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At least 55 records · Page 3Linked to original sources
arXiv2009

Sociology of Modern Cosmology

Certain results of observational cosmology cast critical doubt on the foundations of standard cosmology but leave most cosmologists untroubled. Alternative cosmological models that differ from the Big Bang have been published and defended by heterodox scientists; however, most cosmologists do not heed these. This may be because standard theory is correct and all other ideas and criticisms are incorrect, but it is also to a great extent due to sociological phenomena such as the "snowball effect" or "groupthink". We might wonder whether cosmology, the study of the Universe as a whole, is a science like other branches of physics or just a dominant ideology.

physics.gen-ph↗
arXiv2009

The Muisca Calendar: An approximation to the timekeeping system of the ancient native people of the northeastern Andes of Colombia

The aim of this project is to review and expand upon the model proposed by Father Jose Domingo Duquesne de la Madrid (1745-1821) regarding the calendar of the ancient Muisca culture of the central Colombia. This model was dismissed by scholars in the late 19th century, calling it just a simple invention of a clergyman; however, a detailed analysis of Duquesne's work shows that his interpretation of the timekeeping system was based on information given to him by indigenous informers. Based on his work, we can be derive somewhat indirectly, some aspects of the calendar that apparently were not understood by the priest. This confirms that such a system was not his own invention. Ethnohistorical and archaeological evidence provide support for Duquesne's calendar model. Massive Muisca ceremonies described by 16th century Spanish chroniclers, is examined and; the occurrence of such ceremonies seem to match the astronomical cycle of conjunctions of the planets Jupiter and Saturn, wich also agrees with the 60-year span described by Duquesne as the Muisca Acrotom Century. Archaeological artifacts, such as a carved stone found in the village of Choachi (Cundinamarca) that shows numerical elements supports Duquesne's model that suggests this stone was a calendar calculation tool for Muisca priests.

physics.hist-ph↗
arXiv2008

50 Years of Computer Simulation -- a Personal View

In the half century since the 1950s computer simulation has transformed our understanding of physics. The rare, expensive, slow, and bulky mainframes of World War II have given way to today's millions of cheap, fast, desksized workstations and personal computers. As a result of these changes, the theoretical formal view of physics has gradually shifted, so as to focus on the pragmatic and useful. General but vague approaches are being superceded by specific results for definite models. During this evolving change of emphasis I learned, developed, and described my simulation skills at Michigan, at Duke, at Livermore, and in Nevada, while forming increasingly wide-ranging contacts around the world. Computation is now pervasive in all the scientific fields. My own focus has been on the physics of particle simulations, mainly away from equilibrium. I outline my particle work here. It has led me to a model-based understanding of both equilibrium and nonequilibrium physics. There are still some gaps. There is still much to do.

nlin.CD↗
arXiv2009

Regarding the Potential Impact of Double Star Observations on Conceptions of the Universe of Stars in the Early 17th Century

Galileo Galilei believed that stars were distant suns whose sizes, measured via his telescope, were a direct indication of distance -- fainter stars (appearing smaller in the telescope) were farther away than brighter ones. Galileo argued in his Dialogue that telescopic observation of a chance alignment of a faint (distant) and bright (closer) star would reveal annual parallax, if such double stars could be found. This would provide support both for Galileo's ideas concerning the nature of stars and for the motion of the Earth. However, Galileo actually made observations of such double stars, well before publication of the Dialogue. We show that the results of these observations, and the likely results of observations of any double star that was a viable subject for Galileo's telescope, would undermine Galileo's ideas, not support them. We argue that such observations would lead either to the more correct conclusion that stars were sun-like bodies of varying sizes which could be physically grouped, or to the less correct conclusion that stars are not sun-like bodies, and even to the idea that the Earth did not move. Lastly, we contrast these conclusions to those reached through applying Galileo's ideas to observations of visible stars as a whole.

physics.hist-ph↗
arXiv2008

Gravity from strings: personal reminiscence on early developments

I discuss the early developments of string theory with respect to its connection with gauge theory and general relativity from my own perspective. The period covered is mainly from 1969 to 1974, during which I became involved in research on dual string models as a graduate student. My thinking towards the recognition of string theory as an extended quantum theory of gravity is described. Some retrospective remarks on my later works related to this subject are also given.

hep-th↗
arXiv2009

Planck's blackbody radiation law: Presentation in different domains and determination of the related dimensional constants

In this paper the Planck function is derived in the frequency domain using the method of oscillators. It is also presented in the wavelength domain and in the wave number domain. The latter is mainly used in spectroscopy for studying absorption and emission by gases. Also the power law of Stephan and Boltzmann is derived for these various domains. It is shown that this power law is generally independent of the domain in which the Planck function is presented. A formula for the filtered spectrum is also given and expressed in the sense of the power law of Stefan and Boltzmann. Furthermore, based on Wien's displacement relationship, it is argued that the wavelength at which the maximum of the Planck function presented in the wavelength domain occurs differs from that of the maxima of the other domains by a factor of 1.76. As Planck determined his elementary quantum of action, eventually called the Planck constant, and the Boltzmann constant using Wien's displacement relationship formulated for the wavelength domain, it is shown that the values of these fundamental constants are not affected by the choice of domain in which the Planck function is presented. Finally, the origin of the Planck constant is discussed.

physics.hist-ph↗
arXiv2009

Visible Stars as Apparent Observational Evidence in Favor of the Copernican Principle in the Early 17th Century

The Copernican Principle (which says the Earth and sun are not unique) should have observational consequences and thus be testable. Galileo Galilei thought he could measure the true angular diameters of stars with his telescope; according to him, stars visible to the naked eye range in diameter from a fraction of a second to several seconds of arc. He used this and the Copernican Principle assumption that stars are suns as a method of determining stellar distances. The expected numbers of naked eye stars brighter than a given magnitude can be calculated via Galileo's methods; the results are consistent with data obtained from counting naked eye stars. Thus the total number of stars visible to the naked eye as a function of magnitude would appear to Galileo to be data supporting the Copernican Principle.

physics.hist-ph↗
arXiv2009

A simple resolution of Stokes' paradox?

This paper proposes a solution to Stokes' paradox for asymptotically uniform viscous flow around a cylinder. The existence of a {\it global} stream function satisfying a perturbative form of the two-dimensional Navier-Stokes equations for low Reynolds number is established. This stream function satisfies the appropriate boundary conditions on both the cylinder and at infinity, but nevertheless agrees with Stokes' original results at finite radius as the Reynolds number tends to zero. The Navier-Stokes equations are satisfied to a power-log power of the Reynolds number. The drag on the cylinder is calculated from first principles and the free parameter of the approach can be chosen to give good agreement with data on drag. In this revised working paper we put our approach on a firmer mathematical basis using the Helmholtz-Laplace equation as a linear approximation to the Navier-Stokes system. In so doing we demonstrate the instability of the original paradox. We also demonstrate the absence of a paradox of Stokes-Whitehead class, and give further theoretical constraints on the free parameters of the model.

physics.flu-dyn↗
arXiv2010

Bayesian reasoning in cosmology

We discuss epistemological and methodological aspects of the Bayesian approach in astrophysics and cosmology. The introduction to the Bayesian framework is given for a further discussion concerning the Bayesian inference in physics. The interplay between the modern cosmology, Bayesian statistics, and philosophy of science is presented. We consider paradoxes of confirmation, like Goodman's paradox, appearing in the Bayesian theory of confirmation. As in Goodman's paradox the Bayesian inference is susceptible to some epistemic limitations in the logic of induction. However Goodman's paradox applied to cosmological hypotheses seems to be resolved due to the evolutionary character of cosmology and accumulation new empirical evidences. We argue that the Bayesian framework is useful in the context of falsificability of quantum cosmological models, as well as contemporary dark energy and dark matter problem.

physics.data-an↗
arXiv2009

Tribute to Francisco (Paco) Yndurain

This part of the talk aims to present briefly the biodata and the exceptional career of Paco Yndurain who left us suddenly in June 2008. The scientific part: Light Scalar Mesons in QCD is published in the proceedings of QCD 08 (Montpellier 7-12th july 2008: arXiv:0811.0563 [hep-ph]).

physics.hist-ph↗
arXiv2009

Living with Infinities

This is the written version of a talk given in memory of Gunnar Källén, at the Departments of Theoretical Physics, Physics, and Astronomy of Lund University on February 13, 2009. It will be published in a collection of the papers of Gunnar Källén, edited by C. Jarlskog and A. C. T. Wu. I discuss some of Källén's work, especially regarding the problem of infinities in quantum field theory, and recount my own interactions with him. In addition, I describe for non-specialists the current status of the problem, and present my personal view on how it may be resolved in the future.

hep-th↗
arXiv2009

Topography, astronomy and dynastic history in the alignments of the pyramid fields of the Old Kingdom

It is known since the 19 century that in the layout of the pyramid field of the pharaohs of the 4 th Egyptian dynasty at Giza, a main axis exists. Indeed, the south-east corners of these monuments align towards the site of the temple of Heliopolis, which was plainly visible in ancient times. It was later discovered that a similar situation occurs in the main pyramid field of the subsequent dynasty at Abu Sir. Here, the northwest corners of three chronologically successive pyramids again voluntarily align towards Heliopolis. However, the temple was in this case not visible, due to the rock outcrop today occupied by the Cairo citadel which blocks the view. In the present paper, a interdisciplinary approach based on historical, topographical and archaeoastronomical analysis is developed in an attempt at understanding such peculiar features, which governed from the very beginning the planning of these wonderful monuments. A general pattern actually arises, which appears to have inspired the choice of the sites and the disposition on the ground of almost all the funerary complexes of the kings during the Old Kingdom. In particular, this pattern helps to explain the choices in the location of the funerary complexes of Niuserre in Abusir and of Unas in Saqqara.

physics.hist-ph↗
arXiv2009

Temporal Platonic Metaphysics

In this essay we describe a platonic metaphysics where time is a fundamental idea such that the passage of time is independent of observers and the laws of physics. Furthermore, time serves to distinguish between a real and an abstract universe, where a real universe is an appropriatelly ordered set of ideas in time, while an abstract universe is such a set outside of time. We allow for non-computable and non-mathematical ideas to be part of our model of the universe in order to include intelligent observers. The part of the universe which can be described by mathematics corresponds to a mathematical structure in Tegmark's sense, while the non-mathematical part can be described by a human language. We describe the mind-brain connection in our framework, and show that it resolves the problem of obtaining abstract knowledge in platonism. We briefly discuss how different interpretations of Quantum Mechanics can be implemented in our framework and point out some physics implications, most notably that the time travel would be impossible.

physics.hist-ph↗
arXiv2009

Pioneer Women in Chaos Theory

The general public has been made aware of the research field of "chaos" by the book of that title by James Gleick. This paper will focus on the achievements of Sonya Kovalevskaya, Mary Cartwright, and Mary Tsingou, whose pioneer works were not mentioned in Gleick's book.

physics.hist-ph↗
arXiv2009

Time, Space and Structure in Ancient India

Textual and archaeological sources are used to provide a synoptic vision of the universe in India. This vision was based on an assumed equivalence of the outer and the inner cosmoses and it is embodied in architecture, music, and art. It provides an archaeoastronomical window on Indian monumental architecture.

physics.hist-ph↗
arXiv2009

Einstein's Apple and Relativity's Gravitational Field

The foundations of Einstein's first (1907) principle of equivalence are explored and their consequences are stated in terms of invariance under generalized Lorentz transformations, first explored by Hessenberg.

physics.hist-ph↗
arXiv2009

Lorenz fields convey energy as Nadelstrahlung

Gauge transformations leave only specific Maxwell fields unchanged. To reveal more, I develop Lorenz field equations for superposed, sourced and unsourced, wave function potentials. In this Maxwell form system, the Lorenz condition is charge conservation. This allows me to define three transformation classes that screen for Lorenz relevance. Nongauge, sans gauge function, Lorentz conditions add polarization fields. These enable emergent, light-like radiation. That from Lissajous potentials is Nadelstrahlung. It conveys energy localized like particles at charge conserving, progressive phase points. Such rays escape discovery in modern Maxwell fields where gauge transformations suppress the polarizations.

physics.gen-ph↗