Search results for "sironta"

Scattering and point spectra for elliptic systems in domains with cylindrical ends

2004

Viktor Kalvinen tieteellisen laskennan alaan kuuluva väitöskirjatutkimus käsittelee elliptisiä reuna-arvotehtäviä sylinteripäisissä alueissa. Sylinteripäinen alue mallitetaan työssä eräänlaisena aaltoputkena, johon tulee ja josta lähtee erilaisia aaltoja. Näiden aaltojen amplitudi voi kasvaa eksponentiaalisesti kohti ääretöntä. Kalvine on kehittänyt tutkimuksessaan ns. augmentoidun sirontamatriisin, joka perinteisiin sirontamatriiseihin verrattuna kykenee käsittelemään myös amplitudiltaan eksponentiaalisesti muuttuvia aaltoja. Työssä esitellään myös numeerinen menetelmä kyseisen sirontamatriisin laskemiseksi. In the thesis we consider dissipative elliptic boundary value problems in domains …

Refined instability estimates for some inverse problems

2022

Many inverse problems are known to be ill-posed. The ill-posedness can be manifested by an instability estimate of exponential type, first derived by Mandache [29]. In this work, based on Mandache's idea, we refine the instability estimates for two inverse problems, including the inverse inclusion problem and the inverse scattering problem. Our aim is to derive explicitly the dependence of the instability estimates on key parameters. The first result of this work is to show how the instability depends on the depth of the hidden inclusion and the conductivity of the background medium. This work can be regarded as a counterpart of the depth-dependent and conductivity-dependent stability estim…

Asymptotic and numerical studies of electron scattering in 2D quantum waveguides of variable cross-section

2012

Next-to-leading order corrections to deep inelastic scattering structure functions at small Bjorken-x

2017

Syvän epäelastisen sironnan kokeellisia tuloksia on kuvattu onnistuneesti pie- nillä Bjorkenin x:n arvoilla käyttämällä sironnan dipolimallia ja johtavan kerta- luvun valokartiohäiriöteoriaa. On tärkeää selvittää, paraneeko teorian kuvaavuus tutkimalla vaikutuksia korkeampien kertalukujen häiriöteoriasta. Mittaustulosten kuvauksen parantamiseksi tässä työssä johdetaan korjauksia johtavan kertaluvun vaikutusalaan ja rakennefunktioihin häiriöteorian toisessa ker- taluvussa. Tämän toteuttamiseksi esitellään tarvittavassa määrin valokartiokvant- tikenttäteoria, pienen Bjorken-x sironnan dipolimalli ja häiriöteoriaa. Johdettu toi- sen kertaluvun vaikutusalala sisältää pehmeän divergenssin proses…

Diffractive deep inelastic scattering at NLO in the dipole picture: The qq¯g contribution

2022

We calculate the contribution from the qq¯g state production to the diffractive cross sections in deep inelastic scattering at high energy. The obtained cross section is finite by itself and a part of the full next-to-leading order result for the diffractive structure functions. We perform the calculation in exact kinematics in the eikonal limit, and show that the previously known high-Q2 and large MX2 results for the structure functions can be extracted from our results in the appropriate limits. We furthermore discuss the steps required to obtain the full next-to-leading order results for the structure functions.

Investigation of the elastic and inelastic scattering of 4He from 11B in the energy range 29-50.5 MeV

2018

We have measured the angular distributions for the elastic and inelastic scattering of 4He from 11B in the isochronous cyclotron U-150 M INP RK. The extracted α-particles beam has been accelerated to energy 29 MeV and then directed to 11B target. The experimental results were analyzed within the framework of both the optical model using different complex potential and the double folding potential obtained with different density-dependent NN interactions which give the corresponding values of the nuclear incompressibility K in the Hartree-Fock calculation of nuclear matter. peerReviewed

Theoretical predictions of wimp-nucleus and neutrino-nucleus scattering in context of dark matter direct detection

2018

The nature of dark matter is at present an open question. Assuming the main component of dark matter consists of weakly interacting massive particles (WIMPs), directly detecting such particle via a scattering process with an atomic nucleus would be a strong probe into properties of dark matter. So far direct detection experiments have not provided a conclusive signal of dark matter. Traditionally the experiments aim to detect a coherent, spin- independent, elastic scattering signal which is enhanced by the square of the nuclear mass number. If the coherent channel is for some reason suppressed for WIMP-nucleus interactions, then spin-dependent interactions become important. In this thesis w…

Interaction between surface plasmon polaritons and molecules in strong coupling limit

2016

Miniaturization of optical elements and their integration to electronic circuits is limited by diffraction limit. It was realized that light being coupled to surface plasmons (SP) can overcome this limit. Employing also optically active molecules in combination with SPs can drive optical circuits to nm-scale and add functionalities. For efficient performance of plasmonic elements involving fluorescent dye molecules investigation of physics behind their interaction is of high priority. In this thesis interaction between surface plasmon polaritons (SPPs) and different dye molecules has been studied, especially within strong coupling limit, which brings in totally new physical properties in th…