No Arabic abstract
Sterns diatomic sequence with its intrinsic repetition and refinement structure between consecutive powers of $2$ gives rise to a rather natural probability measure on the unit interval. We construct this measure and show that it is purely singular continuous, with a strictly increasing, Holder continuous distribution function. Moreover, we relate this function with the solution of the dilation equation for Sterns diatomic sequence.
Let a(n) be the Sterns diatomic sequence, and let x1,...,xr be the distances between successive 1s in the binary expansion of the (odd) positive integer n. We show that a(n) is obtained by evaluating generalized Chebyshev polynomials when the variables are given the values x1+1, ..., xr+1, and we derive a formula expressing the same polynomials in terms of sets of increasing integers of alternating parity. We also show that a(n) = Det(Ir + Mr), where Ir is the rxr identity matrix, and Mr is the rxr matrix that has x1,...,xr along the main diagonal, then all 1s just above and below the main diagonal, and all the other entries are 0.
In this work we give general conditions under which a $C^0$ perturbation of an expansive homeomorphim with specification property has an unique Bowen measure, that is, there is an ergodic probability measure which is the unique measure maximizing the topological entropy. We apply these conditions to show that several derived from Anosov diffeomorphims have a unique Bowen measure.
Let $f_0(z) = exp(z/(1-z))$, $f_1(z) = exp(1/(1-z))E_1(1/(1-z))$, where $E_1(x) = int_x^infty e^{-t}t^{-1}{,d}t$. Let $a_n = [z^n]f_0(z)$ and $b_n = [z^n]f_1(z)$ be the corresponding Maclaurin series coefficients. We show that $a_n$ and $b_n$ may be expressed in terms of confluent hypergeometric functions. We consider the asymptotic behaviour of the sequences $(a_n)$ and $(b_n)$ as $n to infty$, showing that they are closely related, and proving a conjecture of Bruno Salvy regarding $(b_n)$. Let $rho_n = a_n b_n$, so $sum rho_n z^n = (f_0,odot f_1)(z)$ is a Hadamard product. We obtain an asymptotic expansion $2n^{3/2}rho_n sim -sum d_k n^{-k}$ as $n to infty$, where the $d_kinmathbb Q$, $d_0=1$. We conjecture that $2^{6k}d_k in mathbb Z$. This has been verified for $k le 1000$.
The ability of the organism to distinguish between various stimuli is limited by the structure and noise in the population code of its sensory neurons. Here we infer a distance measure on the stimulus space directly from the recorded activity of 100 neurons in the salamander retina. In contrast to previously used measures of stimulus similarity, this neural metric tells us how distinguishable a pair of stimulus clips is to the retina, given the noise in the neural population response. We show that the retinal distance strongly deviates from Euclidean, or any static metric, yet has a simple structure: we identify the stimulus features that the neural population is jointly sensitive to, and show the SVM-like kernel function relating the stimulus and neural response spaces. We show that the non-Euclidean nature of the retinal distance has important consequences for neural decoding.
For a prime $pge 5$ let $q_0,q_1,ldots,q_{(p-3)/2}$ be the quadratic residues modulo $p$ in increasing order. We study two $(p-3)/2$-periodic binary sequences $(d_n)$ and $(t_n)$ defined by $d_n=q_n+q_{n+1}bmod 2$ and $t_n=1$ if $q_{n+1}=q_n+1$ and $t_n=0$ otherwise, $n=0,1,ldots,(p-5)/2$. For both sequences we find some sufficient conditions for attaining the maximal linear complexity $(p-3)/2$. Studying the linear complexity of $(d_n)$ was motivated by heuristics of Caragiu et al. However, $(d_n)$ is not balanced and we show that a period of $(d_n)$ contains about $1/3$ zeros and $2/3$ ones if $p$ is sufficiently large. In contrast, $(t_n)$ is not only essentially balanced but also all longer patterns of length $s$ appear essentially equally often in the vector sequence $(t_n,t_{n+1},ldots,t_{n+s-1})$, $n=0,1,ldots,(p-5)/2$, for any fixed $s$ and sufficiently large $p$.