Showing papers by "University of Warsaw published in 1996"

Tolerance approximation spaces

Abstract: We generalize the notion of an approximation space introduced in [8] In tolerance approximation spaces we define the lower and upper set approximations We investigate some attribute reduction problems for tolerance approximation spaces determined by tolerance information systems The tolerance relation defined by the so called uncertainty function or the positive region of a given partition of objects have been chosen as invariants in the attribute reduction process We obtain the solutions of the reduction problems by applying boolean reasoning [1] The solutions are represented by tolerance reducts and relative tolerance reducts

Sobolev Spaces on an Arbitrary Metric Space

Abstract: We define Sobolev space W1,p for 1

Performance of the DELPHI detector

Abstract: DELPHI (DEtector with Lepton, Photon and Hadron Identification) is a detector for e^+e^- physics, designed to provide high granularity over a 4\pi solid angle, allowing an effective particle identification. It has been operating at the LEP (Large Electron-Positron) collider at CERN since 1989. This article reviews its performance.

Direct probing of quantum phase space by photon counting.

Abstract: We propose a very simple experimental setup to measure, via photon counting, the overlap of the Wigner functions characterizing two single mode light beams. We show that this scheme can be applied to determine directly the phase space quasiprobability distribution of the single mode field and in a certain limit the Wigner function can be measured without use of tomographic reconstruction algorithms. The deleterious effects of nonunit photodetector efficiency are analyzed.

From multiplicative unitaries to quantum groups

Abstract: An alternative version of the theory of multiplicative unitaries is presented. Instead of the original regularity condition of Baaj and Skandalis we formulate another condition selecting manageable multiplicative unitaries. The manageability is the property of multiplicative unitaries coming from the quantum group theory. For manageable multiplicative unitaries we reproduce all the essential results of the original paper of Baaj and Skandalis and much more. In particular the existence of the antipode and its polar decomposition is shown.

Power spectrum of primordial inhomogeneity determined from the four year COBE DMR sky maps

Abstract: Fourier analysis and power spectrum estimation of the cosmic microwave background anisotropy on an incompletely sampled sky developed by Gorski has been applied to the 4 yr COBE DMR 31.5, 53, and 90 GHz sky maps. Likelihood analysis using newly constructed Galaxy cuts (extended beyond |b| = 20° to excise the known foreground emission) and simultaneously correcting for the faint high-latitude Galactic foreground emission is conducted on the DMR sky maps pixelized in both ecliptic and Galactic coordinates. The Bayesian power spectrum estimation from the foreground-corrected 4 yr COBE DMR data renders n ~ 1.2 ± 0.3 and Qrms-PS ~ 15.3 -->−2.8+3.7 μK (projections of the two-parameter likelihood). The results are consistent with the Harrison-Zeldovich n = 1 model of amplitude Qrms-PS ~ 18 μK detected with significance exceeding 14 σ (δQ/Q 0.07). (A small power spectrum amplitude drop below the published 2 yr results is predominantly due to the application of the new, extended Galaxy cuts.)

Raman Spectroscopic Studies of Regioregular Poly(3-alkylthiophenes)

Abstract: Raman spectra of neutral and electrochemically doped regioregular poly(3-decylthiophene) were studied using different excitation lines, namely, 457.9, 514.5, 676, and 1064 nm. Contrary to the case of nonregioregular poly(3-decylthiophene) obtained by polymerization with FeCl3, in regioregular polymer the position of the principal band (due to the CαCβ stretchings) is essentially independent of the excitation wavelength, proving its high structural homogeneity and extended conjugation. Raman spectroelectrochemical studies of oxidative doping of regioregular poly(3-decylthiophene) can be clearly correlated with cyclic voltammetry and UV−visible−near-IR spectroelectrochemistry provided that appropriate excitation wavelengths are selected. In particular, the use of the red (676.4 nm) and near-IR (1064 nm) excitation lines enables us to register the doping induced changes in the Raman spectra, whereas the green (514.5 nm) line always reveals the vibrations from the undoped segments of the polymer chain indepen...

Tuning and test of fragmentation models based on identified particles and precision event shape data

Abstract: Event shape and charged particle inclusive distributions are measured using 750000 decays of the Z to hadrons from the DELPHI detector at LEP. These precise data allow a decisive confrontation with models of the hadronization process. Improved tunings of the JETSET, ARIADNE and HERWIG parton shower models and the JETSET matrix element model are obtained by fitting the models to these DELPHI data as well as to identified particle distributions from all LEP experiments. The description of the data distributions by the models is critically reviewed with special importance attributed to identified particles.

Microwave Emission at High Galactic Latitudes in the Four-Year DMR Sky Maps

Abstract: We use the COBE Differential Microwave Radiometers (DMR) 4 yr sky maps to model Galactic microwave emission at high latitudes (|b| > 20°). Cross-correlation of the DMR maps with Galactic template maps detects fluctuations in the high-latitude microwave sky brightness with the angular variation of the DIRBE far-infrared dust maps and a frequency dependence consistent with a superposition of dust and free-free emission. We find no significant correlations between the DMR maps and various synchrotron templates. On the largest angular scales (e.g., quadrupole), Galactic emission is comparable in amplitude to the anisotropy in the cosmic microwave background (CMB). The CMB quadrupole amplitude, after correction for Galactic emission, has amplitude Qrms = 10.7 μK with random uncertainty 3.6 μK and systematic uncertainty 7.1 μK from uncertainty in our knowledge of Galactic microwave emission.

Two-Point Correlations in the COBE DMR Four-Year Anisotropy Maps

Abstract: The two-point temperature correlation function is evaluated from the 4 yr COBE DMR microwave anisotropy maps. We examine the two-point function, which is the Legendre transform of the angular power spectrum, and show that the data are statistically consistent from channel to channel and frequency to frequency. The most likely quadrupole normalization is computed for a scale-invariant power-law spectrum of CMB anisotropy, using a variety of data combinations. For a given data set, the normalization inferred from the two-point data is consistent with that inferred by other methods. The smallest and largest normalizations deduced from any data combination are 16.4 and 19.6 μK, respectively, with a value ~18 μK generally preferred.

Noisy information and computational complexity

Abstract: In this volume, which was originally published in 1996, noisy information is studied in the context of computational complexity; in other words the text deals with the computational complexity of mathematical problems for which information is partial, noisy and priced. The author develops a general theory of computational complexity of continuous problems with noisy information and gives a number of applications; deterministic as well as stochastic noise is considered. He presents optimal algorithms, optimal information, and complexity bounds in different settings: worst case, average case, mixed worst-average and average-worst, and asymptotic. The book integrates the work of researchers in such areas as computational complexity, approximation theory and statistics, and includes many fresh results as well. About two hundred exercises are supplied with a view to increasing the reader's understanding of the subject. The text will be of interest to professional computer scientists, statisticians, applied mathematicians, engineers, control theorists, and economists.

Tests for Non-Gaussian Statistics in the DMR Four-Year Sky Maps

Abstract: We search the high-latitude portion of the COBE Differential Microwave Radiometer (DMR) 4 yr sky maps for evidence of a non-Gaussian temperature distribution in the cosmic microwave background. The genus, three-point correlation function, and two-point correlation function of temperature maxima and minima are all in excellent agreement with the hypothesis that the CMB anisotropy on angular scales of 7? or larger represents a random-phase Gaussian field. A likelihood comparison of the DMR sky maps to a set of random-phase non-Gaussian toy models selects the exact Gaussian model as most likely. Monte Carlo simulations show that the two-point correlation of the peaks and valleys in the maps provides the greatest discrimination among the class of models tested.

In Situ FT-IR/ATR Spectroelectrochemistry of Prussian Blue in the Solid State

Abstract: Interfacial oxidation and reduction of Prussian Blue (PB), KFeIII[FeII(CN)6]·nH2O (n ≈ 10), powder were probed in situ with Fourier transform infrared attenuated total reflection (FT-IR/ATR) spectroscopy. The combination of electrochemistry in the absence of liquid electrolyte with internal reflectance FT-IR spectroscopy was accomplished using a simple two-electrode sandwich-type cell in which a crystalline germanium served both as a working electrode and an infrared transparent element. Application of sufficiently large potential differences to sandwich electrodes led to oxidation and reduction of PB at opposing interfaces. The spectra, which were monitored by difference, clearly show changes in the cyanide stretching frequency range upon oxidation and reduction.

Ferromagnetic superexchange in Cr-based diluted magnetic semiconductors.

Abstract: A theory of superexchange in Cr-based ${\mathit{A}}_{\mathrm{II}}$${\mathit{B}}_{\mathrm{VI}}$ diluted magnetic semiconductors (DMS's) is presented. The spin interaction between ${\mathrm{Cr}}^{2+}$ ions, calculated numerically for zinc chalcogenides, exhibits properties unique in DMS's, it is ferromagnetic, and depends on the relative orientations of the ionic Jahn-Teller distortions. We explain the origin of this unusual behavior and predict a ferromagnetic character of the superexchange in other Cr-based ${\mathit{A}}_{\mathrm{II}}$${\mathit{B}}_{\mathrm{VI}}$ DMS's. \textcopyright{} 1996 The American Physical Society.

Two-and three-body decay modes of SUSY Higgs particles

Abstract: We summarize the dominant decay modes of the neutral and charged Higgs bosons in the Minimal Supersymmetric extension of the Standard Model. While two-body decays are in general dominating, the branching ratios for three-body decays of the heavy scalar, pseudoscalar and charged Higgs bosons can be large below the thresholds if top quarks, W/Z bosons or heavy scalar bosons are involved. Analytical expressions have been derived for the partial decay widths and the physical implications of these decay modes are discussed.

Efficient algorithms for Lempel-Ziv encoding

Abstract: We consider several basic problems for texts and show that if the input texts are given by their Lempel-Ziv codes then the problems can be solved deterministically in polynomial time in the case when the original (uncompressed) texts are of exponential size. The growing importance of massively stored information requires new approaches to algorithms for compressed texts without decompressing. Denote by LZ(ω) the version of a string ω produced by Lempel-Ziv encoding algorithm. For given compressed strings LZ(T), LZ(P) we give the first known deterministic polynomial time algorithms to compute compressed representations of the set of all occurrences of the patternP in T, all periods of T, all palindromes of T, and all squares of T. Then we consider several classical language recognition problems:

Modeling Social Change with Cellular Automata

Abstract: In this paper we will first discuss computer simulations of social processes as models of qualitative understanding. In the second part of the paper we will present the cellular automata model of dynamic social impact (Nowak et al. 1990) and its applications in the areas of the formation of public opinion and social change as an example of a model of qualitative understanding.

On the Origin of the Cooperativity of Protein Folding: Implications From Model Simulations

Abstract: There is considerable experimental evidence that the cooperativity of protein folding resides in the transition from the molten globule to the native state. The objective of this study is to examine whether simplified models can reproduce this cooperativity and if so, to identify its origin. In particular, the thermodynamics of the conformational transition of a previously designed sequence (A. Kolinski, W. Galazka, and J. Skolnick, J. Chem. Phys. 103: 10286-10297, 1995), which adopts a very stable Greek-key beta-barrel fold has been investigated using the entropy Monte Carlo sampling (ESMC) technique of Hao and Scheraga (M.-H. Hao and H.A. Scheraga, J. Phys. Chem. 98: 9882-9883, 1994). Here, in addition to the original potential, which includes one body and pair interactions between side chains, the force field has been supplemented by two types of multi-body potentials describing side chain interactions. These potentials facilitate the protein-like pattern of side chain packing and consequently increase the cooperativity of the folding process. Those models that include an explicit cooperative side chain packing term exhibit a well-defined all-or-none transition from a denatured, random coil state to a high-density, well-defined, nativelike low-energy state. By contrast, models lacking such a term exhibit a conformational transition that is essentially continuous. Finally, an examination of the conformations at the free-energy barrier between the native and denatured states reveals that they contain a substantial amount of native-state secondary structure, about 50% of the native contacts, and have an average root mean square radius of gyration that is about 15% larger than native.

On GaN Crystallization by Ammonothermal Method

Abstract: GaN crystals are grown using ammonothermal method at pressures below 5 kbar and temperatures below 550°C. In this method, GaN is synthesised from high purity metallic gallium. The main role in the low temperature GaN crystallization is played by the chemically active and dense ammonia and dissolved mineralizer. Morphology of the obtained crystals as well as solubility experiments prove that gallium nitride is dissolved and crystallised from solution. Physical properties of GaN crystals obtained using ammonothermal method depend on the growth conditions and the type of mineralizer. All GaN samples reveal very intensive photoluminescence, also at room temperature. The spectra of crystals grown with lithium compound mineralizer are shifted towards higher energies in comparison to crystals grown with potassium based mineralizer. At helium temperatures, phosphorescence is also observed. PACS numbers: 81.10.Dn

On the classification of quantum Poincare groups

Abstract: Using the general theory of (10), quantum Poincare groups (with- out dilatations) are described and investigated. The description con- tains a set of numerical parameters which satisfy certain polynomial equations. For most cases we solve them and give the classification of quantum Poincare groups. Each of them corresponds to exactly one quantum Minkowski space. The Poincare series of these objects are the same as in the classical case. We also classify possible R-matrices for the fundamental representation of the group.

Higher-Order Binding Corrections to the Lamb Shift of 2P States

Abstract: We present an improved calculation of higher-order corrections to the one-loop self-energy of 2P states in hydrogenlike systems with small nuclear charge Z. The method is based on a division of the integration with respect to the photon energy into a high- and a low-energy part. The high-energy part is calculated by an expansion of the electron propagator in powers of the Coulomb field. The low-energy part is simplified by the application of a Foldy-Wouthuysen transformation. This transformation leads to a clear separation of the leading contribution from the relativistic corrections and removes higher-order terms. The method is applied to the 2${\mathit{P}}_{1/2}$ and 2${\mathit{P}}_{3/2}$ states in atomic hydrogen. The results lead to theoretical values for the Lamb shifts and the fine-structure splitting. \textcopyright{} 1996 The American Physical Society.