arXiv subjects

Sascha Vongehr

Publications and source records attributed to Sascha Vongehr.

17 recordsLinked to original sources

arXiv2020

Nano Explosions

At the nano-scale, surface phenomena such as attractive VdW forces strongly dominate; explosions may well be thought impossible. We confirm nano explosions that are important for a fractal (hierarchical, scale invariant) pore structure, greatly increasing pore access. Analyzing only microscope images, image analysis and statistical error reduction algorithms alone provide conclusive evidence of explosively expelled material. The results reconfirm that computer image recognition and statistical analysis are a widely applicable and inexpensive technique for determining parameters which are otherwise unavailable, such as the densities of single nano shapes. The explosion mechanism explains optimum calcination temperatures for cobalt-hydroxide and why slow heating optimizes porosity. Slow heating increases the accessible surface area by 60% with this supercapacitor material.

physics.chem-ph↗

arXiv2015

Purely Mechanical Memristors: Perfect Massless Memory Resistors, the Missing Perfect Mass-Involving Memristor, and Massive Memristive Systems

We define a mechanical analog to the electrical basic circuit element M = dϕ/dQ, namely the ideal mechanical memristance M = dp/dx; p is momentum. We then introduce a mechanical memory resistor which has M(x) independent of velocity v, so it is a perfect (= not-just-memristive) memristor, although its memristance does not crucially involve inert mass. It is practically realizable with a 1cm radius hollow sphere in heavy fuel oil with a temperature gradient. It has a pinched hysteretic loop that collapses at high frequency in the v versus p plot. The mechanical system clarifies the nature of memristor devices that can be hypothesized on grounds of physical symmetries. We hypothesize a missing mechanical perfect memristor, which must be crucially mass-involving (MI) precisely like the 1971 implied EM memristor device needs magnetism. We also construct MI memristive nano systems, which clarifies why perfect MI memristors and EM memristors are still missing and likely impossible.

physics.gen-ph↗

arXiv2014

Against Absolute Actualization: Three "Non-Localities" and Failure of Model-External Randomness made easy with Many-Worlds Models including Stronger Bell-Violation and Correct QM Probability

Experimental violation of Bell-inequalities proves actualization of many futures (~ many-worlds); I show that this is not mere interpretation. To show this self-contained pedagogically, I resolve the EPR paradox by starting with a visually intuitive non-quantum many-worlds model that already has apparent non-locality. A modification leads to a classical-to-quantum transition model. Model-external randomness (a ghost outside the universe throwing a pebble on state-space) stays unchanged, but the modeled observers witness strong Bell-violation. I derive the quantum probability P from classical-to-quantum consistency. Model-internal probability (~ subjective Bayesianism) is derived as a measure of surprise (~ Deutsch's rational expectation). The model shows how absolute actualization, say by real hidden variables, fails. Models with P and standard Bell-violation are supplied for completeness. The transition model is the first touchable, interactive science-outreach exhibit teaching correct quantum physics. The discussion reinterprets the transition model, defends Einstein-locality, rejects "realism" etc., to the conclusion that the models teach the necessity of "many worlds/minds", rejecting probability concepts with random-randomness regress. The models teach how EPR empirically excludes certain realisms.

quant-ph↗

arXiv2013

Exploring Inequality Violations by Classical Hidden Variables Numerically

There are increasingly suggestions for computer simulations of quantum statistics which try to violate Bell type inequalities via classical, common cause correlations. The Clauser-Horne-Shimony-Holt (CHSH) inequality is very robust. However, we argue that with the Einstein-Podolsky-Rosen setup, the CHSH is inferior to the Bell inequality, although and because the latter must assume anti-correlation of entangled photon singlet states. We simulate how often quantum behavior violates both inequalities, depending on the number of photons. Violating Bell 99% of the time is argued to be an ideal benchmark. We present hidden variables that violate the Bell and CHSH inequalities with 50% probability, and ones which violate Bell 85% of the time when missing 13% anti-correlation. We discuss how to present the quantum correlations to a wide audience and conclude that, when defending against claims of hidden classicality, one should demand numerical simulations and insist on anti-correlation and the full amount of Bell violation. This preprint version adds a section on realisms and shows the actual programs with output.

quant-ph↗

arXiv2013

Historical Parallels between, and Modal Realism underlying Einstein and Everett Relativities

A century ago, "past" and "future", previously strictly apart, mixed up and merged. Temporal terminology improved. Today, not actualized quantum states, that is merely "possible" alternatives, objectively "exist" (are real) when they interfere. Again, two previously strictly immiscible realms mix. Now, modal terminology is insufficient. Both times, extreme reactions reach from rejection of the empirical science to mystic holism. This paper shows how progress started with the relativization of previously absolute terms, first through Einstein's relativity and now through Everett's relative state description, which is a modal realism. The historical parallels suggest mere relativization is insufficient. A deformation of domains occurs: The determined past and the dependent future were restricted to smaller regions of space-time. This light cone description is superior to hyperspace foliations and already entails the modal realism of quantum mechanics. Moreover, an entirely new region, namely the "absolute elsewhere" was identified. The historical precedent suggests that modal terminology may need a similar extension. Discussing the modal realistic connection underlying both relativities, Popper's proof of future indeterminism is turned to shatter the past already into many worlds/minds, thus Everett relativity is merely the Bell inequality violating correlation between possible empirical records.

physics.hist-ph↗

arXiv2012

Quantum Randi Challenge

Observed violations of Bell type inequalities exclude all relativistic micro causal ("local"), counterfactual definite ("real") hidden variable models of nature. This further relativization of our concept of reality triggers a growing pseudoscientific resistance against quantum mechanics (QM). I define Didactic Randi Challenges (DRC) via five characteristics. These are challenges which, according to the laws of nature, are impossible to meet. They effectively refute pseudoscientific claims according to which the challenge could easily be met. DRC work by being known to exist while never having been overcome, despite the large rewards which would follow from meeting the challenge. Pseudoscience exploits well meaning engagement in argument to create the appearance of an expert dispute (sowing doubt). DRC decline to discuss "until the challenge is met", without solidifying the perception of establishment conspiracy. This requires transparency, thus DRC are efficient didactic tools. The Quantum Randi Challenge (QRC) is a DRC designed to reject hidden variable models by simply teaching QM; there is no bet or interaction with challengers. The QRC is a computer game that anybody can modify. The present version includes a simulation of true QM behavior that violates Bell 99% of the time, hidden variables that violate the Bell and CHSH inequality with 50% probability, and ones which violate Bell 85% of the time when missing 13% anti-correlation. The DRC challenge is to modify the hidden variables so that the predicted QM behavior arises, including anti-correlation. If such were possible, the presented programs would make it trivial to meet the challenge. This fact and the whole QRC can be taught to a wide audience via the presented heuristics. Demanding anti-correlation is argued to be superior to employing CHSH.

physics.hist-ph↗

arXiv2012

The Missing Memristor: Novel Nanotechnology or rather new Case Study for the Philosophy and Sociology of Science?

In 2008, it was widely announced that the missing memristor, a basic two-terminal electrical circuit element, had finally been discovered. The memristor is the fourth and last such circuit element and thus completes circuit theory. Predicted already in 1971, the eventual discovery of something seemingly so basic needed almost 40 years. However, this discovery is doubted. The predicted memristor has no material memory and is based on magnetic flux, but the discovered devices constitute analogue memory storage that do not involve magnetism. The person who originally proposed the memristor did not reject the discovery but instead changed his mind about what a memristor is. We briefly introduce the history and then carefully memristance and the memristor as such. We discuss its status as a model rather than a device. We discuss the discovered devices, their stability, and how stability relates to the consistency of the theoretical entities. A thought experiment assumes a world without magnetism. Inductors cannot exist there, but memory resistors could still be constructed. On the same grounds as the memristor was historically predicted, an "inductor" could then be predicted. Likely, somebody would also 'discover' one. A tentative sociological analysis compares to the flawed detection of gravitational waves but comes to very different conclusions.

physics.gen-ph↗

arXiv2011

Supporting Abstract Relational Space-Time as Fundamental without Doctrinism against Emergence

Modern physics, via the standard model with Higgs mechanism and string theory for example, has supplied ether-like models and emergent general relativity scenarios that substantially weaken the usual defense of orthodox relativity and abstract, relational space-time in general. Over a dozen arguments in support of relativism against space-substances are discussed. It is not known whether perceived space-time is fundamental or due to a condensed state or string theoretical membrane. Emergent relativity indicates perhaps a whole tower of more fundamental space-times. Whether space is best described as a thing, an emergent phenomenon, or instead Kant's necessary, a priori pre-condition of the possibility of all phenomena, depends on which space-time is under consideration. Nevertheless, space-time is fundamentally abstract relational. This is supported by throughout acknowledging as well as illustrating the value of space-substance models, yet still keeping firm in refusing them on the deepest level. The gist is that even while refusing, physics and philosophy gain more from ether concepts than from plainly refusing them.

physics.hist-ph↗

arXiv2011

Many Worlds Model resolving the Einstein Podolsky Rosen paradox via a Direct Realism to Modal Realism Transition that preserves Einstein Locality

The violation of Bell inequalities by quantum physical experiments disproves all relativistic micro causal, classically real models, short Local Realistic Models (LRM). Non-locality, the infamous "spooky interaction at a distance" (A. Einstein), is already sufficiently 'unreal' to motivate modifying the "realistic" in "local realistic". This has led to many worlds and finally many minds interpretations. We introduce a simple many world model that resolves the Einstein Podolsky Rosen paradox. The model starts out as a classical LRM, thus clarifying that the many worlds concept alone does not imply quantum physics. Some of the desired non-locality, e.g. anti-correlation at equal measurement angles, is already present, but Bell's inequality can of course not be violated. A single and natural step turns this LRM into a quantum model predicting the correct probabilities. Intriguingly, the crucial step does obviously not modify locality but instead reality: What before could have still been a direct realism turns into modal realism. This supports the trend away from the focus on non-locality in quantum mechanics towards a mature structural realism that preserves micro causality.

quant-ph↗

arXiv2010

On the apparently fixed dispersion of size distributions

Probability density functions (PDF) of statistical distributions of cluster sizes N, where N is the number of particles in the cluster, often seem to have less freedom than expected from considering the number of degrees of freedom at the clusters' source. The full width at half maximum appears to be comparable to the average . Such a hidden symmetry is intriguing theoretically and practically impairs size selection towards narrow distributions. However, reviewing the example of Helium cluster beams demonstrates that the origin of the apparent fixing is the assumption that the distributions should be log-normal or exponential and the subsequent use of these functions to fit the data in n = ln(N) log-space. This demands more care when using parametric statistics. Alternatives to the traditionally employed fitting functions are discussed.

physics.data-an↗

arXiv2010

Metric Expansion from Microscopic Dynamics in an Inhomogeneous Universe

Theories with ingredients like the Higgs mechanism, gravitons, and inflaton fields rejuvenate the idea that relativistic kinematics is dynamically emergent. Eternal inflation treats the Hubble constant H as depending on location. Microscopic dynamics implies that H is over much smaller lengths than pocket universes to be understood as a local space reproduction rate. We illustrate this via discussing that even exponential inflation in TeV-gravity is slow on the relevant time scale. In our on small scales inhomogeneous cosmos, a reproduction rate H depends on position. We therefore discuss Einstein-Straus vacuoles and a Lindquist-Wheeler like lattice to connect the local rate properly with the scaling of an expanding cosmos. Consistency allows H to locally depend on Weyl curvature similar to vacuum polarization. We derive a proportionality constant known from Kepler's third law and discuss the implications for the finiteness of the cosmological constant.

gr-qc↗

arXiv2010

Helium Clusters Capture of Heliophobes, Strong Depletion and Spin dependent Pick-up Statistics

This much revised and shortened PhD thesis contains many ideas that I could not follow up on, like self destructing beams in scattering cells, the depletion enhancing Wittig tube, ionic seeding via beta-decay foil or Langmuir-Taylor filaments, analysis of the popular ~ Delta(N) relation in droplet size distributions, etc. Avoiding pasting again the usual that is found in many a thesis in the He-droplet field, we focus instead on what is presented insufficiently rigorous elsewhere, like chopper selection, ionization yield curves, or certain widely employed yet wrong derivations. It is not telling much about successes (e.g. first observation of alkali clusters A_k on He_N with k > 3, proof of their surface location, prediction of constant signal ratios via spin statistics) but goes mainly into the failures, as these are more interesting to those who like to explore truly new territory. Some ideas here may just need a single good insight of yours to turn them into success.

physics.chem-ph↗

arXiv2009

Collision statistics of clusters: From Poisson model to Poisson mixtures

Clusters traverse a gas and collide with gas particles. The gas particles are adsorbed and the clusters become hosts. If the clusters are size selected, the number of guests will be Poisson distributed. We review this by showcasing four laboratory procedures that all rely on the validity of the Poisson model. The effects of a statistical distribution of the cluster sizes in a beam of clusters are discussed. We derive the average collision rates. Additionally, we present Poisson mixture models that involve also standard deviations. We derive the collision statistics for common size distributions of hosts and also for some generalizations thereof. The models can be applied to large noble gas clusters traversing doping gas. While outlining how to fit a generalized Poisson to the statistics, we still find even these Poisson models to be often insufficient.

physics.chem-ph↗

arXiv2002

Work functions, ionization potentials, and in-between: Scaling relations based on the image charge model

We revisit a model in which the ionization energy of a metal particle is associated with the work done by the image charge force in moving the electron from infinity to a small cut-off distance just outside the surface. We show that this model can be compactly, and productively, employed to study the size dependence of electron removal energies over the range encompassing bulk surfaces, finite clusters, and individual atoms. It accounts in a straightforward manner for the empirically known correlation between the atomic ionization potential (IP) and the metal work function (WF), IP/WF$\sim$2. We formulate simple expressions for the model parameters, requiring only a single property (the atomic polarizability or the nearest neighbor distance) as input. Without any additional adjustable parameters, the model yields both the IP and the WF within $\sim$10% for all metallic elements, as well as matches the size evolution of the ionization potentials of finite metal clusters for a large fraction of the experimental data. The parametrization takes advantage of a remarkably constant numerical correlation between the nearest-neighbor distance in a crystal, the cube root of the atomic polarizability, and the image force cutoff length. The paper also includes an analytical derivation of the relation of the outer radius of a cluster of close-packed spheres to its geometric structure.

physics.atm-clus↗

arXiv1999

Examples of Black Holes in Two-Time Physics

Two time theory is derived via localization of the global Sp(2) [or Osp(1/2), Osp(N/2), Sp(2N),...] symmetry in phase space in order to give a self contained introduction to two time theory. Then it is shown that from the two-times physics point of view theories of point particles on many known black hole backgrounds are Sp(2) gauge duals of one another and of course also gauge dual to all other equal dimensional gauges from earlier two time related publications (hydrogen atom, ...). We reproduce the free (quantum) relativistic particle on 1+1 dimensional black hole backgrounds and 2+1 dimensional BTZ ones. Other 2+1 black holes and n+1 ones are touched on but explicitely found only as cross sections of complicated (n+1)+1 backgrounds. Further we give near horizon solutions (e.g. n+1 Robertson-Bertotti). Since two time physics can reproduce these backgrounds all particle actions have hidden symmetries that have not been noticed before.

hep-th↗

arXiv1999

Nature: "I have Two Times"

This is a slightly extended version of a seminar given the 8th of June at the TASI 99 at Colorado University in Boulder. The motivations behind two time theory are explained and the theory is introduced via one of the theory's easier gauges of a particle on a black hole background. Important results that should be interesting as well in the light of the recent AdS mania will be summarized.

hep-th↗

arXiv1997

Black Hole Thermodynamics in Semi-Classical and Superstring Theory

This is a revised and shortened version of a MSc thesis submitted to the University of Sussex, UK. An introduction into the pre-string physics of black holes and related thermodynamics is given. Then, starting with an introduction of how superstring theory is approaching the problem of black hole entropy, work on that and closely related topics like Hawking radiation and the information paradox is reviewed.

hep-th↗