Infrared cutoff dependence of the critical flavor number in three-dimensional QED

We solve, analytically and numerically, a gap equation in parity invariant QED_3 in the presence of an infrared cutoff \mu and derive an expression for the critical fermion number N_c as a function of \mu. We argue that this dependence of N_c on the infrared scale might solve the discrepancy between continuum Schwinger-Dyson equations studies and lattice simulations of QED_3.Comment: 5 pages, 1 figure (revtex4), final versio

Renormalization Flow of Bound States

A renormalization group flow equation with a scale-dependent transformation of field variables gives a unified description of fundamental and composite degrees of freedom. In the context of the effective average action, we study the renormalization flow of scalar bound states which are formed out of fundamental fermions. We use the gauged Nambu--Jona-Lasinio model at weak gauge coupling as an example. Thereby, the notions of bound state or fundamental particle become scale dependent, being classified by the fixed-point structure of the flow of effective couplings.Comment: 25 pages, 3 figures, v2: minor corrections, version to appear in PR

Towards a renormalizable standard model without fundamental Higgs scalar

We investigate the possibility of constructing a renormalizable standard model with purely fermionic matter content. The Higgs scalar is replaced by point-like fermionic self-interactions with couplings growing large at the Fermi scale. An analysis of the UV behavior in the point-like approximation reveals a variety of non-Gaussian fixed points for the fermion couplings. If real, such fixed points would imply nonperturbative renormalizability and evade triviality of the Higgs sector. For point-like fermionic self-interactions and weak gauge couplings, one encounters a hierarchy problem similar to the one for a fundamental Higgs scalar.Comment: 18 pages, 4 figure

Complicaties van niet-insuline-afhankelijke diabetes mellitus in de huisartspraktijk

Contains fulltext : mmubn000001_147830664.pdf (publisher's version ) (Open Access)Promotor : C. van Weel115 p

Approach to treatment of dyspepsia in primary care - A randomized trial comparing "Test-and-treat" with prompt endoscopy

Background: The value of the "test-and-treat" strategy in the approach to dyspepsia has been evaluated only in a few secondary care studies. Most patients with dyspepsia, however, are treated by their primary care physician. This study evaluated the test-and-treat strategy in primary care. Methods: Patients consulting their general practitioners for dyspepsia were randomized to either direct open-access endoscopy with Helicobacter pylori testing or a test-and-treat strategy by H pylori serology. In the 12-month follow-up period, any additional treatment or referral for investigations was left at the discretion of the general practitioner. At the end of the study, data were collected concerning the number of endoscopies, changes in symptom severity and quality of life, patient satisfaction, and the use of medical resources. Results: Two hundred seventy patients were enrolled (129 who received endoscopy and 141 in the test-and-treat group). The prevalence of H pylori infection was 38.3% and 37.2% in the test-and-treat and endoscopy groups, respectively. In the test-and-treat group, 46 patients (33%) were referred for endoscopy during follow-up. Improvement in symptom severity, quality of life, and patient satisfaction was comparable in both groups. Patients in the test-and-treat group paid more dyspepsia-related visits to their general practitioner (P=.005). Patients in the endoscopy group were more often prescribed proton pump inhibitors (P=.007), whereas patients in the test-and-treat group were more often prescribed prokinetic drugs (P=.005). Conclusions: The test-and-treat strategy proved to be as effective and safe as prompt endoscopy. Only a minority of patients were referred for endoscopy after the test-and-treat approach