Massless Monopoles and Multipronged Strings

We investigate the role of massless magnetic monopoles in the N=4 supersymmetric Yang-Mills Higgs theories. They can appear naturally in the 1/4-BPS dyonic configurations associated with multi-pronged string configurations. Massless magnetic monopoles can carry nonabelian electric charge when their associated gauge symmetry is unbroken. Surprisingly, massless monopoles can also appear even when the gauge symmetry is broken to abelian subgroups.Comment: 10 pages, LaTex file, more comments added. (To appear in Phys. Lett. B

Luther v. Borden: A Taney Court Mystery Solved

It has not been generally remarked that Chief Justice Taney wrote surprisingly few of the Taney Court’s major opinions—those cases that tend to be anthologized and remembered by generalists. Those major cases which Taney did write are consistently about slavery (or states’ rights or state powers, which in Taney’s mind may have amounted to the same thing). There is a notable exception: Luther v. Borden—a case about the Guarantee Clause. This raises a question. Setting aside his opinions on slavery or states’ rights, what could have moved the author of Dred Scott, by consensus the worst Supreme Court opinion in history, to choose Luther v. Borden as one of the few remembered major opinions he did write? To begin to unravel this little mystery of history, a glimpse into the character and judgment of Roger Brooke Taney is offered, with an amusing parallel drawn between the respective nominations to the Supreme Court of Taney and Robert Bork. Luther is reconsidered in light of the Transcripts of Record, and with an unembarrassed presentism rather than historicism. In view of Chief Justice Warren’s thinking in Powell v. McCormack, much of Chief Justice Taney’s reasoning in Luther is shown not only to be evasive, illogical and unconvincing, but also intellectually dishonest, if he is to be credited with the understandings of law and its processes reasonably attributable to a former Attorney General of the United States. Even more disturbingly, Luther v. Borden can plausibly be read as having a darker side than is conventionally understood, with an impact of surprising magnitude and hurtfulness, placing it well within the ambitions of the author of Dred Scott

Entropy Production during Asymptotically Safe Inflation

The Asymptotic Safety scenario predicts that the deep ultraviolet of Quantum Einstein Gravity is governed by a nontrivial renormalization group fixed point. Analyzing its implications for cosmology using renormalization group improved Einstein equations we find that it can give rise to a phase of inflationary expansion in the early Universe. Inflation is a pure quantum effect here and requires no inflaton field. It is driven by the cosmological constant and ends automatically when the renormalization group evolution has reduced the vacuum energy to the level of the matter energy density. The quantum gravity effects also provide a natural mechanism for the generation of entropy. It could easily account for the entire entropy of the present Universe in the massless sector.Comment: 17 pages, 4 figures, Invited contribution to the special issue of Entropy on "Entropy in Quantum Gravity

Pions in Large-NN Quantum Chromodynamics

An effective field theory of quarks, gluons, and pions, with the number $N$ of colors treated as large, is proposed as a basis for calculations of hadronic phenomena at moderate energies. The qualitative consequences of the large $N$ limit are similar though not identical to those in pure quantum chromodynamics, but because constituent quark masses appear in the effective Lagrangian, the `t Hooft coupling in the effective theory need not be strong at moderate energies. To leading order in $1/N$ the effective theory is renormalizable, with only a finite number of terms in the Lagrangian.Comment: Version to be published in Phys. Rev. Letters. Two figures added, text and abstract revised and shortened. Clearer statement of aims of work. 9 page