Found 1014 results, showing the newest relevant preprints. Sort by relevancy only.Update me on new preprints

The role of molecular filaments in the origin of the prestellar core mass function and stellar initial mass function

The origin of the stellar initial mass function (IMF) is one of the most debated issues in astrophysics. Expand abstract.

The origin of the stellar initial mass function (IMF) is one of the most debated issues in astrophysics. Here, we explore the possible link between the quasi-universal filamentary structure of star-forming molecular clouds and the origin of the IMF. Based on our recent comprehensive study of filament properties from Herschel Gould Belt survey observations (Arzoumanian et al.), we derive, for the first time, a good estimate of the filament mass function (FMF) and filament line mass function (FLMF) in nearby molecular clouds. We use the observed FLMF to propose a simple toy model for the origin of the prestellar core mass function (CMF), relying on gravitational fragmentation of thermally supercritical but virialized filaments. We find that the FMF and the FLMF have very similar shapes and are both consistent with a Salpeter-like

**power**-**law**function (d$N$/dlog$M_{\rm line} \propto M_{\rm line}^{-1.5\pm0.1}$) in the regime of thermally supercritical filaments ($M_{\rm line} > 16\, M_\odot$/pc). This is a remarkable result since, in contrast, the mass distribution of molecular clouds and clumps is known to be significantly shallower than the Salpeter**power**-**law**IMF, with d$N$/dlog$M_{\rm cl} \propto M_{\rm cl}^{-0.7}$. Since the vast majority of prestellar cores appear to form in thermally transcritical or supercritical filaments, we suggest that the prestellar CMF and by extension the stellar IMF are at least partly inherited from the FLMF through gravitational fragmentation of individual filaments.134 days ago

5/10 relevant

arXiv

5/10 relevant

arXiv

Universality of **power**-**law** exponents by means of maximum likelihood
estimation

By means of the procedure exposed in this manuscript, it has been found that the Gutenberg-Richter

**law**for earthquakes and charcoal labquakes can be characterized by the same**power**-law exponent. Expand abstract.**Power**-

**law**type distributions are extensively found when studying the behaviour of many complex systems. However, due to limitations in data acquisition, empirical datasets often only cover a narrow range of observation, making it difficult to establish

**power**-

**law**behaviour unambiguously. In this work we present a statistical procedure to merge different datasets with the aim of obtaining a broader fitting range for the statistics of different experiments or observations of the same system or the same universality class. This procedure is applied to the Gutenberg-Richter

**law**for earthquakes and for synthetic earthquakes (acoustic emission events) generated in the laboratory: labquakes. Different earthquake catalogs have been merged finding a Gutenberg-Ricther

**law**holding for more than eight orders of magnitude in seismic moment. The value of the exponent of the energy distribution of labquakes depends on the material used in the compression experiments. By means of the procedure exposed in this manuscript, it has been found that the Gutenberg-Richter

**law**for earthquakes and charcoal labquakes can be characterized by the same

**power**-

**law**exponent.

135 days ago

10/10 relevant

arXiv

10/10 relevant

arXiv

Cities and space: Common **power** **laws** and spatial fractal structures

We find that city size distributions in different parts of these spatial hierarchies exhibit

**power****laws**that are again far more similar than would be expected by chance alone -- suggesting the existence of a spatial fractal structure. Expand abstract. City size distributions are known to be well approximated by

**power****laws**across a wide range of countries. But such distributions are also meaningful at other spatial scales, such as within certain regions of a country. Using data from China, France, Germany, India, Japan, and the US, we first document that large cities are significantly more spaced out than would be expected by chance alone. We next construct spatial hierarchies for countries by first partitioning geographic space using a given number of their largest cities as cell centers, and then continuing this partitioning procedure within each cell recursively. We find that city size distributions in different parts of these spatial hierarchies exhibit**power****laws**that are again far more similar than would be expected by chance alone -- suggesting the existence of a spatial fractal structure.136 days ago

8/10 relevant

arXiv

8/10 relevant

arXiv

Exact analytical expression for the synchrotron radiation spectrum in the Gaussian turbulent magnetic field

We demonstrate that the exact solution for the spectrum of synchrotron radiation from an isotropic population of mono-energetic electrons in turbulent magnetic field with Gaussian distribution of local field strengths can be expressed in the simple analytic form: $\left( \frac{{\rm d} \dot{N}}{{\rm d} \omega} \right)_t = \frac{\alpha}{3} \frac{1}{\gamma^2}... Expand abstract.

We demonstrate that the exact solution for the spectrum of synchrotron radiation from an isotropic population of mono-energetic electrons in turbulent magnetic field with Gaussian distribution of local field strengths can be expressed in the simple analytic form: $\left( \frac{{\rm d} \dot{N}}{{\rm d} \omega} \right)_t = \frac{\alpha}{3} \frac{1}{\gamma^2} \left( 1 + \frac{1}{x^{2/3}} \right) \exp \left( - 2 x^{2/3} \right)$, where $x = \frac{\omega}{\omega_0}\, ; \omega_0 = \frac{4}{3} \gamma^2 \frac{eB_0}{m_e c}\, .$ We use this expression to find approximate synchrotron spectra for

**power**-**law**electron distributions with $\propto \exp\left( -\left[ \gamma/\gamma_0 \right]^\beta\right)$ type high-energy cut-off; the resulting synchrotron spectrum has the exponential cut-off factor with frequency raised to $2\beta/(3\beta+4)$**power**in the exponent. For the**power**-**law**electron distribution without high-energy cut-off, we find the coefficient $a_m$ as a function of the**power**-**law**index, which results in exact expression for the synchrotron spectrum when using monochromatic (i.e., each electron radiates at frequency $\omega_m = a_m \gamma^2 \, \frac{e B_0}{m_e c}$) approximation.139 days ago

7/10 relevant

arXiv

7/10 relevant

arXiv

Prediction in a driven-dissipative system displaying a continuous phase transition

The distribution of event sizes satisfies a

**power****law**with a cutoff for large events. Expand abstract. Prediction in complex systems at criticality is believed to be very difficult, if not impossible. Of particular interest is whether earthquakes, whose distribution follows a

**power****law**(Gutenberg-Richter) distribution, are in principle unpredictable. We study the predictability of event sizes in the Olmai-Feder-Christensen model at different proximities to criticality using a convolutional neural network. The distribution of event sizes satisfies a**power****law**with a cutoff for large events. We find that prediction decreases as criticality is approached and that prediction is possible only for large, non-scaling events. Our results suggest that earthquake faults that satisfy Gutenberg-Richter scaling are difficult to forecast.139 days ago

4/10 relevant

arXiv

4/10 relevant

arXiv

Characterization of the Astrophysical Diffuse Neutrino Flux with IceCube High-Energy Starting Events

The IceCube neutrino observatory has established the existence of an astrophysical diffuse neutrino component above $100$ TeV. Expand abstract.

The IceCube neutrino observatory has established the existence of an astrophysical diffuse neutrino component above $100$ TeV. This discovery was made using the high-energy starting event sample, which uses the outer layer of instrumented volume as a veto to significantly reduce atmospheric background. We present the latest astrophysical neutrino flux measurement using high-energy starting events. This latest iteration of the analysis extends the sample by $1.5$ years for a total of $7.5$ years, updates the event properties with newer models of light transport in the glacial ice, and has an improved systematic treatment. As part of this new analysis, we report on compatibility of our observations with detailed isotropic flux models proposed in the literature as well as the standard generic models such as single, double

**power**-**law**scenarios. We find that none of the tested models are substantially preferred with respect to a single**power****law**.140 days ago

5/10 relevant

arXiv

5/10 relevant

arXiv

Simulating an infinite mean waiting time

Hence, the simulation approach is to directly simulate the process, unless the simulated time exceeds some threshold and if it does, draw the return time from the tail of the

**power****law**. Expand abstract. We consider a hybrid method to simulate the return time to the initial state in a critical-case birth--death process. The expected value of this return time is infinite, but its distribution asymptotically follows a

**power**-law. Hence, the simulation approach is to directly simulate the process, unless the simulated time exceeds some threshold and if it does, draw the return time from the tail of the**power****law**.142 days ago

5/10 relevant

arXiv

5/10 relevant

arXiv

KPZ equation correlations in time

We consider the narrow wedge solution to the Kardar-Parisi-Zhang stochastic PDE under the characteristic $3:2:1$ scaling of time, space and fluctuations. Expand abstract.

We consider the narrow wedge solution to the Kardar-Parisi-Zhang stochastic PDE under the characteristic $3:2:1$ scaling of time, space and fluctuations. We study the correlation of fluctuations at two different times. We show that when the times are close to each other, the correlation approaches one at a

**power**-**law**rate with exponent $2/3$, while when the two times are remote from each other, the correlation tends to zero at a**power**-**law**rate with exponent $-1/3$. We also prove exponential-type tail bounds for differences of the solution at two space-time points. Three main tools are pivotal to proving these results: 1) a representation for the two-time distribution in terms of two independent narrow wedge solutions; 2) the Brownian Gibbs property of the KPZ line ensemble; and 3) recently proved one-point tail bounds on the narrow wedge solution.143 days ago

5/10 relevant

arXiv

5/10 relevant

arXiv

Retroactive Interference Model of **Power**-**Law** Forgetting

A number of experiments under the realm of psychology and experimental neuroscience have described the properties of forgetting in humans and animals, showing that forgetting exhibits a

**power**-**law**relationship with time. Expand abstract. Memory and forgetting constitute two sides of the same coin, and although the first has been rigorously investigated, the latter is often overlooked. A number of experiments under the realm of psychology and experimental neuroscience have described the properties of forgetting in humans and animals, showing that forgetting exhibits a

**power**-**law**relationship with time. These results indicate a counter-intuitive property of forgetting, namely that old memories are more stable than younger ones. We have devised a phenomenological model that is based on the principle of retroactive interference, driven by a multi-dimensional valence measure for acquired memories. The model has only one free integer parameter and can be solved analytically. We performed recognition experiments with long streams of words were performed, resulting in a good match to a five-dimensional version of the model.143 days ago

10/10 relevant

bioRxiv

10/10 relevant

bioRxiv

Retroactive Interference Model of **Power**-**Law** Forgetting

A number of experiments under the realm of psychology and experimental neuroscience have described the properties of forgetting in humans and animals, showing that forgetting exhibits a

**power**-**law**relationship with time. Expand abstract. Memory and forgetting constitute two sides of the same coin, and although the first has been rigorously investigated, the latter is often overlooked. A number of experiments under the realm of psychology and experimental neuroscience have described the properties of forgetting in humans and animals, showing that forgetting exhibits a

**power**-**law**relationship with time. These results indicate a counter-intuitive property of forgetting, namely that old memories are more stable than younger ones. We have devised a phenomenological model that is based on the principle of retroactive interference, driven by a multi-dimensional valence measure for acquired memories. The model has only one free integer parameter and can be solved analytically. We performed recognition experiments with long streams of words were performed, resulting in a good match to a five-dimensional version of the model.144 days ago

10/10 relevant

arXiv

10/10 relevant

arXiv