynamic structural demand with forward-looking decision-makers, full equilibrium models that integrate the supply side, integration of bounded rationality in dynamic structural models of choice and public policy implications of these models.

Although network effects can make predation more likely to succeed, we find that the leading anti-predation rules may lower or raise efficiency and consumer welfare in network markets. We find that: (a) the extensive debates about the ‘correct’ measure of cost on which to base price floors are unlikely to be productive; (b) the Ordover-Willig rule that is widely thought to be correct in theory but difficult to apply in practice is, in fact, incorrect in theory; and (c) efficient price floors would have to depend on consumer expectations and coordination processes that are unlikely to be observable in practice.

Merger policy is the most active area of U.S. antitrust policy. It is now widely believed that merger policy must move beyond its traditional focus on static efficiency to account for innovation and address dynamic efficiency. Innovation can fundamentally affect merger analysis in two ways. First, innovation can dramatically affect the relationship between the pre-merger marketplace and what is likely to happen if a proposed merger is consummated. Thus, innovation can fundamentally influence the appropriate analysis for addressing traditional, static efficiency concerns. Second, innovation can itself be an important dimension of market performance that is potentially affected by a merger. We explore how merger policy is meeting the challenges posed by innovation.