The bias of the submillimetre galaxy population: SMGs are poor tracers of the most massive structures in the z ~ 2 Universe

It is often claimed that overdensities of (or even individual bright) submillimetre-selected galaxies (SMGs) trace the assembly of the most-massive dark matter structures in the Universe. We test this claim by performing a counts-in-cells analysis of mock SMG catalogues derived from the Bolshoi cosmological simulation to investigate how well SMG associations trace the underlying dark matter structure. We find that SMGs exhibit a relatively complex bias: some regions of high SMG overdensity are underdense in terms of dark matter mass, and some regions of high dark matter overdensity contain no SMGs. Because of their rarity, Poisson noise causes scatter in the SMG overdensity at fixed dark matter overdensity. Consequently, rich associations of less-luminous, more-abundant galaxies (i.e. Lyman-break galaxy analogues) trace the highest dark matter overdensities much better than SMGs. Even on average, SMG associations are relatively poor tracers of the most significant dark matter overdensities because of 'downsizing': at z < ~2.5, the most-massive galaxies that reside in the highest dark matter overdensities have already had their star formation quenched and are thus no longer SMGs. At a given redshift, of the 10 per cent most-massive overdensities, only ~25 per cent contain at least one SMG, and less than a few per cent contain more than one SMG.Comment: 6 pages, 3 figures, 1 table; accepted for publication in MNRAS; minor revisions from previous version, conclusions unchange

Parallel Exclusion

Scholars and courts have long debated whether and when parallel pricing – adoption of the same price by every firm in a market – should be considered a violation of antitrust law. But there has been a comparative neglect of the importance of parallel exclusion – conduct, engaged in by multiple firms, that blocks or slows would-be market entrants. Parallel exclusion merits greater attention, for it can be far more harmful than parallel price elevation. Setting a high price leaves the field open for new entrants and may even attract them. In contrast, parallel action that excludes new entrants both facilitates price elevation and can slow innovation. Reduced innovation has greater long-term significance for the economy. Moreover, parallel exclusion regimes may be more stable than parallel price-elevation regimes. A basic game-theoretic analysis reveals that the factors that leave price elevation vulnerable to breakdown do not apply as strongly to parallel exclusion. Indeed, in some instances, maintaining an exclusion scheme is a dominant strategy for each of the excluders. In such cases, the likelihood of collapse is even lower, yielding a potentially indefinite system of parallel exclusion. This Article proposes the recognition of parallel exclusion as a form of monopolization – subject to the strict limits already present in case law, including monopoly power, anticompetitive effect, and an absence of sufficient procompetitive justification. It also explains why parallel exclusion is a proper concern for merger policy, and why it is bad policy to automatically condemn certain boycotts without any evaluation of their anticompetitive effects

Parallel Exclusion

Scholars and courts have long debated whether and when parallel pricing – adoption of the same price by every firm in a market – should be considered a violation of antitrust law. But there has been a comparative neglect of the importance of parallel exclusion – conduct, engaged in by multiple firms, that blocks or slows would-be market entrants. Parallel exclusion merits greater attention, for it can be far more harmful than parallel price elevation. Setting a high price leaves the field open for new entrants and may even attract them. In contrast, parallel action that excludes new entrants both facilitates price elevation and can slow innovation. Reduced innovation has greater long-term significance for the economy. Moreover, parallel exclusion regimes may be more stable than parallel price-elevation regimes. A basic game-theoretic analysis reveals that the factors that leave price elevation vulnerable to breakdown do not apply as strongly to parallel exclusion. Indeed, in some instances, maintaining an exclusion scheme is a dominant strategy for each of the excluders. In such cases, the likelihood of collapse is even lower, yielding a potentially indefinite system of parallel exclusion. This Article proposes the recognition of parallel exclusion as a form of monopolization – subject to the strict limits already present in case law, including monopoly power, anticompetitive effect, and an absence of sufficient procompetitive justification. It also explains why parallel exclusion is a proper concern for merger policy, and why it is bad policy to automatically condemn certain boycotts without any evaluation of their anticompetitive effects

Nascent Competitors

A nascent competitor is a firm whose prospective innovation represents a serious threat to an incumbent. Protecting such competition is a critical mission for antitrust law, given the outsized role of unproven outsiders as innovators and the uniquely potent threat they often pose to powerful entrenched firms. In this Article, we identify nascent competition as a distinct analytical category and outline a program of antitrust enforcement to protect it. We make the case for enforcement even where the ultimate competitive significance of the target is uncertain, and explain why a contrary view is mistaken as a matter of policy and precedent. Depending on the facts, troubling conduct can be scrutinized under ordinary merger law or as unlawful maintenance of monopoly, an approach that has several advantages. In distinguishing harmful from harmless acquisitions, certain evidence takes on heightened importance. Evidence of an acquirer’s anticompetitive plan, as revealed through internal communications or subsequent conduct, is particularly probative. After-the-fact scrutiny is sometimes necessary as new evidence comes to light. Finally, our suggested approach poses little risk of dampening desirable investment in startups, as it is confined to acquisitions by those firms most threatened by nascent rivals

Nascent Competitors

A nascent competitor is a firm whose prospective innovation represents a serious threat to an incumbent. Protecting such competition is a critical mission for antitrust law, given the outsized role of unproven outsiders as innovators and the uniquely potent threat they often pose to powerful entrenched firms In this Article, we identify nascent competition as a distinct analytical category and outline a program of antitrust enforcement to protect it. We make the case for enforcement even where the ultimate competitive significance of the target is uncertain, and explain why a contrary view is mistaken as a matter of policy and precedent. Depending on the facts, troubling conduct can be scrutinized under ordinary merger law or as unlawful maintenance of monopoly, an approach that has several advantages. In distinguishing harmful from harmless acquisitions, certain evidence takes on heightened importance. Evidence of an acquirer’s anticompetitive plan, as revealed through internal communications or subsequent conduct, is particularly probative. After-the-fact scrutiny is sometimes necessary as new evidence comes to light. Finally, our suggested approach poses little risk of dampening desirable investment in startups, as it is confined to acquisitions by those firms most threatened by nascent rivals

Spaceboard II Panels: Preliminary Evaluation of Mechanical Properties

This preliminary evaluation of the properties of Spaceboard II (SBII) was undertaken to establish the potential of a pulp-molded product in structural-use applications and to develop a basis upon which to optimize the Spaceboard pulp molding process. Various tests were implemented to characterize significant engineering properties, including static concentrated load, panel bending, panel shear, bearing strength, and coupon tension and compression strength. Although these tests were preliminary in nature, they were nonetheless adequate to show that SBII panels perform quite satisfactorily under "dry" conditions, relative to the current performance requirements established for structural-use panels. Our tests on SBII demonstrated that with proper formation and densification, a three-dimensional pulp molding process such as Spaceboard provides the opportunity to create structural products from fiber and to obtain the performance required of conventional products

The spread of a finite group

A group G is said to be 3/2-generated if every nontrivial element belongs to a generating pair. It is easy to see that if G has this property, then every proper quotient of G is cyclic. In this paper we prove that the converse is true for finite groups, which settles a conjecture of Breuer, Guralnick and Kantor from 2008. In fact, we prove a much stronger result, which solves a problem posed by Brenner and Wiegold in 1975. Namely, if G is a finite group and every proper quotient of G is cyclic, then for any pair of nontrivial elements x1,x2∈G, there exists y∈G such that G=⟨x1,y⟩=⟨x2,y⟩. In other words, s(G)⩾2, where s(G) is the spread of G. Moreover, if u(G) denotes the more restrictive uniform spread of G, then we can completely characterise the finite groups G with u(G)=0 and u(G)=1. To prove these results, we first establish a reduction to almost simple groups. For simple groups, the result was proved by Guralnick and Kantor in 2000 using probabilistic methods, and since then the almost simple groups have been the subject of several papers. By combining our reduction theorem and this earlier work, it remains to handle the groups with socle an exceptional group of Lie type, and this is the case we treat in this paper.PostprintPeer reviewe

Crab pulsar giant pulses: Simultaneous radio and GRO observations

Observations are reported of the Crab pulsar made at radio frequencies concurrent with Oriented Scintillation Spectrometer Experiment (OSSE) observations from 15 to 27 May 1991. Using the 43 m telescope at Green Bank at 0.8 and 1.4 GHz, samples were made continuously for 10 hrs/day at intervals of 100 to 300 microsecs. The analysis of the radio data includes calculation of histograms of pulse intensities, absolute timing to about 20 microsec precision, and characterization of intensity variations on time scales from the 33 ms spin period to days. The most detailed analysis is presented made of giant pulses. The ultimate goal is to bin the radio data into giant and nongiant pulses and to form average waveforms of OSSE data for the corresponding pulse periods. A test is done to see whether the violet radio fluctuations (which are not seen in other radio pulsars to the same degree) are correlated with low energy gamma rays, yielding constraints on the radio coherence mechanism and the steadiness of the electron-positron outflow in the magnetosphere. Timing analysis of the radio data provides a well defined ephemeris over the specified range of epochs. The gamma ray pulse phase was predicted with an error of less than 70 microsecs

Re-engineering the Multimission Command System at the Jet Propulsion Laboratory

The Operations Engineering Lab (OEL) at JPL has developed the multimission command system as part of JPL's Advanced Multimission Operations System. The command system provides an advanced multimission environment for secure, concurrent commanding of multiple spacecraft. The command functions include real-time command generation, command translation and radiation, status reporting, some remote control of Deep Space Network antenna functions, and command file management. The mission-independent architecture has allowed easy adaptation to new flight projects and the system currently supports all JPL planetary missions (Voyager, Galileo, Magellan, Ulysses, Mars Pathfinder, and CASSINI). This paper will discuss the design and implementation of the command software, especially trade-offs and lessons learned from practical operational use. The lessons learned have resulted in a re-engineering of the command system, especially in its user interface and new automation capabilities. The redesign has allowed streamlining of command operations with significant improvements in productivity and ease of use. In addition, the new system has provided a command capability that works equally well for real-time operations and within a spacecraft testbed. This paper will also discuss new development work including a multimission command database toolkit, a universal command translator for sequencing and real-time commands, and incorporation of telecommand capabilities for new missions

Investigating Overdensities around z > 6 Galaxies through ALMA Observations of [C II]

We present a search for companion [C II] emitters to known luminous sources at 6 < z < 6.5 in deep, archival ALMA observations. The observations are deep enough to detect sources with L_([CII])∼10⁸ at z ∼6. We identify three new robust line detections from a blind search of five deep fields centered on ultraluminous infrared galaxies and QSOs. We calculate the volume density of companions and find a relative overdensity of 6⁺⁴₋₃ and 86⁺⁶⁰₋₃₇ when comparing to current observational constraints and theoretical predictions, respectively. These results suggest that the central sources may be highly biased tracers of mass in the early universe. We find these companion lines to have comparable properties to other known galaxies at the same epoch. All companions lie less than 650 km s⁻¹ and between 25 and 60 kpc (projected) from their central source. To place these discoveries in context, we employ a mock galaxy catalog to estimate the luminosity function for [C II] during reionization and compare to our observations. The simulations support this result by showing a similar level of elevated counts found around such luminous [C II] sources