Imprecise measurements in quantum mechanics

In this thesis the structure and properties of imprecise quantum measurements are investigated. The starting point for this investigation is the representation of a quantum observable as a normalized positive operator measure. A general framework to describe measurement inaccuracy is presented. Requirements for accurate measurements are discussed, and the relation of inaccuracy to some optimality criteria is studied. A characterization of covariant observables is given in the case when they are imprecise versions of a sharp observable. Also the properties of such observables are studied. The case of position and momentum observables is studied. All position and momentum observables are characterized, and the joint positionmomentum measurements are discussed.

Spin-offien vaikutus omistaja-arvoon

Perusteluna spin-offien toteuttamisen taustalta löytyy pyrkimys omistaja-arvon kasvattamiseen. Tämän tutkielman tarkoituksena on selvittää spin-offien vaikutusta omistaja-arvoon lyhyellä ja pitkällä aikavälillä. Aluksi tutkielmassa on tehty selkoa ulkomaisista tutkimustuloksista, joissa käsitellään spin-offien vaikutusta omistaja-arvoon. Saatuja tuloksia on verrattu lopuksi kolmeen suomalaiseen spin-offiin. Aikasempien tutkimusten tuloksiksista käy ilmi että spin-offien toteuttamisella on positiivinen vaikutus omistaja-arvoon sekä lyhyellä että pitkällä aikavälillä. Samanlainen positiivinen vaikutus voidaan todeta myös tässä tutkielmassa tutkituissa kolmessa suomalaisessa spin-off-tapauksessa. Omistaja-arvoon vaikuttavina tekijöinä otettiin huomioon yhtiöiden osakekurssien kehitys, jaetut osingot, osakkeiden jakamiset ja mahdolliset pääomanpalautukset. Tutkittavien suomalaisten yhtiöiden omistaja-arvojen kehitystä mitattiin spin-offin ilmoituspäivän läheisyydessä sekä noin yhdestä kolmeen vuotta spin-offin toteutuksen jälkeen. Saatuja tuloksia verrattiin kotimaisilta osakemarkkinoilta saatuihin keskimääräisiin tuottoihin.

Study of spin polarized nuclear matter and finite nuclei with finite range simple effective interaction

The properties of spin polarized pure neutron matter and symmetric nuclear matter are studied using the finite range simple effective interaction, upon its parametrization revisited. Out of the total twelve parameters involved, we now determine ten of them from nuclear matter, against the nine parameters in our earlier calculation, as required in order to have predictions in both spin polarized nuclear matter and finite nuclei in unique manner being free from uncertainty found using the earlier parametrization. The information on the effective mass splitting in polarized neutron matter of the microscopic calculations is used to constrain the one more parameter, that was earlier determined from finite nucleus, and in doing so the quality of the description of finite nuclei is not compromised. The interaction with the new set of parameters is used to study the possibilities of ferromagnetic and antiferromagnetic transitions in completely polarized symmetric nuclear matter. Emphasis is given to analyze the results analytically, as far as possible, to elucidate the role of the interaction parameters involved in the predictions.

Filmes de titânio-silício preparados por "spin" e "dip-coating"

The conditions for the preparation of luminescent materials, consisting of Eu3+ ions entrapped in a titanium matrix, in the forma of a thin film, using the sol-gel process, are described. The films were obtained from sols prepared with TEOS and TEOT, in the presence of acetylacetone as the hidrolysis-retarding agent, using the dip-coating and spin-coating techniques. The influence of these techniques on the films based on titanium and silicon are presented. The Eu3+ was used as a luminescent probe. The films have been characterized by luminescence, reflection and transmittance. The thickness of the films could be related to the preparation procedure. Transparent thin films have been prepared by dip-coating technique.

Non-Markovian Dynamics of the Spin-Boson Model

Avointen kvanttisysteemien teoria tutkii, miten vuorovaikutus laajan ympäristön kanssa muuttaa kvanttisysteemin dynamiikkaa. Kaikki kvanttisysteemit ovat pohjimmiltaan avoimia, joten tällaisten systeemien ymmärtäminen on välttämätöntä kvanttimaailman ymmärtämiseksi. Spin-bosoni -malli kuvaa avointa kaksitasosysteemiä, joka vuorovaikuttaa bosoneista koostuvan ympäristön kanssa. Useat fysikaaliset systeemit käyttäytyvät kaksitasosysteemin tavoin matalissa lämpötiloissa, jonka vuoksi spin-bosoni -mallilla on merkittävä rooli avointen kvanttisysteemien tutkimuksessa. Tutkielman ensimmäinen luku käsittelee yleistä avointen kvanttisysteemien teoriaa ja menetelmiä ei-Markovisen liikeyhtälön johtamiseksi. Ei-Markovinen liikeyhtälö kuvaa ympäristöstä systeemiin takaisin virtaavan informaation vaikutusta systeemin dynamiikkaan. Toisessa luvussa on johdettu spin-bosoni -mallille ei-Markovinen liikeyhtälö ja tarkasteltu spin-systeemin dynamiikkaa joissain erityistapauksissa. Kolmannessa luvussa on esitelty kvanttihyppymenetelmiä avointen systeemien dynamiikan ratkaisemiseksi ja sovellettu ei-Markovisten kvanttihyppyjen teoriaa spinbosoni -mallin tutkimiseksi. Ei-Markovisten kvanttihyppyjen teoriaa käyttämällä voidaan selittää spin-systeemin tiheysmatriisin populaatioissa ja koherensseissa havaittavien ei-Markovisten efektien alkuperä käännettyjen kvanttihyppyjen avulla. Tutkielman viimeisessä osassa esitellään muutamia spin-bosoni -mallin sovellutuksia fysiikan eri alueilta.

Quantum-to-classical crossover in full counting statistics

The reduction of quantum scattering leads to the suppression of shot noise. In this Letter, we analyze the crossover from the quantum transport regime with universal shot noise to the classical regime where noise vanishes. By making use of the stochastic path integral approach, we find the statistics of transport and the transmission properties of a chaotic cavity as a function of a system parameter controlling the crossover. We identify three different scenarios of the crossover.

Quantum suppression of shot noise in field emitters

We have analyzed the shot noise of electron emission under strong applied electric fields within the Landauer-Bttiker scheme. In contrast to the previous studies of vacuum-tube emitters, we show that in new generation electron emitters, scaled down to the nanometer dimensions, shot noise much smaller than the Schottky noise is observable. Carbon nanotube field emitters are among possible candidates to observe the effect of shot-noise suppression caused by quantum partitioning.

"Spin-Off" acadêmico: criando riquezas a partir de conhecimento e pesquisa

Technology companies created from University research are known as "Academic Spin-Off" (ASO). These innovative companies play an important role for the technological, economical and social development of a country. This work discusses some aspects of ASO companies and their importance to Universities. It is also presented a fictitious history of Prof. João, a chemical researcher who will create an ASO company from his academic research work illustrating the basic steps involved in this process.

Probing quantum gravity using photons from a flare of the active galactic nucleus Markarian 501 observed by the MAGIC telescope

We analyze the timing of photons observed by the MAGIC telescope during a flare of the active galactic nucleus Mkn 501 for a possible correlation with energy, as suggested by some models of quantum gravity (QG), which predict a vacuum refractive index similar or equal to 1 + (E/M-QGn)(n), n = 1, 2. Parametrizing the delay between gamma-rays of different energies as Delta t = +/-tau E-1 or Delta t = +/-tau E-q(2), we find tau(1) = (0.030 +/- 0.012) s/GeV at the 2.5-sigma level, and tau(q) = (3.71 +/- 2.57) x 10(-6) s/GeV2, respectively. We use these results to establish lower limits M-QG1 > 0.21 X 10(18) GeV and M-QG2 > 0.26 x 10(11) GeV at the 95% C.L. Monte Carlo studies confirm the MAGIC sensitivity to propagation effects at these levels. Thermal plasma effects in the source are negligible, but we cannot exclude the importance of some other source effect.

Galvanomagnetic Phenomena in Ga1_xMnxAs

In this work temperature dependences of resistivity in zero field have been obtained for epitaxially grown Ga1_xMnxAs thin films with 6 % and 8 % Mn content in 50 300 K temperature range. Decrease of resistivity has been observed. Negative magnetoresistance has been explained by empirical spin dependent hopping model. Hall effect has been studied and anomalous Hall effect, inherent to ferromagnetic materials, has been observed. Both normal and anomalous Hall coefficients have been calculated from experimental data, as well as hole densities. Activation energy of impurity level has been estimated.

Quantum magnetic deflagration in Mn12 acetate

We report controlled ignition of magnetization reversal avalanches by surface acoustic waves in a single crystal of Mn12 acetate. Our data show that the speed of the avalanche exhibits maxima on the magnetic field at the tunneling resonances of Mn12. Combined with the evidence of magnetic deflagration in Mn12 acetate [Y. Suzuki et al., Phys. Rev. Lett. 95, 147201 (2005)], this suggests a novel physical phenomenon: deflagration assisted by quantum tunneling.

Characterization and quantification of polyradical character

The decomposition of 〈͈Ŝ²〉 into atomic and diatomic contributions (local spin analysis) is used to detect and quantify the polyradical character of molecular systems. A model triradical system is studied in detail, and the local spin analysis is used to distinguish several patterns of local spin distributions and spin-spin interactions that can be found for different electronic states. How close a real molecular system is to an ideal system of k perfectly localized spin centers is utilized to define a measure of its k-radical character. The spin properties and triradical character of the lowest-lying electronic states of a number of all σ, all π, and σ-π organic triradicals are discussed in detail. The local spin contributions exhibit good correlation with experimental triradical stabilization energies

The love marriage : challenging Victorian myths in Anne Brontë’s 'The Tenant of Wildfell Hall'

La tesina analitza com Anne Brontë desafia el mite del casament romàntic a la novel·la The Tenant of Wildfell Hall. Argumento que aquesta crítica es fa mostrant les conseqüències nefastes d’un matrimoni (entre l’Arthur i l’Helen) basat en l’atracció i en la idea que una dona pot salvar un home de mala vida. Malgrat que la novel·la acaba amb un altre casament (entre l’Helen i en Gilbert), si s’analitza en detall es pot veure que presenta elements subversius. Per exemple, la seva unió està basada en igualtat intel·lectual i compatibilitat de caràcters, enlloc d’igualtat econòmica i social

Excitation modes of vortices in submicron magnetic disks

Classical and quantum theory of spin waves in the vortex state of a mesoscopic submicron magnetic disk have been developed with account of the finite mass density of the vortex. Oscillations of the vortex core resemble oscillations of a charged string in a potential well in the presence of the magnetic field. A conventional gyrotropic frequency appears as a gap in the spectrum of spin waves of the vortex. The mass of the vortex has been computed, and the result agrees with experimental findings. The finite vortex mass generates a high-frequency branch of spin waves. The effects of an external magnetic field and dissipation have been addressed.