Ray helicity: a geometric invariant for multi-dimensional resonant wave conversion

For a multicomponent wave field propagating into a multidimensional conversion region, the rays are shown to be helical, in general. For a ray-based quantity to have a fundamental physical meaning it must be invariant under two groups of transformations: congruence transformations (which shuffle components of the multi-component wave field) and canonical transformations (which act on the ray phase space). It is shown that for conversion between two waves there is a new invariant not previously discussed: the intrinsic helicity of the ray

Verhoging van de pensioenleeftijd dupeert vele mensen

Verhoging van de leeftijd voor AOW en pensioen tot boven 65, ja zelfs tot 70 jaar, wordt de laatste tijd veelvuldig bepleit, zeer recent door de commissie Nijpels “Grijs Werkt”. Want zo stelt men, de levensduur is langer geworden en de ouderen zijn gezonder. Er wordt een beeld opgeroepen over 65 plussers, dat florissant is , met name van de jongsten in die categorie, de mensen tussen 65 en 70 jaar. Nijpels spreekt zoals vele andere voor hem over het Zwitserlevengevoel. Ook wetenschappers laten zich door dit florissante beeld inspireren. Zij adviseren om bij die mensen geld weg te halen of hun arbeidskracht te benutten, met name om de kosten van de vergrijzing te financieren. Niet alleen de commissie Nijpels heeft gepleit om de AOW-leeftijd in stappen omhoog te brengen, maar ook vele anderen. Begin januari stelde een topambtenaar van Economische Zaken hetzelfde voor, evenals de OESO. Al eerder lieten de Raad van Economisch Adviseurs, de econoom Bovenberg in de NRC en Wellink, de president van de Nederlandse Bank zich in deze geest uit . Het lijkt een eenstemmig koor van adviseurs. Men verwijst daarbij naar Duitsland als voorbeeld. In dat land wordt die verhoging geleidelijk ingevoerd, met de kanttekening dat de vergrijzing daar sterker is

Kwaliteitsindicatoren: Grote vraagtekens bij waarnemingsmethoden

Indicatoren voor kwaliteit in de zorg zijn natuurlijk van zeer groot belang. Het blijkt echter geen eenvoudig onderwerp te zijn. Een discussie onlangs in dit tijdschrift over de vraag of de patiënt wel centraal genoeg staat, getuigt daarvan. Er zijn echter veel meer van die geluiden. Een organisatie als Actiz pleit voor de overgang naar een nieuw meetsysteem.  Ook vanuit Vilans worden zorgen geuit. Sommige krantenberichten stellen dat het hele meetsysteem faalt. In dit korte bestek kunnen we slechts een enkel punt aan de orde stellen. En dat betreft de zeer fundamentele vraag: Hoe en door wie wordt er gemeten ofwel waargenomen om de waarde van een indicator te bepalen. Soortgelijke vragen werden reeds een halve eeuw geleden opgeworpen onder andere door de bekende socioloog Blau: ”Three years of participant observation by Cohen complement the earlier data by revealing the full extent to which maintaining a good record had come to displace service to clients as the dominant goal toward which the interviewers were oriented and the scope of the illicit practices to which they resorted in order to manipulate their records”.  Het gaat dus vooral om de betrouwbaarheid van de waarnemingen.Hoe is het daarmee gesteld

Vortices on Hyperbolic Surfaces

It is shown that abelian Higgs vortices on a hyperbolic surface $M$ can be constructed geometrically from holomorphic maps $f:M \to N$, where $N$ is also a hyperbolic surface. The fields depend on $f$ and on the metrics of $M$ and $N$. The vortex centres are the ramification points, where the derivative of $f$ vanishes. The magnitude of the Higgs field measures the extent to which $f$ is locally an isometry. Witten's construction of vortices on the hyperbolic plane is rederived, and new examples of vortices on compact surfaces and on hyperbolic surfaces of revolution are obtained. The interpretation of these solutions as SO(3)-invariant, self-dual SU(2) Yang--Mills fields on $\R^4$ is also given.Comment: Revised version: new section on four-dimensional interpretation of hyperbolic vortices added

A q-analog of the ADHMN construction and axisymmetric multi-instantons

In the preceding paper (Phys. Lett. B463 (1999) 257), the authors presented a q-analog of the ADHMN construction and obtained a family of anti-selfdual configurations with a parameter q for classical SU(2) Yang-Mills theory in four-dimensional Euclidean space. The family of solutions can be seen as a q-analog of the single BPS monopole preserving (anti-)selfduality. Further discussion is made on the relation to axisymmetric ansatz on anti-selfdual equation given by Witten in the late seventies. It is found that the q-exponential functions familiar in q-analysis appear as analytic functions categorizing the anti-selfdual configurations yielded by axisymmetric ansatz.Comment: 11pages, Latex2e, to appear in Journal of Physics A: Mathematical and General as a `Special Issue/Difference Equations

Recognition of cognitive impairment and depressive symptoms in older patients with heart failure

INTRODUCTION: Cognitive impairment and depression in patients with heart failure (HF) are common comorbidities and are associated with increased morbidity, readmissions and mortality. Timely recognition of cognitive impairment and depression is important for providing optimal care. The aim of our study was to determine if these disorders were recognised by clinicians and, secondly, if they were associated with hospital admissions and mortality within 6 months’ follow-up. METHODS: Patients (aged ≥65 years) diagnosed with HF were included from the cardiology outpatient clinic of Gelre Hospitals. Cognitive status was evaluated with the Montreal Cognitive Assessment test (score ≤22). Depressive symptoms were assessed with the Geriatric Depression Scale (score >5). Patient characteristics were collected from electronic patient files. The clinician was blinded to the tests and asked to assess cognitive status and mood. RESULTS: We included 157 patients. Their median age was 79 years (65–92); 98 (62%) were male. The majority had New York Heart Association functional class II. Cognitive impairment was present in 56 (36%) patients. Depressive symptoms were present in 21 (13%) patients. In 27 of 56 patients (48%) cognitive impairment was not recognised by clinicians. Depressive symptoms were not recognised in 11 of 21 patients (52%). During 6 months’ follow-up 24 (15%) patients were readmitted for HF-related reasons and 18 (11%) patients died. There was no difference in readmission and mortality rate between patients with or without cognitive impairment and patients with or without depressive symptoms. CONCLUSION: Cognitive impairment and depressive symptoms were infrequently recognised during outpatient clinic visits

The Nambu sum rule and the relation between the masses of composite Higgs bosons

We review the known results on the bosonic spectrum in various NJL models both in the condensed matter physics and in relativistic quantum field theory including $^3$He-B, $^3$He-A, the thin films of superfluid He-3, and QCD (Hadronic phase and the Color Flavor Locking phase). Next, we calculate bosonic spectrum in the relativistic model of top quark condensation suggested in \cite{Miransky}. In all considered cases the sum rule appears that relates the masses (energy gaps) $M_{boson}$ of the bosonic excitations in each channel with the mass (energy gap) of the condensed fermion $M_f$ as $\sum M_{boson}^2 = 4 M_f^2$. Previously this relation was established by Nambu in \cite{Nambu} for $^3$He-B and for the s - wave superconductor. We generalize this relation to the wider class of models and call it the Nambu sum rule. We discuss the possibility to apply this sum rule to various models of top quark condensation. In some cases this rule allows to calculate the masses of extra Higgs bosons that are the Nambu partners of the 125 GeV Higgs.Comment: Latex, 15 page

Probing for Instanton Quarks with epsilon-Cooling

We use epsilon-cooling, adjusting at will the order a^2 corrections to the lattice action, to study the parameter space of instantons in the background of non-trivial holonomy and to determine the presence and nature of constituents with fractional topological charge at finite and zero temperature for SU(2). As an additional tool, zero temperature configurations were generated from those at finite temperature with well-separated constituents. This is achieved by "adiabatically" adjusting the anisotropic coupling used to implement finite temperature on a symmetric lattice. The action and topological charge density, as well as the Polyakov loop and chiral zero-modes are used to analyse these configurations. We also show how cooling histories themselves can reveal the presence of constituents with fractional topological charge. We comment on the interpretation of recent fermion zero-mode studies for thermalized ensembles at small temperatures.Comment: 26 pages, 14 figures in 33 part