An Infrared Renormalization Group Limit Cycle in QCD

Small increases in the up and down quark masses of QCD would tune the theory to the critical renormalization group trajectory for an infrared limit cycle in the three-nucleon system. At critical values of the quark masses, the deuteron binding energy goes to zero and the triton has infinitely many excited states with an accumulation point at the 3-nucleon threshold. The ratio of the binding energies of successive states approaches a universal constant that is close to 515. The proximity of physical QCD to the critical trajectory for this limit cycle explains the success of an effective field theory of nucleons with contact interactions only in describing the low-energy 3-nucleon system.Comment: 4 pages, revtex4, 2 ps figure

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

Site-dependent acellularisation effects explain altered tissue mechanics: ultrastructural insights

Acellular scaffolds are used for the surgical repair of soft tissue injury forming a biological basis for cell remodelling. Previously tissue-dependent effects sodium-dodecyl-sulphate (SDS) have been determined on the extracellular matrix (ECM) of different tissue types. This short report aims at extending these findings onto a tissue-layer level with focus on the ECM. Porcine ureters, oesophagi and skin underwent acellularisation using SDS, whereas control samples remained in a native condition. The samples were investigated histologically and ultrastructurally electron microscopy. Dense collagen bundles were seen in all native samples throughout the layers, and moderate to strong decreases in collagen density in the acellular state, accompanied by clumping. Collagen bundles were altered differently. Transition from straightened into coiled alignment was observed in the ureters’ intima and all oesophageal layers, the opposite was observed in the ureters’ media and adventitia. Skin samples appeared discontinuously following acellularisation, with collagens curling in the subcutis and dermis and disruptions in the subepidermis. Collagen fibre integrity appeared unchanged. SDS-related alterations include tissue- and site-dependent alterations of the collagen bundles. These insights into the ECM provide further explanation of acellularisation-induced change in mechanical properties, resulting in increased stiffness in ureters, and stiffness in skin

Family Supportive Supervision Around the Globe

Family-supportive supervision (FSS) refers to the degree to which employees perceive their immediate supervisors as exhibiting attitudes and behaviors that are supportive of their family role demands (Hammer, Kossek, Zimmerman, & Daniels, 2007; Kossek, Pichler, Bodner & Hammer, 2011: Thomas & Ganster, 1995). A growing body of research suggests that leaders\u27 and supervisors\u27 social support of employees\u27 needs to jointly carry out work and family demands is important for general health and job attitudes, such as satisfaction, work-family conflict, commitment, and intention to turn over (Hammer, Kossek, Anger, Bodner, & Zimmerman, 2009; Kossek et al., 2011). Thus, employee perceptions of FSS are critical to individual well-being and productivity (Hammer, Kossek, Yragui, Bodner, & Hansen, 2009). [excerpt

Enhanced Dimer Relaxation in an Atomic/Molecular BEC

We derive a universal formula for the rate constant \beta for relaxation of a shallow dimer into deeply-bound diatomic molecules in the case of atoms with a large scattering length a. We show that \beta is determined by a and by two 3-body parameters that also determine the binding energies and widths of Efimov states. The rate constant \beta scales like \hbar a/m near the resonance, but the coefficient is a periodic function of ln(a) that may have resonant enhancement at values of a that differ by multiples of 22.7.Comment: 5 pages, revtex4, 2 PS figures, title changed, final versio

Simulating the impact of the Smith Cloud

We investigate the future evolution of the Smith Cloud by performing hydrodynamical simulations of the cloud impact onto the gaseous Milky Way Galactic disk. We assume a local origin for the cloud and thus do not include a dark matter component to stabilize it. Our main focus is the cloud's influence on the local and global star formation rate (SFR) of the Galaxy and whether or not it leads to an observable event in the far future. Our model assumes two extremes for the mass of the Smith Cloud, an upper mass limit of 10$^7$ M$_{\odot}$ and a lower mass limit of 10$^6$ M$_{\odot}$, compared to the observational value of a few 10$^6$ M$_{\odot}$. In addition, we also make the conservative assumption that the entirety of the cloud mass of the extended Smith Cloud is concentrated within the tip of the cloud. We find that the impact of the low-mass cloud produces no noticeable change in neither the global SFR nor the local SFR at the cloud impact site within the galactic disk. For the high-mass cloud we find a short-term (roughly 5 Myr) increase of the global SFR of up to 1 M$_{\odot}$ yr$^{-1}$, which nearly doubles the normal Milky Way SFR. This highly localized starburst should be observable.Comment: 14 pages, 5 figure

Universal Properties of Two-Dimensional Boson Droplets

We consider a system of N nonrelativistic bosons in two dimensions, interacting weakly via a short-range attractive potential. We show that for N large, but below some critical value, the properties of the N-boson bound state are universal. In particular, the ratio of the binding energies of (N+1)- and N-boson systems, B_{N+1}/B_N, approaches a finite limit, approximately 8.567, at large N. We also confirm previous results that the three-body system has exactly two bound states. We find for the ground state B_3^(0) = 16.522688(1) B_2 and for the excited state B_3^(1) = 1.2704091(1) B_2.Comment: 4 pages, 2 figures, final versio

Resonant Dimer Relaxation in Cold Atoms with a Large Scattering Length

Efimov physics refers to universal phenomena associated with a discrete scaling symmetry in the 3-body problem with a large scattering length. The first experimental evidence for Efimov physics was the recent observation of a resonant peak in the 3-body recombination rate for 133Cs atoms with large negative scattering length. There can also be resonant peaks in the atom-dimer relaxation rate for large positive scattering length. We calculate the atom-dimer relaxation rate as a function of temperature and show how measurements of the relaxation rate can be used to determine accurately the parameters that govern Efimov physics.Comment: 4 pages, 2 eps figures, normalization error in figures corrected, equations unchange