Biographies, History, Philosophy of Physics

[sbrothy]

I guess a Rasperry PI or similar with a simcard and a foldable (ot laser) keyboard and mouse could do the same.

 

[AlexB23]

I'll look into that. I was thinking on getting a pinephone, bur I thought the "support" was discontinued. No so it seems:

https://pine64.org/devices/pinephone/

That might work, but GrapheneOS is bigger.

 

[sbrothy]

arXiv: Instrumentation and Methods for Astrophysics (astro-ph.IM); History and Philosophy of Physics (physics.hist-ph); Instrumentation and Detectors (physics.ins-det)

The Ohio SETI Program -- The Last Decades

The Ohio State University Radio Observatory (OSURO), known as the Big Ear, played a pivotal role in both radio astronomy and the Search for Extraterrestrial Intelligence (SETI). Following the completion of the Ohio Sky Survey, the facility was repurposed in 1973 as the world's first full-time dedicated SETI observatory and operated continuously until its decommissioning in 1998. During this period, the Ohio SETI Program evolved from an 8-channel hydrogen-line receiver into increasingly sophisticated survey systems. Over three decades, these surveys covered approximately 70% of the radio sky using a largely consistent instrumental configuration, creating one of the most extensive long-term radio astronomy archives ever assembled. The program is best known for the detection of the Wow! Signal in 1977, but it also accumulated an archive of over 40,000 transient narrowband events, revealed unusual concentrations of radio bursts near the Galactic Center, and established one of the longest continuous radio monitoring records in astronomy. Following the closure of the Big Ear, its scientific legacy continued through Project Argus and, more recently, the Arecibo Wow! project. This paper provides an overview of the final decades of the Ohio SETI Program, including its instrumentation, survey strategies, scientific discoveries, and enduring impact on SETI, time-domain radio astronomy, and the preservation of historical astronomical data. Despite its scientific significance, most of the data collected by the Ohio SETI Program remains unexplored, leaving a unique archive available for future research.

EDIT: 70% of the radio sky is pretty impressive!

 

[sbrothy]

arXiv: Mathematical Physics (math-ph); History and Philosophy of Physics (physics.hist-ph):

Why Hadamard states?.

In quantum field theory on curved spacetime, and in locally-covariant quantum field theory, the Hadamard condition is often presented as a necessary condition on 'physically reasonable' states of the quantum field, and plays a central role in many theoretical and foundational applications - ranging from proofs of the renormalizability of Wick polynomials to derivations of the Hawking temperature. Yet despite this, the philosophical and foundational underpinnings of the Hadamard condition remain murky. I critically discuss existing motivations for the Hadamard condition in the literature, before arguing in favour of an alternative justification for the Hadamard condition, according to which it is best understood as a necessary and sufficient condition for the existence of a well-defined operator product on a sufficiently large space of observables of the quantum field, satisfying a variety of further conditions (thus proving a converse to a result which was already discussed in this context). This clarifies the role and status of the Hadamard condition, including its relationship to the equivalence principle, to well-definedness of physical quantities such as Wick polynomials and the expectation value of the stress-energy operator, and the sense in which Hadamard states are 'vacuum-like'.

arXiv: Quantum Physics (quant-ph); History and Philosophy of Physics (physics.hist-ph):

The Physics Behind Symmetrization

It is often asserted that quantum states for same-type particles must be symmetrized due to ``label redundancy,'' i.e. the assumption that the permutations of labels in direct-product states do not reflect any real physical distinction and thus their permutations constitute an ``exchange degeneracy''. This assumption is directly challenged by the case of scattering of same-type particles such as electrons, which involves two physically distinct scattering channels effectively corresponding to permutation of the labels. I discuss this counterexample with critical attention to an extant portrayal in the literature that omits pertinent physical content. I further note ways in which the assumption that symmetrization must be universally imposed is not supported by actual calculations of particle interactions, nor by seemingly viable particle states based on preparations and outcomes.

EDIT: I checked for math this time....

 

[sbrothy]

arXiv: General Physics, History and Philosophy of Physics:

I was fascinated by a discussion about Lorentz's Ether Theory on this site (If nothing else then for historical reasons.) As I have nothing to contribute to the actual discussion I thought I'd put these here for later use:



Albert Einstein and the Fizeau 1851 Water Tube Experiment
The reception of relativity in the Netherlands
Drude's lesser known error of a factor of two and Lorentz's correction


Alice and Bob and Hendrik

This paper offers an alternative approach to discussing both the principle of relativity and the derivation of the Lorentz transformations. This approach uses the idea that there may not be a preferred inertial frame through a privileged access to information about events. In classroom discussions, it has been my experience that this approach produces some lively arguments.

EDIT: I guess it should have been a discussion on, but it's too complicated to change now.

 

[robphy]

Alice and Bob and Hendrik

This arxiv-document is based on Mermin's "Light Rectangles", where the area of causal-diamonds is proportional to the square-interval between opposite corners. It's unfortunate it makes numerous references to Euclidean geometry and uses circular-trigonometry to analyze the figures.
[Mermin does use Euclidean geometry a few times.]
(I'm certain that the arxiv-document can expressed in terms of elapsed times and Doppler-factors and analyzed with hyperbolic-trigonometry...
My "Relativity on Rotated Graph Paper" uses some ideas from Mermin... but I do everything with Minkowski spacetime geometry.)

I think Henrik Lorentz' appearance in this arxiv-document is in the title and in the name of the transformations, but (I think) makes no connection to the LET.

 

[renormalize]

Here's an interesting history of the first 40 or so years of the development of physical cosmology, as told from a Russian perspective: https://arxiv.org/pdf/2607.11791.