The Effective Potential, the Renormalisation Group and Vacuum Stability

We review the calculation of the the effective potential with particular emphasis on cases when the tree potential or the renormalisation-group-improved, radiatively corrected potential exhibits non-convex behaviour. We illustrate this in a simple Yukawa model which exhibits a novel kind of dimensional transmutation. We also review briefly earlier work on the Standard Model. We conclude that, despite some recent claims to the contrary, it can be possible to infer reliably that the tree vacuum does not represent the true ground state of the theory.Comment: 23 pages; 5 figures; v2 includes minor changes in text and additional reference

Choice of geographic unit influences socioeconomic inequalities in breast cancer survival

Socioeconomic differences in age-standardised crude survival for women diagnosed with breast cancer during 1991–1999 in England were influenced by the population of the geographic area used to assign the deprivation index, but not by the choice of index

Mitigating agency risk between investors and ventures’ managers

The general management literature has long focused on the agency risks involved in the relationship between general managers and shareholders. Shareholders can deploy contractual and non-contractual mechanisms to reduce these inefficiencies. This study examines - based on a broad international sample of investment contracts - how the use of contractual and non-contractual mechanisms is related to the degree of risks associated with the venture’s development stage as well as how these practices differ across countries. Hypotheses are tested using a proprietary dataset of 265 hand-collected investment contracts associated with ventures in the U.S., Israel and nine European countries. Findings suggest that the use of mitigating contractual and non-contractual mechanisms is related to the degree of agency risks, and that these practices vary across countries. This study draws implications for how investors can best deploy their capital in different institutional settings whilst nurturing their relationships with managers and entrepreneurs

The Highly Unusual Chemical Composition of the Hercules Dwarf Spheroidal Galaxy

We report on the abundance analysis of two red giants in the faint Hercules dwarf spheroidal (dSph) galaxy. These stars show a remarkable deficiency in the neutron-capture elements, while the hydrostatic alpha-elements (O, Mg) are strongly enhanced. Our data indicate [Ba/Fe] and [Mg/Fe] abundance ratios of <-2 dex and ~+0.8 dex, respectively, with essentially no detection of other n-capture elements. In contrast to the only other dSph star with similar abundance patterns, Dra 119, which has a very low metallicity at [Fe/H]=-2.95 dex, our objects, at [Fe/H]~-2.0 dex, are only moderately metal poor. The measured ratio of hydrostatic/explosive alpha-elements indicates that high-mass (~35 M_sun) Type II supernovae progenitors are the main, if not only, contributors to the enrichment of this galaxy. This suggests that star formation and chemical enrichment in the ultrafaint dSphs proceeds stochastically and inhomogeneously on small scales, or that the IMF was strongly skewed to high mass stars. The neutron capture deficiencies and the [Co/Fe] and [Cr/Fe] abundance ratios in our stars are similar to those in the extremely low metallicity Galactic halo. This suggests that either our stars are composed mainly of the ejecta from the first, massive, population III stars (but at moderately high [Fe/H]), or that SN ejecta in the Hercules galaxy were diluted with ~30 times less hydrogen than typical for extreme metal-poor stars.Comment: 5 pages, 3 figures, accepted by Astrophysical Journal Letter

Pedestrian Approach to the Two-Channel Kondo Model

We reformulate the two-channel Kondo model to explicitly remove the unscattered charge degrees of freedom. This procedure permits us to move the non-Fermi liquid fixed point to infinite coupling where we can apply a perturbative strong-coupling expansion. The fixed point Hamiltonian involves a three-body Majorana zero mode whose scattering effects give rise to marginal self-energies. The compactified model is the N=3 member of a family of "O(N)" Kondo models that can be solved by semiclassical methods in the large $N$ limit. For odd $N$, {\em fermionic} "Kink" fluctuations about the $N=\infty$ mean-field theory generate a fermionic $N$-body bound-state which asymptotically decouples at low energies. For N=3, our semi-classical methods fully recover the non-Fermi liquid physics of the original two channel model. Using the same methods, we find that the corresponding O(3) Kondo lattice model develops a spin-gap and a gapless band of coherently propagating three-body bound-states. Its strong-coupling limit offers a rather interesting realization of marginal Fermi liquid behavior.Comment: 17 pages, Revtex 3.0. Replaced with fully compiled postscript file

Post-Newtonian corrections to the motion of spinning bodies in NRGR

In this paper we include spin and multipole moment effects in the formalism used to describe the motion of extended objects recently introduced in hep-th/0409156. A suitable description for spinning bodies is developed and spin-orbit, spin-spin and quadrupole-spin Hamiltonians are found at leading order. The existence of tidal, as well as self induced finite size effects is shown, and the contribution to the Hamiltonian is calculated in the latter. It is shown that tidal deformations start formally at O(v^6) and O(v^10) for maximally rotating general and compact objects respectively, whereas self induced effects can show up at leading order. Agreement is found for the cases where the results are known.Comment: 18 pages, 9 figures. Typos corrected, to appear in Physical Review

The Robustness of Quintessence

Recent observations seem to suggest that our Universe is accelerating implying that it is dominated by a fluid whose equation of state is negative. Quintessence is a possible explanation. In particular, the concept of tracking solutions permits to adress the fine-tuning and coincidence problems. We study this proposal in the simplest case of an inverse power potential and investigate its robustness to corrections. We show that quintessence is not affected by the one-loop quantum corrections. In the supersymmetric case where the quintessential potential is motivated by non-perturbative effects in gauge theories, we consider the curvature effects and the K\"ahler corrections. We find that the curvature effects are negligible while the K\"ahler corrections modify the early evolution of the quintessence field. Finally we study the supergravity corrections and show that they must be taken into account as $Q\approx m_{\rm Pl}$ at small red-shifts. We discuss simple supergravity models exhibiting the quintessential behaviour. In particular, we propose a model where the scalar potential is given by $V(Q)=\frac{\Lambda^{4+\alpha }}{Q^{\alpha}}e^{\frac{\kappa}{2}Q^2}$. We argue that the fine-tuning problem can be overcome if $\alpha \ge 11$. This model leads to $\omega_Q\approx -0.82$ for $\Omega_{\rm m}\approx 0.3$ which is in good agreement with the presently available data.Comment: 16 pages, 7 figure

Development of a lightweight camera for high altitude platform systems

We describe the development of a lightweight, high-resolution surveillance camera for deployment on high altitude platform systems. The instrument is designed to operate at an altitude of ∼20 km and has an expected ground resolution of better than 120 mm with an appropriate sensor. While designed specifically for imaging at visible wavelengths, it is shown that the design is capable of diffraction-limited imaging at NIR and SWIR wavelengths up to 2.5 μm. We have combined a range of materials from aluminum and titanium alloys through to carbon fiber reinforced plastic to produce an instrument with structural components that match the thermal expansion of the optical glasses used. The use of these materials has resulted in an instrument that weighs <2 kg, including a sensor package, and is designed to weigh <3 kg once integrated with an enclosure and actuated gimbal. The successful testing of two prototype systems is described, including several design outcomes from the program intended for implementation in advance of flight trials