Computational aerothermodynamics

Computational aerothermodynamics (CAT) has in the past contributed to the understanding of real-gas flows encountered by hypervelocity reentry vehicles. With advances in computational fluid dynamics, in the modeling of high temperature phenomena, and in computer capability, CAT is an enabling technology for the design of many future space vehicles. An overview of the current capabilities of CAT is provided by describing available methods and their applications. Technical challenges that need to be met are discussed

A Study of Degenerate Four-quark states in SU(2) Lattice Monte Carlo

The energies of four-quark states are calculated for geometries in which the quarks are situated on the corners of a series of tetrahedra and also for geometries that correspond to gradually distorting these tetrahedra into a plane. The interest in tetrahedra arises because they are composed of {\bf three } degenerate partitions of the four quarks into two two-quark colour singlets. This is an extension of earlier work showing that geometries with {\bf two} degenerate partitions (e.g.\ squares) experience a large binding energy. It is now found that even larger binding energies do not result, but that for the tetrahedra the ground and first excited states become degenerate in energy. The calculation is carried out using SU(2) for static quarks in the quenched approximation with $\beta=2.4$ on a $16^3\times 32$ lattice. The results are analysed using the correlation matrix between different euclidean times and the implications of these results are discussed for a model based on two-quark potentials.Comment: Original Raw PS file replace by a tarred, compressed and uuencoded PS fil

Four-quark flux distribution and binding in lattice SU(2)

The full spatial distribution of the color fields of two and four static quarks is measured in lattice SU(2) field theory at separations up to 1 fm at beta=2.4. The four-quark case is equivalent to a qbar q qbar q system in SU(2) and is relevant to meson-meson interactions. By subtracting two-body flux tubes from the four-quark distribution we isolate the flux contribution connected with the four-body binding energy. This contribution is further studied using a model for the binding energies. Lattice sum rules for two and four quarks are used to verify the results.Comment: 46 pages including 71 eps figures. 3D color figures are available at www.physics.helsinki.fi/~ppennane/pics

Leiter on the Legal Realists

In this essay reviewing Brian Leiter’s recent book Naturalizing Jurisprudence, I focus on two positions that distinguish Leiter’s reading of the American legal realists from those offered in the past. The first is his claim that the realists thought the law is only locally indeterminate – primarily in cases that are appealed. The second is his claim that they did not offer a prediction theory of law, but were instead committed to a standard positivist theory. Leiter’s reading is vulnerable, because he fails to discuss in detail those passages from the realists that inspired past interpretations. My goal is to see how Leiter’s reading fares when these passages are considered. I argue that Leiter is right that the realists’ indeterminacy thesis has only a local scope. Those passages that appear to claim that the law is globally indeterminate actually address three other topics: judicial supremacy, judges’ roles as finders of fact, and the moral obligation to adjudicate as the law commands. With respect to the prediction theory, however, I conclude that Leiter’s position cannot be defended. Indeed the realists offered two ‘prediction’ theories of law. According to the first, which is best described as a decision theory, the law concerning an event is whatever concrete judgment a court will issue when the event is litigated. According to the second, the law is reduced, not to concrete judgments, but to regularities of judicial (and other official) behavior in a jurisdiction. I end this essay with the suggestion that the realists’ advocacy of the second prediction theory indirectly vindicates Leiter’s reading of the realists as prescient jurisprudential naturalists

Does Dworkin Commit Dworkin’s Fallacy?: A Reply to Justice in Robes

In an article entitled ‘Dworkin’s Fallacy, Or What the Philosophy of Language Can’t Teach Us about the Law’, I argued that in Law’s Empire Ronald Dworkin misderived his interpretive theory of law from an implicit interpretive theory of meaning, thereby committing ‘Dworkin’s fallacy’. In his recent book, Justice in Robes, Dworkin denies that he committed the fallacy. As evidence he points to the fact that he considered three theories of law—‘conventionalism’, ‘pragmatism’ and ‘law as integrity’—in Law’s Empire. Only the last of these is interpretive, but each, he argues, is compatible with his interpretive theory of meaning, which he describes as the view that ‘the doctrinal concept of law is an interpretive concept’. In this Reply, I argue that Dworkin’s argument that he does not commit Dworkin’s fallacy is itself an example of the fallacy and that Dworkin’s fallacy pervades Justice in Robes just as much as it did Law’s Empire