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At least 649 records · Page 36Linked to original sources
arXiv2021

Maxwell's Demon must remain sebservient to Clausius's statement

Using classical thermodynamics, we argue that Maxwell's demon loses its battle against Clausius as any temperature difference or other thermodynamic forces it creates is immediately compensated by spontaneous counterbalancing flows that bring about equilibration by slower particles in principle. Being constrained by these spontaneously generated equilibration processes in which he actively but unwittingly participates, the demon is incapable of destroying equilibrium and violating the second law. In fact, our investigation shows that he is unintentionally designed to support it, and does not alter the temperature.

physics.class-ph↗
arXiv2022

The Economics of Interstellar Flight

Large scale directed energy offers the possibility of radical transformation in a variety of areas, including the ability to achieve relativistic flight that will enable the first interstellar missions, as well as rapid interplanetary transit. In addition, the same technology will allow for long-range beamed power for ion, ablation, and thermal engines, as well as long-range recharging of distant spacecraft, long-range and ultra high bandwidth laser communications, and many additional applications that include remote composition analysis, manipulation of asteroids, and full planetary defense. Directed energy relies on photonics which, like electronics, is an exponentially expanding growth area driven by diverse economic interests that allows transformational advances in space exploration and capability. We have made enormous technological progress in the last few years to enable this long-term vision. In addition to the technological challenges, we must face the economic challenges to bring the vision to reality. The path ahead requires a fundamental change in the system designs to allow for the radical cost reductions required. To afford the full-scale realization of this vision we will need to bring to fore integrated photonics and mass production as a path forward. Fortunately, integrated photonics is a technology driven by vast consumer need for high speed data delivery. We outline the fundamental physics that drive the economics and derive an analytic cost model that allows us to logically plan the path ahead.

econ.GN↗
arXiv2023

Ramanujan summation and the Casimir effect

Srinivasa Ramanujan was a great self-taught Indian mathematician, who died a century ago, at the age of only 32, one year after returning from England. Among his numerous achievements is the assignment of sensible, finite values to divergent series, which correspond to Riemann's $ζ$-function with negative integer arguments. He hardly left any explanation about it, but following the few hints that he gave, we construct a direct justification for the best known example, based on analytic continuation. As a physical application of Ramanujan summation we discuss the Casimir effect, where this way of removing a divergent term corresponds to the renormalization of the vacuum energy density, in particular of the photon field. This leads to the prediction of the Casimir force between conducting plates, which has now been accurately confirmed by experiments. Finally we review the discussion about the meaning and interpretation of the Casimir effect. This takes us to the mystery surrounding the magnitude of Dark Energy.

physics.hist-ph↗
arXiv2022

The gravitational potential energy of the Great Pyramid

The calculation of the energy required to raise a constituent block of the Khufu pyramid and the knowledge of the mechanical energy that a worker in charge of the lifting of the blocks can produce per working day allows an estimate of the minimum number of workers. necessary for the establishment of a base of the pyramid. It emerges that this number is limited to a maximum of less than 2,000 workers over a working season, ie less than 200 present each day simultaneously on the site. In addition, the calculation of the flow of blocks leads to the ineluctable conclusion that the construction could only be done in a massively parallel working mode, undermining the hypothesis very often put forward of the use of ramps to convey the blocks to their final destination.

physics.pop-ph↗
arXiv2022

Gravity-Assist as a Solution to Save Earth from Global Warming

Global warming is one of the problems of human civilization and decarbonization policy is the main solution to this problem. In this work, we propose using the gravity-assist by the asteroids to increase the orbital distance of the Earth from the Sun. We can manipulate the orbit of asteroids in the asteroid belt by solar sailing and propulsion engines to guide them towards the Mars orbit and a gravitational scattering can put asteroids in a favorable direction to provide an energy loss scattering from the Earth. The result would be increasing the orbital distance of the earth and consequently cooling down the Earth's temperature. We calculate the increase in the orbital distance of the earth for each scattering and investigate the feasibility of performing this project.

astro-ph.EP↗
arXiv2022

Futurama, Marvel's Supervillains and Boltzmann Brains / Futurama, los Supervillanos del Universo Marvel y los Cerebros de Boltzmann

In this article I will explore some uses of the concept of Boltzmann brains in comics (Marvel's The Incredible Hercules), an animated sitcom (Futurama) and a film (Guardians of the Galaxy Vol. 2). Previous similar uses of the concept (before Boltzmann brains were named as such) will be traced, and potential influences on these artistic outlets will be analysed. I will also explain how the concept was used in a novel published in 2018 by Ediciones Ayarmanot in Buenos Aires (La inevitable resurrección de los cerebros de Bolzmann, to be published in English as "Iridio Ennui vs. the Boltzmann brains"). After briefly reviewing the second law of thermodynamics and the concept of Boltzmann brains, the paper analyses the four artistic instances in which has been used, answering two key questions: a) How entities who (in theory) appear in the foam of interstellar space and suddenly disappear are presented in the fictional scenario? b) How the plot justifies that Boltzmann brains could exist for a time long enough to allow them to become viable fictional characters?

physics.pop-ph↗
arXiv2022

Multistatic radar measurements of Unidentified Aerial Phenomena by cell and open access radio networks

Measurements of a wide variety of aerial phenomena such as drones, birds, planes, and other aerial objects can in principle be obtained from open access radio detection and ranging equipment. Passive strategies involve existing cell towers as transmitters and cell phones as receivers. Another active possibility is the creation of a multistatic, possibly phased array, network of transmission and receiving stations by open-source realizations such as GNU radio. We also suggest provision of uncorrelated targets or anomalies from existing military sources.

physics.pop-ph↗
arXiv2022

Pushing the precision frontier for gravitational waves

Pushing the precision frontier for gravitational waves is one of the most urgent tasks in theoretical physics today, in light of the increasing influx of data from a rapidly growing worldwide network of gravitational-wave detectors.

physics.pop-ph↗
arXiv2023

Anthropic constraint on transient variations of fundamental constants

The anthropic principle implies that life can emerge and be sustained only in a narrow range of values of fundamental constants. Here we show that anthropic arguments can set powerful constraints on {\em transient} variations of the fine-structure constant $α$ over the past 4 billion years since the appearance of lifeforms on Earth. We argue that the passage through Earth of a macroscopic dark matter clump with a value of $α$ inside differing substantially from its nominal value would make Earth uninhabitable. We demonstrate that in the regime of extreme variation of $α$, the periodic table of elements is truncated, water fails to serve as a universal solvent, and protons become unstable. Thereby, the anthropic principle constrains the likelihood of such encounters on a 4-billion-year timescale. This enables us to improve existing astrophysical bounds on certain dark matter model couplings by several orders of magnitude.

physics.atom-ph↗
arXiv2022

Quantum Computing and the Future Internet

One of the biggest concerns among cybersecurity professionals these days is the hype around quantum computing, its incomprehensible power, and its implications. The advancement in quantum computing has the potential to revolutionize our daily lives, but it can also completely break down the Internet as we know it. Mathematicians and physicists have developed algorithms based on quantum computing, which can change the Internet security paradigm. This article discusses quantum computing key concepts, with a special focus on quantum Internet, quantum key distribution, and related challenges.

physics.pop-ph↗
arXiv2022

Soccer: a quantitative analysis of team resilience and the miracle of Bern

Resilience is the ability to positively respond to adversity. It has been studied in psychology for several decades, with focus on how individuals overcome traumata or cope with setbacks and obstacles in their professional career. Research on resilience in the sport context is rather new. Activities are based on insights that in highly competitive environments, tiny effects tip the scales. A key question of measuring resilience in sports is what parameters to measure. Here a novel concept is proposed to measure the resilience of soccer teams. The relative frequency of matches is determined, where a soccer team, which is initially trailing by 2 goals, finally succeeds to win the match or at least to reach a draw. The analysis is applied to the last 59 seasons of the German premier soccer league Bundesliga. The empirical data are compared with a theoretical model derived from Poisson distributions. It is shown how leading teams in the premier soccer league differ from the average with respect to resilience, which provides further insights into the hidden secrets of top soccer teams.

stat.AP↗
arXiv2022

What is Time? -- Thoughts of a Physicist

Discussion of some aspects of the concept of time for a general audience: nature of time, A- and B-series, time in physics, the "now", measurement of time, definition of time units, time's arrow, relativity of time, relativity of simultaneity.

physics.hist-ph↗
arXiv2024

The Parking Lot Planet

We give conditions for an exoplanetary system to function as an ideal amusement park/vacation resort (with its separate parking lot, of course); in case of massive human interplanetary colonization. Our considerations stem from the fact that an amusement park needs a parking lot of roughly the same surface area, thus the best option for its construction would be a system with at least 2 planets close to each other for easy tourist transportation. We also discuss the likelihood of finding such a system out there to cut down on construction costs.

physics.pop-ph↗
arXiv2024

Finding the ET Signal from the Cosmic Noise

This paper highlights a methodological approach designed to enhance the search for extraterrestrial intelligence (SETI) by hypothesizing that a transmission technosignature would likely have two features: 1) be wideband in the microwave or higher frequency range that originates from a hub within a supposed ET interplanetary navigation/communication (nav/comm) network, and 2) contain x-ray pulsar-based navigation (XNAV) metadata. Potential contributions to the field include improved accuracy in finding transmission technosignatures and other technosignatures in the electromagnetic spectrum, a common standard in reaching a Schelling Point (a mutual realization of how we and ETs can find each other), and operationalizing models such as the Drake Equation.

physics.pop-ph↗
arXiv2022

Do anthropic arguments really work?

The anthropic explanation for the peculiarly small observed value of the cosmological constant $Λ_{\rm obs}$ argues that this value promotes the formation of stars, planets, and ultimately of observers such as ourselves. I show that a recent analytic model of cosmic star formation predicts that although $Λ_{\rm obs}$ maximises the overall efficiency of star formation in the universe, the probability of generating observers peaks at $\sim400-500 \, Λ_{\rm obs}$. These preliminary results suggest that an immediate connection between star formation efficiency and observers' generation is not straightforward, and highlight the subtleties involved with the application of anthropic reasoning.

astro-ph.CO↗
arXiv2022

Retrospective Observation of Ball Lightning

Ball lightning is a very rarely observed phenomenon that makes it extremely difficult to characterize scientifically. Eye-witness accounts of ball lightning that describe many features in common have been variously recorded for centuries. This note is an account of my observation of ball lightning almost five decades ago. Although it is mostly a compendium of recalled impressions (no photos or videos), it so happens that certain corroborating information has since become available on the Internet and supports the conclusion that I did indeed observe ball lightning. This note also helps to explain why obtaining hard evidence is even more difficult than is generally assumed. Paradoxically, the inordinate delay between the original observation and this documentation may actually have enhanced its scientific merit.

physics.pop-ph↗
arXiv2022

Engineering an Interstellar Communications Network by Deploying Relay Probes

We develop a model for an interstellar communication network that is composed of relay nodes that transmit diffraction-limited beams of photons. We provide a multi-dimensional rationale for such a network of communication in lieu of interstellar beacons. We derive a theoretical expression for the bit rate of communication based on fundamental physics, constrained by the energy available for photons and the diffraction of the beam that dilutes the information by the inverse square law. We find that meter-scale probes are severely limited in their bit rate, under 1 Gbps, over distances of a light year. However, that bit rate is proportional to the 4th power of the size of the optics that transmit and receive the photons, and inversely proportional to the square of the distance between them, thus favoring large optics and short separations between nodes. The optimized architecture of interstellar communication consists of a network of nodes separated by sub-light-year distances and strung out between neighboring stars.

physics.pop-ph↗