Microscopic 8-quark study of the antikaon nucleon nucleon systems

We study the possibility to bind eight quarks in a molecular hadronic system composed of two nucleons and an antikaon, with the quantum numbers of a hexaquark flavour, in particular with strangeness -1, isospin 1/2, parity -, baryonic number 2 and two possible spins, 0 or 1. These exotic hadrons are motivated by the deuteron, a proton-neutron boundstate, and by the model of the Lambda(1405) as an antikaon proton boundstate. We discuss the possible production of this hadron in the experiments which are presently investigating hot topics like the Theta+ pentaquark or the K- deeply bound in nuclei. The K- N interactions and the coupling to other channels are computed microscopically from a confining and chiral invariant quark model resulting in local plus separable Gaussian potentials. The N N interactions used here are the state of the art Nijmegen potentials. The binding energy and the decay rate of the K- N and K- N N systems are computed with configuration space variational methods. The only systems that bind with our microscopic interaction are the K- N in the I=0 channel and the K- N N in the S=0 channel.Comment: 5 pages, 5 figures (1 new and 2 updated), more detailed study of binding with a small parameter increase, and an algebraic correction, submitted to Physical Review

Helices at Interfaces

Helically coiled filaments are a frequent motif in nature. In situations commonly encountered in experiments coiled helices are squeezed flat onto two dimensional surfaces. Under such 2-D confinement helices form "squeelices" - peculiar squeezed conformations often resembling looped waves, spirals or circles. Using theory and Monte-Carlo simulations we illuminate here the mechanics and the unusual statistical mechanics of confined helices and show that their fluctuations can be understood in terms of moving and interacting discrete particle-like entities - the "twist-kinks". We show that confined filaments can thermally switch between discrete topological twist quantized states, with some of the states exhibiting dramatically enhanced circularization probability while others displaying surprising hyperflexibility

Origin of the anomalous long lifetime of 14C

We report the microscopic origins of the anomalously suppressed beta decay of 14C to 14N using the ab initio no-core shell model (NCSM) with the Hamiltonian from chiral effective field theory (EFT) including three-nucleon force (3NF) terms. The 3NF induces unexpectedly large cancellations within the p-shell between contributions to beta decay, which reduce the traditionally large contributions from the NN interactions by an order of magnitude, leading to the long lifetime of 14C.Comment: 4 pages, 2 figures and 2 table

Designing-in of Quality Through Axiomatic Design

Decisions made during the design stage of product & process development profoundly affect product quality and process productivity. To aid in design decision making, a theoretical framework is advanced: the axiomatic approach to design. Axiomatic design consists of: 1) domains in the design world, 2) mapping between these domains, 3) characterization of a design by a vector in each domain, 4) decomposition of the characteristic vectors into hierarchies through a process of zigzagging between the domains, and 5) the design axioms, viz, Independence & Information Axioms. Statistical process control (SE) and other methodologies to improve quality are valid only when they are consistent with the Independence & Information Axioms. This paper presents several criteria that govern the design & manufacture of quality products, To be able to control the quality of products, a design must satisfy the Independence Axiom. Based on this axiom and some theorems, several design criteria are derived & discussed. These criteria provide the bounds for the validity of some of the SPC techniques being used. When there is more than one acceptable design of a product or process, the Information Axiom must be used to select the best design(s)

On the Maximal Excess Charge of the Chandrasekhar-Coulomb Hamiltonian in Two Dimensions

We show that for the straightforward quantized relativistic Coulomb Hamiltonian of a two-dimensional atom -- or the corresponding magnetic quantum dot -- the maximal number of electrons does not exceed twice the nuclear charge. It result is then generalized to the presence of external magnetic fields and atomic Hamiltonians. This is based on the positivity of |\bx| T(\bp) + T(\bp) |\bx| which -- in two dimensions -- is false for the non-relativistic case T(\bp) = \bp^2, but is proven in this paper for T(\bp) = |\bp|, i.e., the ultra-relativistic kinetic energy

Possible methods for the determination of the PP-parity of the Θ+\Theta^+-pentaquark in NN-collisions

We present two possibilities to determine the P-parity of the pentaquark $\Theta^+$, in a model independent way, via the measurement of polarization observables in $p+p\to \Theta^+ +\Sigma^+$, or $n+p\to \Theta^+ +\Lambda^0$, in the near threshold region. Besides the measurement of the spin correlation coefficient, $A_{xx}=A_{yy}$, (in collisions of transversally polarized nucleons), the coefficient $D_{xx}$ of polarization transfer from the initial proton to the final $\Sigma^+(\Lambda^0)$ hyperon is also unambiguously related to the $\Theta^+$ parity.Comment: 7 pages, 1 figur

Free Energy Approach to the Formation of an Icosahedral Structure during the Freezing of Gold Nanoclusters

The freezing of metal nanoclusters such as gold, silver, and copper exhibits a novel structural evolution. The formation of the icosahedral (Ih) structure is dominant despite its energetic metastability. This important phenomenon, hitherto not understood, is studied by calculating free energies of gold nanoclusters. The structural transition barriers have been determined by using the umbrella sampling technique combined with molecular dynamics simulations. Our calculations show that the formation of Ih gold nanoclusters is attributed to the lower free energy barrier from the liquid to the Ih phases compared to the barrier from the liquid to the face-centered-cubic crystal phases