Kondo resonance narrowing in d- and f-electron systems

By developing a simple scaling theory for the effect of Hund's interactions on the Kondo effect, we show how an exponential narrowing of the Kondo resonance develops in magnetic ions with large Hund's interaction. Our theory predicts an exponential reduction of the Kondo temperature with spin S of the Hund's coupled moment, a little-known effect first observed in d-electron alloys in the 1960's, and more recently encountered in numerical calculations on multi-band Hubbard models with Hund's interactions. We discuss the consequences of Kondo resonance narrowing for the Mott transition in d-band materials, particularly iron pnictides, and the narrow ESR linewidth recently observed in ferromagnetically correlated f-electron materials.Comment: 4 pages, 3 figure

Bounds on the Compactness of Neutron Stars from Brightness Oscillations

The discovery of high-amplitude brightness oscillations at the spin frequency or its first overtone in six neutron stars in low-mass X-ray binaries during type~1 X-ray bursts provides a powerful new way to constrain the compactness of these stars, and hence to constrain the equation of state of the dense matter in all neutron stars. Here we present the results of general relativistic calculations of the maximum fractional rms amplitudes that can be observed during bursts. In particular, we determine the dependence of the amplitude on the compactness of the star, the angular dependence of the emission from the surface, the rotational velocity at the stellar surface, and whether there are one or two emitting poles. We show that if two poles are emitting, as is strongly indicated by independent evidence in 4U 1636-536 and KS 1731-26, the resulting limits on the compactness of the star can be extremely restrictive. We also discuss the expected amplitudes of X-ray color oscillations and the observational signatures necessary to derive convincing constraints on neutron star compactness from the amplitudes of burst oscillations.Comment: 8 pages plus one figure, AASTeX v. 4.0, submitted to The Astrophysical Journal Letter

Globular Clusters and Dwarf Spheroidal Galaxies

Traditionally globular clusters and dwarf spheroidal galaxies have been distinguished by using one or more of the following criteria: (1) mass, (2) luminosity, (3) size, (4) mass-to-light ratio and (5) spread in metallicity. However, a few recently discovered objects show some overlap between the domains in parameter space that are occupied by galaxies and clusters. In the present note it is shown that ellipticity can, in some cases, be used to help distinguish between globular clusters and dwarf spheroidal galaxies.Comment: MNRAS (Letters), in pres

No supercritical supercurvature mode conjecture in one-bubble open inflation

In the path integral approach to false vacuum decay with the effect of gravity, there is an unsolved problem, called the negative mode problem. We show that the appearance of a supercritical supercurvature mode in the one-bubble open inflation scenario is equivalent to the existence of a negative mode around the Euclidean bounce solution. Supercritical supercurvature modes are those whose mode functions diverge exponentially for large spatial radius on the time constant hypersurface of the open universe. Then we propose a conjecture that there should be ``no supercritical supercurvature mode''. For a class of models that contains a wide variety of tunneling potentials, this conjecture is shown to be correct.Comment: 11 pages, 3 postscript figures, tarred, gzipped. submitted to Phys. Rev. D1

A study of the effects of environmental and ablator performance uncertainties on heat shielding requirements for hyperbolic entry vehicles. Volume 2 - Summary of calculations

Calculated ablative quantities for nylon phenolic heat shielding materials of hyperbolic reentry vehicle

Investigation of the influence of a step change in surface roughness on turbulent heat transfer

The use is studied of smooth heat flux gages on the otherwise very rough SSME fuel pump turbine blades. To gain insights into behavior of such installations, fluid mechanics and heat transfer data were collected and are reported for a turbulent boundary layer over a surface with a step change from a rough surface to a smooth surface. The first 0.9 m length of the flat plate test surface was roughened with 1.27 mm hemispheres in a staggered, uniform array spaced 2 base diameters apart. The remaining 1.5 m length was smooth. The effect of the alignment of the smooth surface with respect to the rough surface was also studied by conducting experiments with the smooth surface aligned with the bases or alternatively with the crests of the roughness elements. Stanton number distributions, skin friction distributions, and boundary layer profiles of temperature and velocity are reported and are compared to previous data for both all rough and all smooth wall cases. The experiments show that the step change from rough to smooth has a dramatic effect on the convective heat transfer. It is concluded that use of smooth heat flux gages on otherwise rough surfaces could cause large errors

Paying for Energy Peaks: Learning from Texas\u27 February 2021 Power Crisis

From February 14–19, 2021, winter storm Uri blanketed Texas with extreme cold. Tragically, the severe temperatures overwhelmed the state’s power system. Texas’ power grid ended up more than 20 Gigawatts short of the electricity Texans needed 2 – more power than all of California produces on an average day. Over two-hundred lives were lost3 and an estimated $295 billion in damage resulted.4 Yet many had long regarded Texas’ electric power system, and its regulation, as a model for others. What happened? That question is the focus of this article. This article first provides an overview of the severe power outages in February 2021 and the regulation of Texas’ electric power system, explaining why Texas is on the forefront of challenges that will grow more prominent as the world transitions to cleaner energy. Next, it discusses competing electric power business models and their regulation, including why many had long viewed Texas as a model of wise electricity regulation, and why the problems revealed by winter storm Uri will only grow more pressing for not just Texas but the entire world as it transitions to more reliance on electricity and a power grid supported by natural gas and renewables. It concludes by discussing Texas’ path forward and the broader lessons of this crisis for business lawyers and others. The tremendous economic losses of this episode attest to the importance of business lawyers having a basic understanding of their clients’ energy dependencies, the risks that significant power problems could present to their businesses, and the ability to advise them as they seek to mitigate such vulnerabilitie

Dirty Black Holes and Hairy Black Holes

An approach based on considerations of the non-classical energy momentum tensor outside the event horizon of a black hole provides additional physical insight into the nature of discrete quantum hair on black holes and its effect on black hole temperature. Our analysis both extends previous work based on the Euclidean action techniques, and corrects an omission in that work. We also raise several issues related to the effects of instantons on black hole thermodynamics and the relation between these effects and results in two dimensional quantum field theory.Comment: 13 pages, Latex, submitted to Physical Review Letter

PHOENIX: Public Health and Obesity in England – the New Infrastructure eXamined First interim report: the scoping review

The PHOENIX project aims to examine the impact of structural changes to the health and care system in England on the functioning of the public health system, and on the approaches taken to improving the public’s health. The scoping review has now been completed. During this phase we analysed: Department of Health policy documents (2010-2013), as well as responses to those documents from a range of stakeholders; data from 22 semi-structured interviews with key informants; and the oral and written evidence presented at the House of Commons Communities and Local Government Committee on the role of local authorities in health issues. We also gathered data from local authority (LA) and Health and Wellbeing Board (HWB) websites and other sources to start to develop a picture of how the new structures are developing, and to collate demographic and other data on local authorities. A number of important themes were identified and explored during this phase. In summary, some key points related to three themes - governance, relationships and new ways of working - were: The reforms have had a profound effect on leadership within the public health system. Whilst LAs are now the local leaders for public health, in a more fragmented system, leadership for public health appears to be more dispersed amongst a range of organisations and a range of people within the LA. At national level, the leadership role is complex and not yet developed (from a local perspective). Accountability mechanisms have changed dramatically within public health, and many people still seem to be unclear about them. Some performance management mechanisms have disappeared, and much accountability now appears to rely on transparency and the democratic accountability that this would (theoretically) enable. The extent to which ‘system leaders’ within PHE are able to influence local decisions and performance will depend on the strength of relationships principally between the LA and the local Public Health England centre. These relationships will take time to develop. Many people have faced new ways of working, in new settings, and with new relationships to build. Public health teams in LAs have faced the most profound of these changes, having gone from a position of ‘expert voice’ to a position where they must defend their opinions and activities in the context of competing demands and severely restricted resources. Public health staff may require new skills, and may need to seek new ‘allies’ to thrive in the new environment. HWBs could be crucial in bringing together a fragmented system and dispersed leadership. The next phase of data collection will begin in March with the initiation of case study work. National surveys will be conducted in June/July this year (2014), and at the same time the following year. In this work, we will further explore the following themes: relationships, governance, decision making, new ways of working, and opportunities and difficulties

Instanton-inspired Model of QCD Phase Transition and Bubble Dynamics

We have reinvestigated the collision of gluonic bubbles in a SU(2) model of QCD which was studied by Johnson, Choi and Kisslinger in the context of the instanton-inspired model of QCD phase transition bubbles with plane wave approximation. We discuss treacherous points of the instanton-inspired model that cause the violation of causality due to the presence of imaginary gluon fields. By constructing a new slightly modified Lorentzian model where we have three independent real gluon fields, we reanalyzed the process of bubble collisions. Our numerical results show some indication of forming a bubble wall in colliding region.Comment: 19 pages, 32 figure