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Physics Stack Exchange users whose comments are worth studying include Lubos Motl and Ron Maimon (now at http://www.quora.com/Ron-Maimon and http://www.physicsoverflow.org/user/Ron+Maimon). Also see http://arxiv.org/abs/hep-ph/0207124 for a review of physics since the standard model.


Nov
16
comment Have I discovered how to calculate the proton's mass using only integers?
Fred, the bottom line here is that a kilogram is an arbitrary unit of mass, and if you used a different unit, you would have a different number to explain. The actual numbers in physics that people seek to explain are quantities like "ratio of proton mass to electron mass", which don't depend on units.
Nov
14
comment Is physics rigorous in the mathematical sense?
The ideal of rigor for science is the hypothetico-deductive method. You make a hypothesis, deduce its consequences, and then test them against reality. The mathematical formalization of this process would be something like the AIXI algorithm in computer science, which uses data to make causal models. Also see the whole field of statistics, and its methods for establishing the likelihood of a hypothesis. The difference between mathematics and physics is that in physics you use empirical data as an input. But you can still be rigorous in your methods.
Nov
11
comment Does the Higgs Mechanism contradict Entropic Gravity?
Entropic gravity has other problems arxiv.org/abs/1108.4161 arxiv.org/abs/1108.5240.
Nov
8
awarded  Announcer
Oct
30
comment Reference-request: Computational science and physics
... or exactly how mathematics relates to reality. Galileo's remark is a poetic statement that there is some form of connection but states no details. Unless you adopt the pythagorean position that "reality is mathematics", you need some broader ontological idea in which "number" is just one "aspect" of reality, but that is a nature-of-reality question. It's metaphysics, it's about whether reality consists of "things with properties" or something else entirely.
Oct
30
comment Reference-request: Computational science and physics
UGPhysics, I don't think you know what you're asking. Computability has a specific technical meaning, see "Turing computability". You could hypothetically have a theory of physics that was technically noncomputable, but the only part that could be tested would be a computable truncation of the theory. Insisting that a theory includes an algorithm for making quantitative predictions is just the bare minimum requirement for it to be testable, and doesn't say anything about whether reality contains anything noncomputable in the technical sense, whether reality is "mathematical" ...
Oct
29
comment What does the wind speed have to be to blow away a person?
Sort of similar question: physics.stackexchange.com/q/36439
Oct
28
comment Reference-request: Computational science and physics
But what is the relation between being computable and being mathematical? And why would this be relevant for a TOE, but not for an incomplete theory?
Oct
26
comment Which arguments for $m_u \approx 0$ are still in the market?
arxiv.org/abs/hep-ph/9403203 is the deepest theoretical discussion I have found.
Oct
23
comment Is there perfect vacuum 10000 billion lightyears away?
The second reason is harder to convey, but it has to do with the holographic principle and the existence of a "dual description" of a theory with quantum gravity, on the boundary of its space. The main counterargument here is simply that there is no working example of holographic duality in which the cosmological horizon is the boundary. He's just guessing how the duality works for an expanding universe, and the illogic of the answer suggests he is guessing wrongly.
Oct
23
comment Is there perfect vacuum 10000 billion lightyears away?
mick, Ron is stating a position which fortunately is not yet official dogma among physicists, and will never be, among people who actually study anything galaxy-sized or smaller. He has two motivations. The first is the philosophically extreme position that if you can't measure it, it isn't real. Galaxies in the expanding universe become undetectable once they cross the horizon, so in Ron's philosophy, they no longer exist at that point. No-one who actually studies stars or galaxies is going to believe that they stop existing because we can't see them, of course.
Oct
15
comment Mathematically challenging areas in Quantum information theory and quantum cryptography
"What area in QIT, is the most mathematically challenging and rigorous?" Just ask yourself what is the most challenging and rigorous area in mathematics, and then figure out how to apply it to QIT.
Oct
11
comment Would a spin-2 particle necessarily have to be a graviton?
Other examples are the Vasiliev "higher spin gauge theories".
Oct
4
comment Mathematical probabilistic interepretation of probability amplitude
If you start with the wavefunction $\psi\gamma$, and evolve it according to a Schrodinger equation, the associated probability distribution will develop differently to that obtained by just starting with $\psi$, and evolving it according to the Schrodinger equation. So $\psi$ and $\psi\gamma$ are physically different states. (The only exception is if $\gamma(x)$ is the same for all $x$.) As for why physics works this way, no-one knows.
Oct
4
comment Are the electrons in a quantum hall edge state entangled?
I don't know this subject, but the bulk QH state is a many-electron wavefunction, and in the paper they say there is a current at the edge, so the edge state must be a quantum state describing the evolving charge density at the edge. And I don't see a problem with e.g. the expected charge density at different points on the edge being quantum-correlated.
Oct
3
comment If we had three eyes, would our visual perspective be fourth dimensional?
To get four-dimensional depth perception, you would need two or more eyes that each have a three-dimensional "surface" where the 4D light enters. (And there would need to be four large dimensions for you to see into.)
Oct
1
comment What is relation between Holographic principle and Hologram?
It would be enlightening to have a statement somewhere which does make the analogy between optical holography and gravitational "holography" as precise as possible, but then highlights all the ways in which they are different. That is, you'd talk about the physics of holographic recording and holographic reconstruction, and about the mapping from bulk to boundary and vice versa, and then (somehow!) you'd comment on whether "reference beam" and "reconstruction beam" have any conceptual analogies in AdS/CFT and its relatives.
Sep
24
revised What's the deepest reason why QCD bound states have integer charge?
fix link
Sep
24
revised What's the deepest reason why QCD bound states have integer charge?
link
Sep
24
asked What's the deepest reason why QCD bound states have integer charge?