Dark Energy and the Return of the Phoenix Universe

In cyclic universe models based on a single scalar field (e.g., the radion determining the distance between branes in M-theory), virtually the entire universe makes it through the ekpyrotic smoothing and flattening phase, bounces, and enters a new epoch of expansion and cooling. This stable evolution cannot occur, however, if scale-invariant curvature perturbations are produced by the entropic mechanism because it requires two scalar fields (e.g., the radion and the Calabi-Yau dilaton) evolving along an unstable classical trajectory. In fact, we show here that an overwhelming fraction of the universe fails to make it through the ekpyrotic phase; nevertheless, a sufficient volume survives and cycling continues forever provided the dark energy phase of the cycle lasts long enough, of order a trillion years. Two consequences are a new role for dark energy and a global structure of the universe radically different from that of eternal inflation.Comment: 5 pages, 3 figure

Dark Energy, Inflation and Extra Dimensions

We consider how accelerated expansion, whether due to inflation or dark energy, imposes strong constraints on fundamental theories obtained by compactification from higher dimensions. For theories that obey the null energy condition (NEC), we find that inflationary cosmology is impossible for a wide range of compactifications; and a dark energy phase consistent with observations is only possible if both Newton's gravitational constant and the dark energy equation-of-state vary with time. If the theory violates the NEC, inflation and dark energy are only possible if the NEC-violating elements are inhomogeneously distributed in thecompact dimensions and vary with time in precise synchrony with the matter and energy density in the non-compact dimensions. Although our proofs are derived assuming general relativity applies in both four and higher dimensions and certain forms of metrics, we argue that similar constraints must apply for more general compactifications.Comment: 26 pages, 1 figure. v2: reference added, typos correcte

Determining Which Human Rights Claims Touch and Concern the United States: Justice Kennedy\u27s Filartiga

If statutes were zombies, the Alien Tort Statute of 1789 (ATS) would lead the undead who walk among us. By one conventional narrative, the statute arose from the misty eighteenth-century murk, then lay moribund for nearly two centuries until 1980, when the Second Circuit breathed a strange new life into it with Filartiga v. Pena-Irala. That decision then remained a monstrous curiosity--generative more academic conferences than cases and more awards of tenure than damages--until 1984, when the Court of Appeals for the District of Columbia Circuit decided Tel-Oren v. Libyan Arab Republic. The three-way split among the panel in Tel-Oren suggested that there was no consensus that Filartiga had been rightly decided, and the death watch began in earnest, even as the years passed and jurisdiction was sustained in numerous cases that fit the Filartiga model. This issue of the Notre Dame Law Review, in assessing the impact of Kiobel v. Royal Dutch Petroluem, marks the thirtieth anniversary of the statute\u27s first premature obituary

The Role of International Law As a Canon of Domestic Statutory Construction

From the beginning of our constitutional life, the Supreme Court has articulated principles that structure the juridical relationship between international law and domestic law. These principles purportedly offer rules of decision for resolving in domestic courts the potential in-consistencies between external and internal sources of law, and they do so with the surface simplicity of axioms. Treaties, for example, cannot trump constitutional norms.\u27 Customary international law can provide a rule of decision at least in the absence of controlling legislative or executive acts. In the case of an irreconcilable conflict between a treaty and a statute, the latter-in-time prevails. When Congress incorporates conventional or customary norms into a statute, those norms become directly enforceable and in the absence of any other applicable principle, United States statutes should be read where fairly possible so as not to violate international law. These principles have been criticized variously as innocuous, anomalous, and asymmetrical.\u27 But they also reflect the Court\u27s insistence hat domestic and international law be accommodated, not necessarily as equals, but as two legitimate sources of norms binding on the United States and enforceable in its courts. Doctrinal purity may have been sacrificed, but the Court\u27s accommodationist imperative has had the advantage of avoiding both dualist and monist extremes. As a result of the Supreme Court\u27s approach, the debate persists about the proper way to characterize the relationship between international and domestic law in the United States

Angular Inflation from Supergravity

We study supergravity inflationary models where inflation is produced along the angular direction. For this we express the scalar component of a chiral superfield in terms of the radial and the angular components. We then express the supergravity potential in a form particularly simple for calculations involving polynomial expressions for the superpotential and Kahler potential. We show for a simple Polonyi model the angular direction may give rise to a stage of inflation when the radial field is fixed to its minimum. We obtain analytical expressions for all the relevant inflationary quantities and discuss the possibility of supersymmetry breaking in the radial direction while inflating by the angular component.Comment: 7 pages, one figure. Final version. Title changed, two figures droppe

Cosmological Imprint of an Energy Component with General Equation of State

We examine the possibility that a significant component of the energy density of the universe has an equation-of-state different from that of matter, radiation or cosmological constant ($\Lambda$). An example is a cosmic scalar field evolving in a potential, but our treatment is more general. Including this component alters cosmic evolution in a way that fits current observations well. Unlike $\Lambda$, it evolves dynamically and develops fluctuations, leaving a distinctive imprint on the microwave background anisotropy and mass power spectrum.Comment: revised version, with added references, to appear in Phys. Rev. Lett. (4 pages Latex, 2 postscript figures