The Black Hole Entropy Can Be Smaller than A/4

The coupling of a Nambu-Goto string to gravity allows for Schwarzschild black holes whose entropy to area relation is $S=(A/4)(1-4\mu)$, where $\mu$ is the string tension.Comment: LaTeX, 9 pages, final version to appear in Phys.Lett.

On the use of semantic awareness to limit overfitting in genetic programming

Dissertation presented as the partial requirement for obtaining a Master's degree in Data Science and Advanced AnalyticsMachine learning and statistics provide powerful tools to solving problems of many different shapes. But with the algorithms searching for approximations the problem of overfitting remains present. Genetic Programming describes an algorithmic approach that is likely to produce overfitting solutions. Thus, in order to lessen the risk of overfitting and increasing the generalization ability of genetic programming the use of semantic information is assessed in different ways. A multi-objective system driving the population away from overfitting solutions based on semantic distance is presented alongside alternatives and extensions. The extensions include the use of the semantic signature to increase the amount of information available to the system, as well as the consideration to replace the validation dataset. It is on the one hand concluded that the described approaches and none of the extensions have a positive impact on the generalization ability. But on the other hand it seems that the semantics do contain enough information to appropriately discriminate between overfitting and not overfitting individuals

Socio-economic disparities and COVID-19 in the USA

COVID-19 is not a universal killer. We study the spread of COVID-19 at the county level for the United States up until the 15$^{th}$ of August, 2020. We show that the prevalence of the disease and the death rate are correlated with the local socio-economic conditions often going beyond local population density distributions, especially in rural areas. We correlate the COVID-19 prevalence and death rate with data from the US Census Bureau and point out how the spreading patterns of the disease show asymmetries in urban and rural areas separately and is preferentially affecting the counties where a large fraction of the population is non-white. Our findings can be used for more targeted policy building and deployment of resources for future occurrence of a pandemic due to SARS-CoV-2. Our methodology, based on interpretable machine learning and game theory, can be extended to study the spread of other diseases.Comment: 10 pages, 5 figures and 1 tabl

Efecto tóxico del cobre en poblaciones naturales de picoplancton aisladas, procedentes de distintas localizaciónes geográficas

9 páginas, 9 figuras, 2 tablas.[EN] In an approach to understand more about copper toxicity effects on marine microalgae, 72-h growth inhibition toxicity tests were followed on natural picophytoplanktonic populations belonging to different coastal and oceanic geographic locations (Mediterranean Sea and Atlantic Ocean) covering, at an approximate longitude of 30ºW, latitudes from 32º14´S to 29º10´N. Analyses of samples established different predominant populations for different locations. Copper toxicity tests showed a group of cyanobacteria isolated from coastal samples that were the most sensitive, and a second group of picoeukaryotes collected from the Atlantic Ocean surface, which were more tolerant to copper. The use of flow cytometry for studying copper toxic effects provided a variety of information on cell parameters in addition to cellular density. In particular, an established increase in copper tolerance with increase of cell size was observed in cyanobacteria, but it was not clearly followed in picoeukaryotes. This study aims to relate copper tolerance to the geographic location sites of sampling collection. The results obtained establish that other factors such as cell size, proximity to the coast and copper concentration in situ are considered to have a greater influence than the fact of belonging to a determined location site.[ES] Con el fin de estudiar el efecto tóxico del cobre en las microalgas marinas, se llevaron a cabo ensayos de toxicidad (72 h) con poblaciones naturales de picofitoplancton. Poblaciones procedentes de distintas localizaciones geográficas (mar Mediterráneo y océano Atlántico), cubriendo, aproximadamente en la longitud de 30ºO, latitudes comprendidas entre 32º14´S y 29º10´N. El análisis inicial de las muestras permitió distinguir las poblaciones predominantes de cada estación de muestreo, a exponer en los ensayos de toxicidad. En resumen, un grupo de cianobacterias procedentes de las muestras costeras resultaron ser las más sensibles, y un segundo grupo de picoeucariotas, tomadas de la superficie del océano Atlántico, las más tolerantes al cobre. El análisis del ensayo se llevó a cabo mediante citometría de flujo lo que permitió estudiar otros parámetros celulares, aparte de la densidad celular. Pudiendo observar, en el caso de las cianobacterias, un incremento de la tolerancia al cobre con incremento de su tamaño celular; que no resultó tan evidente en el caso del grupo de picoeucariotas. Finalmente, al relacionar la tolerancia al cobre con las poblaciones procedentes de distintas localizaciones geográficas de muestreo podemos concluir que, otros factores, tales como: el tamaño celular, proximidad a costa, o concentraciones del metal in situ, pueden tener una mayor influencia que la localización geográfica de la población.This work has been supported by the Spanish CICYT (Spanish Commission for Research and Development) in the contract of the project PETRI 95-0971.Peer reviewe

Numerical evidence for the maximum number of mutually unbiased bases in dimension six

The question of determining the maximal number of mutually unbiased bases in dimension six has received much attention since their introduction to quantum information theory, but a definitive answer has still not been found. In this paper we move away from the traditional analytic approach and use a numerical approach to attempt to determine this number. We numerically minimise a non-negative function of a set of N+1 orthonormal bases in dimension d which only evaluates to zero if the bases are mutually unbiased. As a result we find strong evidence that (as has been conjectured elsewhere) there are no more than three mutually unbiased bases in dimension six.Comment: 4 pages, 2 figures, some minor changes mad

Green energy in the service of mankind

This paper presents the project called “Vetrosvet” that has been carried out in Tomsk region by students of Tomsk Polytechnic University. This project has a great value as it is focused on popularizing green energy and renewable sources in Russia and, mainly, in the Tomsk region. Tomsk region is known as a center of innovation technology. That is why the region has been chosen for caring out the project. Moreover, the usage of wind turbines is more effective than solar panels in this region. It can be explained by the small amount of sunny days in Siberian region. The wind turbines are put together in the development laboratory at Tomsk Polytechnic University. The results of this project are presented in this paper

A CMOS 0.8- µm transistor-only 1.63-MHz switched-current bandpass ΣΔ modulator for AM signal A/D conversion

This paper presents a CMOS 0.8-/spl mu/m switched-current (SI) fourth-order bandpass /spl Sigma//spl Delta/ modulator (BP-/spl Sigma//spl Delta/M) IC capable of handling signals up to 1.63 MHz with 105-bit resolution and 60-mW power consumption from a 5-V supply voltage. This modulator Is intended for direct A/D conversion of narrow-band signals within the commercial AM band, from 530 kHz to 1.6 MHz. Its architecture is obtained by applying a low-pass-to-bandpass transformation (z/sup -1//spl rarr/-z/sup -2/) to a 1-bit second-order low-pass /spl Sigma//spl Delta/ modulator (LP-/spl Sigma//spl Delta/M). The design of basic building blocks is based upon a detailed analysis of the influence of SI errors on the modulator performance, followed by design optimization. Memory-cell errors have been identified as the dominant ones. In order to attenuate these errors, fully differential regulated-folded cascode memory cells are employed. Measurements show a best SNR peak of 65 dB for signals of 10-kHz bandwidth and an intermediate frequency (IF) of 1.63 MHz. A correct noise-shaping filtering is achieved with a sampling frequency of up to 16 MHz.This work has been supported by the Spanish CICYT Project TIC 97-0580

Quantitative wave-particle duality and non-erasing quantum erasure

The notion of wave-particle duality may be quantified by the inequality V^2+K^2 <=1, relating interference fringe visibility V and path knowledge K. With a single-photon interferometer in which polarization is used to label the paths, we have investigated the relation for various situations, including pure, mixed, and partially-mixed input states. A quantum eraser scheme has been realized that recovers interference fringes even when no which-way information is available to erase.Comment: 6 pages, 4 figures. To appear in Phys. Rev.