Quantum field tomography

We introduce the concept of quantum field tomography, the efficient and reliable reconstruction of unknown quantum fields based on data of correlation functions. At the basis of the analysis is the concept of continuous matrix product states, a complete set of variational states grasping states in quantum field theory. We innovate a practical method, making use of and developing tools in estimation theory used in the context of compressed sensing such as Prony methods and matrix pencils, allowing us to faithfully reconstruct quantum field states based on low-order correlation functions. In the absence of a phase reference, we highlight how specific higher order correlation functions can still be predicted. We exemplify the functioning of the approach by reconstructing randomised continuous matrix product states from their correlation data and study the robustness of the reconstruction for different noise models. We also apply the method to data generated by simulations based on continuous matrix product states and using the time-dependent variational principle. The presented approach is expected to open up a new window into experimentally studying continuous quantum systems, such as encountered in experiments with ultra-cold atoms on top of atom chips. By virtue of the analogy with the input-output formalism in quantum optics, it also allows for studying open quantum systems.Comment: 31 pages, 5 figures, minor change

Magnetism in layered Ruthenates

In this thesis, the magnetism of the layered Ruthenates has been studied by means of different neutron scattering techniques. Magnetic correlations in the single-layer Ruthenates of the series Ca2-xSrxRuO4 have been investigated as function of Sr-concentration (x=0.2 and 0.62), temperature and magnetic field. These inelastic neutron scattering studies demonstrate the coexistence of ferromagnetic paramagnon scattering with antiferromagnetic fluctuations at incommensurate wave vectors. The temperature dependence of the amplitudes and energies of both types of excitations indicate the proximity to magnetic instabilities; their competition seems to determine the complex behavior of these materials. In Ca1.8Sr0.2RuO4, which shows a metamagnetic transition, the ferromagnetic fluctuations are strongly suppressed at low temperature, but appear at higher temperature or application of a magnetic field. In the high-field phase of Ca1.8Sr0.2RuO4 above the metamagnetic transition, a ferromagnetic magnon dominates the excitation spectrum. Polarized neutron scattering revealed the existence of a very broad signal around the zone centre, in addition to the well-known incommensurate excitations at Q=(0.3,0.3,0) in the unconventional superconductor Sr2RuO4. With this additional contribution, it is possible to set up a general model for the Q-dependent magnetic susceptibility, which is well consistent with the results of other measurement methods that do not resolve the Q-dependence. Upon doping with Ti, the incommensurate fluctuations are enhanced, in particular near the critical concentration for the onset of magnetic order, but no divergence down to very low temperature is observed. In the bilayer Ti-doped Sr3Ru2O7, the existence of magnetic order with a propagation vector of about (1/4 ,1/4 ,0) has been discovered and characterized in detail. Above and below TN, excitations at this wave vector and another one, related to Sr3Ru2O7, have been observed. Furthermore, in a polarized neutron diffraction study, the spin density distribution of Ca3Ru2O7 has been determined

Standard map in magnetized relativistic systems: fixed points and regular acceleration

We investigate the concept of a standard map for the interaction of relativistic particles and electrostatic waves of arbitrary amplitudes, under the action of external magnetic fields. The map is adequate for physical settings where waves and particles interact impulsively, and allows for a series of analytical result to be exactly obtained. Unlike the traditional form of the standard map, the present map is nonlinear in the wave amplitude and displays a series of peculiar properties. Among these properties we discuss the relation involving fixed points of the maps and accelerator regimes.Comment: Work to appear in Phys. Rev. E. 2 figure

Improvement in soybean sprouts production with ultrasound power.

The present work aimed the application of different ultrasound powers (10, 50 and 90W) to evaluate the germination and characteristics of soybean sprouts fromsoybeans of cultivar BRS 216 and 3 lines (A, B and C). In the germination test,the line A showed the highest percentage of germination (96% for 90W).The cultivar BRS 216 and line A present lower values of weight and higher yield of sprouts. The viable sprouts that presented the highest weight (for each 50g of soybean) were: line A followed by BRS 216, line C and B, with statistical differences (p<0.05) between them. For each 50g of soybean of cultivar BRS 216 and Lines A, B and C the production of viable sprouts was 231.47; 237.87; 170.74 and 199.94g, respectively, for 90W. In relation to the length of the sprouts using the power of 10W the line C presented a longer length. The line A using 90W showed better color characteristics. The highest protein value was found in cultivar BRS 216, for all applied potencies. With this work it can be concluded that the line A would be the most suitable for sprout production regardless of the ultrasound power applie

Universality of dispersive spin-resonance mode in superconducting BaFe2As2

Spin fluctuations in superconducting BaFe2(As1-xPx)2 (x=0.34, Tc = 29.5 K) are studied using inelastic neutron scattering. Well-defined commensurate magnetic signals are observed at ({\pi},0), which is consistent with the nesting vector of the Fermi surface. Antiferromagnetic (AFM) spin fluctuations in the normal state exhibit a three-dimensional character reminiscent of the AFM order in nondoped BaFe2As2. A clear spin gap is observed in the superconducting phase forming a peak whose energy is significantly dispersed along the c-axis. The bandwidth of dispersion becomes larger with approaching the AFM ordered phase universally in all superconducting BaFe2As2, indicating that the dispersive feature is attributed to three-dimensional AFM correlations. The results suggest a strong relationship between the magnetism and superconductivity.Comment: 5 pages, 5 figure

Do people remember what is prototypical?:The role of accent-religion intersectionality for individual and category memory

Evidence suggests that accents can be typically more powerful in activating ethnicity categorization than appearance. Concurrently, some social categories, such as ethnicity, can be linked with other categories, such as religion. We investigate how people categorize those who belong to a (mis)matching pair of categories? In the present study we investigated Germans’ categorization of women either wearing a headscarf (Muslim religious symbol), or not, and speaking either standard German or German with an Arabic accent. The “Who Said What?” paradigm and multinomial modelling yielded that category memory, indicative of subtyping, was best for non-prototypical targets (i.e., headscarf and standard German accent, no headscarf and Arabic accent). In contrast, ingroup targets (no headscarf and standard German accent) were individually remembered better than all other targets, whereas non-prototypical targets (no-headscarf and Arabic accent) were not remembered individually at all. These findings are discussed in terms of intersectionality and category prototypicality

Ingroup projection as a challenge of diversity: consensus about and complexity of superordinate categories

As is often done, we could begin such a chapter in a volume on intergroup conflict with a dire description of the state of human society and the continuing menace of social discrimination, prejudice, injustice, and ethnic violence. However, a children's book by the Austrian writer Edith Schreiber-Wicke (1990), whose title may be translated as “When the crows were still colorful,” provides a fable that is more fun, yet insightful. It describes the story of the crows when they still came in all sorts of colors and patterns – orange with blue stripes, green with yellow spots, and so on – until one day a snowman asked the fateful (and probably spiteful) question of what a real, true crow looked like. Now the yellow-with-blue-spotted crows declared yellow with blue spots was the true color of crows, but the lilac crows argued the ur-crow was lilac colored, and all the other crows also claimed their colors were the real ones. There was arguing and quarreling; the crows began to fly with like-colored others only. The fighting ended only when one day a black rain turned all animals black. Afterward, only the crows stayed black and no longer had a reason to argue. The moral of the story? Obviously: ingroup projection is a challenge of diversity! And if we do not want to buy social harmony with dull sameness, we had better think of a more creative way to appreciate and enjoy differences. Ingroup projection is the perception or claim that one's own group is more prototypical for a higher-order superordinate identity, hence more normative and positive, than a relevant comparison outgroup is, or more prototypical at least than the outgroup thinks the ingroup is. In the present chapter, we briefly outline the ingroup projection model (IPM; Mummendey & Wenzel, 1999; Wenzel, Mummendey, & Waldzus, 2007), discuss its key concepts and relevant recent findings, and essentially argue for two ways in which we need to construe our superordinate identities to reduce tension between diverse and divergent groups included in them: We need to advance consensus about the superordinate identity in question, and about the complexity of its representation.info:eu-repo/semantics/acceptedVersio