Results for "Nikolai Lauk"
total 1365took 0.11s
A number-state filter for pulses of lightDec 27 2015Mar 15 2016We present a detailed theoretical analysis of a Fock-state filter based on the photon-number dependent group delay in cavity induced transparency proposed in Phys. Rev. Lett. 105, 013601 (2010). We derive a general expression for the propagation velocity ... More Anomalous Quark Chromomagnetic Moment and Single-Spin AsymmetriesAug 22 2013Dec 26 2013We discuss a nonperturbative mechanism for the single-spin asymmetries (SSA) in the strong interaction. This mechanism is based on the existence of a large anomalous quark chromomagnetic moment (AQCM) induced by the nontrivial topological structure of ... More On sampling theorem with sparse decimated samplesMay 02 2016Nov 20 2016The classical sampling Nyquist-Shannon-Kotelnikov theorem states that a band-limited continuous time function is uniquely defined by infinite two-sided sampling series taken with a sufficient frequency. The paper shows that these band-limited functions ... More QCD in beauty decays: successes and puzzlesJun 08 2004The status of the heavy quark expansion for inclusive B decays is briefly reviewed from the perspective of confronting theory with data and of extracting the heavy quark parameters. A good agreement between properly applied theory and new precision data ... More A "BPS expansion" for B and D mesonsNov 30 2003We analyze consequences of the approximation \mu_\pi^2 -\mu_G^2 << \mu_\pi^2 (a `BPS' limit) for B and D mesons. It is shown that neglecting perturbative effects many power corrections would vanish to all orders in 1/m_Q, in particular those violating ... More On causal band-limited mean square approximationNov 29 2011Aug 10 2012We study causal dynamic approximation of non-bandlimited processes by band-limited processes such that a part of the historical path of the underlying process is approximated in $L_2$-norm by the trace of a band-limited process. This allows to cover the ... More On identity theorem for real functionsNov 04 2009Identity theorem for analytic complex functions says that a function is uniquely defined by its values on a set that contains a density point. The paper presents sufficient conditions for classes of real analytic functions that ensures similar property. ... More On recovering parabolic diffusions from their time-averagesSep 07 2016Mar 27 2017The paper study a possibility to recover a parabolic diffusion from its time-average when the values at the initial time are unknown. This problem can be reformulated as a new boundary value problem where a Cauchy condition is replaced by a prescribed ... More Sub-ideal causal smoothing filters for real sequencesNov 27 2014Jul 04 2015The paper considers causal smoothing of the real sequences, i.e.,discrete time processes in a deterministic setting. A family of causal linear time-invariant filters is suggested. These filters approximate the gain decay for some non-causal smoothing ... More Real and complex k-planes in convex hypersurfacesAug 23 2012It is shown that that the rank of the second fundamental form (resp. the Levi form) of a $\mathcal C^2$-smooth convex hypersurface $M$ in $\Bbb R^{n+1}$ (resp. $\Bbb C^{n+1}$) does not exceed an integer constant $k<n$ near a point $p\in M,$ then through ... More Form-factors of the finite quantum XY-chainDec 22 2009Mar 31 2011Explicit factorized formulas for the matrix elements (form-factors) of the spin operators \sigma^x and \sigma^y between the eigenvectors of the Hamiltonian of the finite quantum periodic XY-chain in a transverse field were derived. The derivation is based ... More The 2D Zakharov-Kuznetsov-Burgers equation on a stripApr 17 2014An initial-boundary value problem for the 2D Zakharov-Kuznetsov-Burgers equation posed on a channel-type strip was considered. The existence and uniqueness results for regular and weak solutions in weighted spaces as well as exponential decay of small ... More Kawahara-Burgers equation on a stripAug 25 2014An initial-boundary value problem for the 2D Kawahara-Burgers equation posed on a channel-type strip was considered. The existence and uniqueness results for regular and weak solutions in weighted spaces as well as exponential decay of small solutions ... More On detecting the dependence of time seriesOct 13 2010This short note suggests a heuristic method for detecting the dependence of random time series that can be used in the case when this dependence is relatively weak and such that the traditional methods are not effective. The method requires to compare ... More On $L_1$-distance between first exit times from two regionsMar 20 2003First exit times from regions and their dependence on variations of boundaries are discussed for diffusion processes. The paper presents an estimate of $L_1$-distance between exit times from two regions via expectations of exit times. Dirac Eigenvalues of higher MultiplicityJan 16 2015Let M be a closed spin manifold of dimension at least three with a fixed topological spin structure. For any Riemannian metric, we can construct the associated Dirac operator. The spectrum of this Dirac operator depends on the metric of course. In 2005, ... More On recovering solutions for SPDEs from their averagesNov 01 2016We study linear stochastic partial differential equations of parabolic type. We consider a new boundary value problem where a Cauchy condition is replaced by a prescribed average of the solution over time and probabilistic space. Well-posedness, existence, ... More On sampling theorem with sparse decimated samplesMay 02 2016Jun 13 2016The classical sampling Nyquist-Shannon-Kotelnikov theorem states that a band-limited continuous time function is uniquely defined by infinite two-sided sampling series taken with a sufficient frequency. The paper shows that these band-limited functions ... More Tests for Comparing Weighted Histograms. Review and ImprovementsJun 21 2016Sep 10 2016Histograms with weighted entries are used to estimate probability density functions. Computer simulation is the main application of this type of histograms. A review on chi-square tests for comparing weighted histograms is presented in this paper. Improvements ... More On one sided band-limitness and extrapolation of sequencesAug 16 2012Aug 29 2016The paper suggests a notion of left band-limitness for one-sided semi-infinite sequences representing traces of two-sided band-limited sequences. A method of detecting these sequences is obtained. For more general one-sided sequences without this feature, ... More Theoretical Aspects of Semileptonic B decaysJun 30 2003Strong interactions are addressed in connection to extracting |V_{cb}| and determining heavy quark parameters. A comprehensive approach allows a robust analysis not relying on a 1/m_c expansion; a percent defendable accuracy in |V_{cb}| becomes realistic. ... More BLM-Resummation and OPE in Heavy Flavor TransitionsOct 20 1996Nov 04 1996An all-order resummation is performed for the effect of the running of the strong coupling in the zero recoil sum rule for the axial current and for the kinetic operator \vec\pi^2. The perturbative corrections to well-defined objects of OPE turn out to ... More Heavy quark expansion in beauty: recent successes and problemsSep 10 2004The status of the QCD-based heavy quark expansion is briefly reviewed. A good agreement between properly applied theory and new precision data is observed. Critical remarks on certain recent claims from HQET are presented. Recent applications to the exclusive ... More A pathwise inference method for the parameters of diffusion termsJun 18 2015Apr 11 2017We consider inference of the parameters of the diffusion term for Cox-Ingersoll-Ross and similar processes with a power type dependence of the diffusion coefficient from the underlying process. We suggest some original pathwise estimates for this coefficient ... More Transmission of a continuous signal via one-bit capacity channelDec 12 2013Jan 21 2015We study the problem of the transmission of currently observed time variable signals via a channel that is capable of sending a single binary signal only for each measurement of the underlying process. For encoding and decoding, we suggest a modification ... More A Proof of Willcocks's ConjectureAug 19 2017Mar 03 2018We give a proof of Willcocks's Conjecture, stating that if $p - q$ and $p + q$ are relatively prime, then there exists a Hamiltonian tour of a $(p, q)$-leaper on a square chessboard of side $2(p + q)$. The conjecture was formulated by T. H. Willcocks ... More The 2D Kawahara equation on half-stripFeb 11 2014We formulate on a half-strip an initial boundary value problem for the two-dmensional Kawahara equation. Existence and uniqueness of a regular solution as well as the exponential decay rate for the elevated norm of small solutions are proven. Stochastic Theory of Foreign Exchange Market DynamicsSep 29 1999A new stochastic theory of a foreign exchange markets dynamics is developed. As a result we have the new probability distribution which well describes statistical and scaling dependencies ''experimentally'' observed in foreign exchange markets in recent ... More On recovering parabolic diffusions from their time-averagesSep 07 2016Oct 11 2016The paper study a possibility to recover a parabolic diffusion from its time-average when the values at the initial time are unknown. This problem can be reformulated as a new boundary value problem where a Cauchy condition is replaced by a prescribed ... More First Order BSPDEs: examples in higher dimensionMar 22 2016May 17 2016The paper studies the First Order BSPDEs (Backward Stochastic Partial Differential Equations)suggested earlier for a case of multidimensional state domain with a boundary. These equations represent analogs of Hamilton-Jacobi-Bellman equations and allow ... More Strong interaction effects in semileptonic B decaysOct 02 2002Strong interaction effects are addressed in connection to extracting |V_{cb}|. A comprehensive approach is described not relying on a 1/m_c expansion; it allows a percent accuracy without ad hoc assumptions about higher-order effects. An alternative to ... More Topics in the Heavy Quark ExpansionOct 30 2000Nov 06 2000Achievements in the heavy quark theory over the last decade are reviewed, with the main emphasis put on dynamical methods which quantify nonperturbative effects via application of the Operator Product Expansion. These include the total weak decay rates ... More Universal estimate of the gradient for parabolic equationsSep 06 2007Apr 29 2008We suggest a modification of the estimate for weighted Sobolev norms of solutions of parabolic equations such that the matrix of the higher order coefficients is included into the weight for the gradient. More precisely, we found the upper limit estimate ... More On recovering missing values for sequences in a pathwise settingApr 18 2016Sep 18 2018The paper suggests a frequency criterion of error-free recoverability of a missing value for sequences, i.e. discrete time processes, in a pathwise setting without probabilistic assumptions. The paper establishes error-free recoverability for classes ... More Machine learning approach to inverse problem and unfolding procedureApr 12 2010May 25 2011A procedure for unfolding the true distribution from experimental data is presented. Machine learning methods are applied for simultaneous identification of an apparatus function and solving of an inverse problem. A priori information about the true distribution ... More