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Hipparcos observations of double stars, mainly A and F primaries, aremodelled in order to check the statistics of double-star solutions inthe Hipparcos Catalogue and to set quantitative limits on binarydistributions. The number of companions per primary is estimated to 0.25+/-0.05 for semi-major axes from 1 to 10 AU, and to 0.43 +/-0.20 for therange 10--100 AU. The total multiplicity found is betw

The motivation for using a zero-dispersion monochromator as a band-pass filter with a Fourier transform spectrometer is discussed, and the design of such an instrument is presented. Benefits in performance over commercial band-pass filters are demonstrated. In addition the advantages of using the second optical output of the spectrometer are discussed, particularly with respect to absorption spect

cut-open-cut February 2025, March 2024 Using transversal video as a tool for exploring transmodal remediationDuring this spring clarinettist Robert Ek will explore embodied music cognition from two directions with composer Kent Olofsson and choreographer Lidia Wos in several labs at IAC. Embodied music cognition describes how our body is a natural mediator of musical events, meaning that we simply

https://www.iac.lu.se/research/visiting-researchers/robert-ek - 2026-05-19

Event generators play a crucial role in the exploration of LHC physics. This presentation summarizes news and plans for the three general-purpose pp generators HERWIG, PYTHIA and SHERPA, as well as briefer notes on a few other generators. Common themes, such as the matching and merging between matrix elements and parton showers, are highlighted. Other topics include a historical introduction, from

After a brief discussion of the statistics available to the four LEP experiments at the time of writing and an overview of B-event characteristics, the authors consider in particular the theory, practice and potential pitfalls of neural networks, a new approach to B tagging which attracted a great deal of interest. They then consider some of the QCD aspects of heavy flavour physics. Finally there

Rescattering effects in the 3π system in the A1 region are studied with a method, which fulfils unitarity and has the proper analytic structure. Fairly small effects are obtained which confirm the result found in amplitude analyses, neglecting rescattering corrections, that the phases of the JP = 1+ amplitudes vary only very little over the A1 region. Similar results hold for the Q enhancement.

This talk describes the reasons why $\eta$ and $\eta^\prime$ decays are an interesting topic of study for both theory and experiment. The main part discusses the results of the recent calculation of $\eta\to3\pi$ at two-loop order in ChPT. Some puzzling aspects of the results compared to earlier dispersive calculations are highlighted. I also like to remind the reader of the use of $\eta$ and $\et

Världen är föränderlig. För att kunna överleva måste allt liv kunna anpassa sig till rådande förhållanden. För cellen, livets minsta enhet, sker detta bland annat genom reglering av produktionstakten av proteiner, vilka är de molekyler som utför de flesta grundläggande funktioner. En speciell klass av proteiner utgörs av så kallade transkriptionsfaktorer. Dessa slår av eller på en gens produktion Living organisms can be viewed as complex biological machines. In order to function, they must regulate their internal mechanism to do the right thing, at the right time, and in the right amount. Part of this regulation is encoded in gene regulatory networks. These are built up of genes which produce special proteins (transcription factors, tf) that regulate other tf-producing genes. Thus a networ

We discuss some of the effects of twisted boundary conditions in finite volume using continuum SU(3) Chiral Perturbation Theory. We point out how broken cubic symmetry affects the definitions of quantities such as form-factors. Using the π+ as an example, we give one loop results for the mass, decay constants and electromagnetic form-factor and illustrate how the relevant Ward identities are satis

An overview is given of Chiral Perturbation Theory and various applications to eta decays. In particular. the main decay eta --> 3pi is discussed at the one-loop level, and estimates of the higher order corrections are given. The importance of p(6) and higher order effects in double Dalitz and eta --> pi(0)gammagamma decays is pointed out. In all these cases the need for new experimental results i

We compare different procedures for combining fixed-order tree-level matrix-element generators with parton showers. We use the case of W-production at the Tevatron and the LHC to compare different implementations of the so-called CKKW and MLM schemes using different matrix-element generators and different parton cascades. We find that although similar results are obtained in all cases, there are i

We present a method to combine the all-order treatment of the High Energy Jets exclusive partonic Monte Carlo (HEJ) with the parton shower of Pythia8, while retaining the logarithmic accuracy of both. This procedure enables the generation of fully realistic and hadronised events with HEJ. Furthermore, the combination of the two allorder treatments leads to improvements in the quality of the descri

A framework of operator product expansion (OPE) allows us to study high-energy behaviour of Green functions. A calculation of such Green functions within chiral perturbation theory (PT) or resonance chiral theory (RT) and subsequent matching of the result to the OPE enables us to determine constraints for unknown parameters of the effective theories. We present such procedure for Green functions i

The present status of Chiral Perturbation Theory (ChPT) in the strong mesonic sector is discussed. A very short introduction to ChPT is followed by an overview of existing two-loop calculations and the determination of the Low-Energy-Constants (LECs). I discuss the case of $\eta\to\pi\pi\pi$ decays in somewhat more detail and finish by mentioning some recent work on partially quenched ChPT and on

This essay is a survey about how important laws regarding women, has lead forward to present day's legislation regarding women battering in Sweden. We have chosen to concentrate on the battered woman's situation. The laws has through centuries given the man a right to beat his wife. Has the way of looking at women's situation in society changed the laws regarding women battering? Has t

Det är i princip omöjligt att överskatta vikten av begreppet symmetri för modern fysik. Redan när Maxwell på 1800-talet förenade elektricitet och magnetism till en enda kraft fanns en underlig egenskap i hans teori. Hans fysikaliska system kännetecknas av potentialer, som är relaterade till de elektriska och magnetiska fälten. Det visade sig att om man förändrar dessa potentialer enligt specifikaWe have studied left-right-symmetric (LR) model building in two specific instances: the Minimal Left-Right-Symmetric Model (MLRM), with gauge group SU(3)_C × SU(2)_L × SU(2)_R × U(1)_{B-L} and parity as the LR symmetry; and a non-supersymmetric, trinified theory, with gauge structure SU(3)_L × SU(3)_R × SU(3)_C × Z_3 and an additional, novel, SU(3) family symmetry. For the MLRM, we have rederive