Universal few-body physics in a harmonic trap

Few-body systems with resonant short-range interactions display universal properties that do not depend on the details of their structure or their interactions at short distances. In the three-body system, these properties include the existence of a geometric spectrum of three-body Efimov states and a discrete scaling symmetry. Similar universal properties appear in 4-body and possibly higher-body systems as well. We set up an effective theory for few-body systems in a harmonic trap and study the modification of universal physics for 3- and 4-particle systems in external confinement. In particular, we focus on systems where the Efimov effect can occur and investigate the dependence of the 4-body spectrum on the experimental tuning parameters.Comment: 20 pages, 10 figures, final version, new references adde

Few-body physics in effective field theory

Effective Field Theory (EFT) provides a powerful framework that exploits a separation of scales in physical systems to perform systematically improvable, model-independent calculations. Particularly interesting are few-body systems with short-range interactions and large two-body scattering length. Such systems display remarkable universal features. In systems with more than two particles, a three-body force with limit cycle behavior is required for consistent renormalization already at leading order. We will review this EFT and some of its applications in the physics of cold atoms and nuclear physics. In particular, we will discuss the possibility of an infrared limit cycle in QCD. Recent extensions of the EFT approach to the four-body system and N-boson droplets in two spatial dimensions will also be addressed.Comment: 10 pages, 5 figures, Proceedings of the INT Workshop on "Nuclear Forces and the Quantum Many-Body Problem", Oct. 200

Theoretical Constraints and Systematic Effects in the Determination of the Proton Form Factors

We calculate the two-photon exchange corrections to electron-proton scattering with nucleon and $\Delta$ intermediate states. The results show a dependence on the elastic nucleon and nucleon-$\Delta$-transition form factors used as input which leads to significant changes compared to previous calculations. We discuss the relevance of these corrections and apply them to the most recent and precise data set and world data from electron-proton scattering. Using this, we show how the form factor extraction from these data is influenced by the subsequent inclusion of physical constraints. The determination of the proton charge radius from scattering data is shown to be dominated by the enforcement of a realistic spectral function. Additionally, the third Zemach moment from the resulting form factors is calculated. The obtained radius and Zemach moment are shown to be consistent with Lamb shift measurements in muonic hydrogen.Comment: minor changes, added references, version to appear in PR

How was the Hubble sequence 6 Gyrs ago?

The way galaxies assemble their mass to form the well-defined Hubble sequence is amongst the most debated topic in modern cosmology. One difficulty is to link distant galaxies to those at present epoch. We aim at establishing how were the galaxies of the Hubble sequence, 6 Gyrs ago. We intend to derive a past Hubble sequence that can be causally linked to the present-day one. We selected samples of nearby galaxies from the SDSS and of distant galaxies from the GOODS survey. We verified that each sample is representative of galaxies. We further showed that the observational conditions necessary to retrieve their morphological classification are similar in an unbiased way. Morphological analysis has been done in an identical way for all galaxies in the two samples. We found an absence of number evolution for elliptical and lenticular galaxies, which strikingly contrasts with the strong evolution of spiral and peculiar galaxies. Spiral galaxies were 2.3 times less abundant in the past, that is exactly compensated by the strong decrease by a factor 5 of peculiar galaxies. It strongly suggests that more than half of the present-day spirals had peculiar morphologies, 6 Gyrs ago, and this has to be accounted by any scenario of galactic disk evolution and formation. The past Hubble sequence can be used to test these scenarios as well as to test evolution of fundamental planes for spirals and bulges.Comment: Version accepted by Astronomy and Astrophysics, October 21 2009. Including low resolution images. 11 pages, 8 figure

Bacteriology of cheese V. Defects of blue (Roquefort-Type) cheese

A black discoloration and a musty flavor in blue cheese were attributed to the growth of Hormodendrum olivaceum, particularly in punch holes and cracks in the surface. Gas formation is of relatively little importance in blue cheese, presumably because of the open texture, which permits the gas to escape, and the unfavorable conditions in the cheese for growth of the common gas-forming organisms. Trials with a culture of Aerobacter aerogenes recently isolated from gassy cheddar cheese showed that inoculations (of the milk) which resulted in very gassy cheddar cheese caused no gas holes or only insignificant numbers in blue cheese. A defect of blue cheese in which a portion of the edges became soft appeared to be caused by excessive moisture in the softened parts of the cheese. The defect was readily reproduced by placing cheese near a humidifier where free moisture could strike it. Various conditions encountered in curing rooms favor the accumulation of moisture on the cheese and thus may be involved in the defect