The Stack Overflow podcast is back! Listen to an interview with our new CEO.

Questions tagged [foundations]

Devoted to the conceptual bases of the fundamental theories of physics, to their philosophical and logical premises.

Filter by
Sorted by
Tagged with
3
votes
1answer
49 views

Theories, Corollaries, and Models

I apologize if this question seems overly basic. I was wondering how to recognize what a theory is really saying, as opposed to the explanation/corollaries that are drawn from it. As an example, take ...
3
votes
0answers
173 views

Modern axioms of quantum mechanics

Recently I have been learning a lot about what kind of axioms and mathematical formulations there are for non-relativistic quantum mechanics. Unfortunately, I am a little confused, because at first I ...
2
votes
1answer
215 views

Are certain fields of physics axiomatized?

Everything from Quantum mechanics can be derived from six (?) postulates. Similarly classical electrodynamics can be reduced to Maxwell's equations and Lorentz force law, and special relativity is ...
2
votes
2answers
238 views

How rigorous can conservation of energy be made?

The principle conservation of energy is often taken as an obvious fact, or law of nature. But it seems to me the definition of energy is far from obvious, or natural: http://en.wikipedia.org/wiki/...
2
votes
3answers
2k views

Can a theory be proven by an experiment (or series of) that sustains it?

This is a question that I've always had but it wasn't until the recent news regarding the BICEP2 experiment that I really gave thought about it (please note that the question is general and not ...
2
votes
3answers
164 views

Contravariant metric in Newton-Cartan spacetime

I'm interested in the geometrized Newtonian gravitation or Newton-Cartan theory. In every reference that I have found begins saying that a Newton-Cartan spacetime is a manifold $M$ with some ...
2
votes
1answer
90 views

What is “fundamental” in physics?

Sorry about the broad question. I'm still learning to frame the questions on Physics StackExchange. Currently researching the nature of interactions in philosophy. My question is: When physicists ...
2
votes
1answer
73 views

How much freedom is there in a quantum field?

Let's imagine we have a free scalar quantum field, and that it has 2 particles in a specific momentum eigenstate only. Does this information completely fix the quantum field, or is there additional ...
2
votes
2answers
165 views

The principles of statics without force

I'm a student of civil engineering and now my course is covering the basics of statics, such as the equations of equilibrium, etc. Trying to get a better basis on the subject, I started to search on ...
2
votes
2answers
2k views

The meaning of 'postulate' in physics? [duplicate]

What does postulate mean in physics? What is its role in physical theories? Is it possible to break physical postulates?
2
votes
1answer
29 views

If the only two empirical measurements we can make are change in length and passage of time, how are dimensions and units of quantities formulated?

So this is something really confusing to me. Recently a professor of mine gave a talk and said something that I thought was very interesting and kind of crazy. "The only two quantitative measurements ...
2
votes
0answers
87 views

What “determines” a specific quantum theory

I'm trying to give a bare bones description of non-relativistic quantum mechanics, for mathematicians. A description of the mathematical machinery. It is meant to answer to the questions: What makes ...
2
votes
0answers
89 views

Is there an official list of the postulates of quantum mechanics?

Having been looking at lecture notes, online sources and books, the list of postulates of quantum mechanics seems to vary. For instance, some sources (my lecture notes, for instance) refer to $|\...
2
votes
0answers
39 views

Spekken toy model: measurement of spin in any direction

Spekkens' toy model [1] can handle the measurement of a spin 1/2 along the directions $x$, $y$ and $z$. Unless I am missing something, it can't handle measurement in any direction. Would there be a ...
2
votes
0answers
214 views

The implications of Gödel's Second Incompleteness Theorem on Theoretical Physics models [duplicate]

Does Gödel's Second Incompleteness Theorem imply that no Theoretical Physics model of reality can be proved to be consistent using the laws of physics? I work partially in Quantum Information Theory ...
2
votes
0answers
233 views

Only gravitation and Newton's $2^{\mathrm{nd}}$ law needed to derive Kepler's laws?

It is known that Kepler's laws of planetary motion can be derived from Newton's laws of motion and his law of universal gravitation. However, are all of Newton's laws of motion necessary? According ...
1
vote
2answers
293 views

What are the practical applications of quantum foundations?

Many quantum foundation researchers keep emphasizing that For All Practical Purposes (FAPP), quantum foundations are irrelevant. They even invented an acronym for it! Does that mean that quantum ...
1
vote
3answers
176 views

Encoding infinite information in a qubit vs. classical system

In this Quantum Computing article by Michael Nielsen he argues about some of the limitations imposed by quantum measurement. In particular how the amplitude $\alpha$ of a single qubit $\alpha |0> +...
1
vote
1answer
63 views

Statistical error with large number of particles in weak measurements

Consider a measurement process. If $\Delta \pi$ and $\Delta x_n$ is the uncertainty in momentum and position of the measuring device. Aharonov, Albert, et al. ask us to consider the opposite limit: ...
1
vote
3answers
353 views

What Statistical Mechanics does in classical regime

In a book of Dipankar Home, "Foundations of Quantum Mechanics", he has mentioned that A newer theory should not only predict all the results that are already predicted by it's predecessor where it ...
1
vote
3answers
618 views

Is the classical world an illusion?

In the paper Zeh, H. D. The Wave Function: It or Bit? In Science and Ultimate Reality, eds. J.D. Barrow, P.C.W. Davies, and C.L. Harper Jr. (Cambridge University Press, 2004), pp. 103-120. arXiv:...
1
vote
1answer
84 views

Is photon interference really random? [closed]

I know that according to the many worlds interpretation, there is no randomness and rather there is a universal wave function that simulates an observer with a continuously branching timeline. My ...
1
vote
1answer
166 views

About Hilbert and Physics [duplicate]

Was one of Hilbert questions regarding physics to make an axiomatic foundation for physics? Regardless of Godels work could some Physics principles that are 'basic' and 'presently verifiable' be ...
1
vote
1answer
300 views

All of the postulates of quantum mechanics without additional information [closed]

$\newcommand{\braket}[2]{\left<#1|#2\right>}% \newcommand{\bra}[1]{\left<#1\right|}% \newcommand{\ket}[1]{\left|#1\right>}% $As an undergraduate who's trying to learn quantum mechanics it'...
1
vote
2answers
192 views

Relativistic probability amplitude of a particle to be in certain position

In the book “The story of spin” by Tomonaga on page 110, it says They insisted that a concept like "the probability of a particle to be at $x$ in space" is meaningless for relativistic particles—be ...
1
vote
2answers
277 views

Is there any physical meaning for the inverse metric?

I've been wondering if we can attribute any physical meaning to the inverse metric. I mean when we talk about the metric itself, there are lots of insights we can have towards its role in spacetime, ...
1
vote
1answer
353 views

Questions about MTW's “thousand” tests of the Einstein principle

In Misner, Thorne, Wheeler (henceforth written as "MTW"), "Gravitation", Box 16.4, there's an experimental setup construction (or method) presented by which "Each geodesic clock is constructed and ...
1
vote
2answers
100 views

How are propositions concerning spacetime curvature constructed explicitly in terms of coincidences?

Is Einstein's insight [1] that All our well-substantiated space-time propositions amount to the determination of space-time coincidences [such as] encounters between two or more [...] material ...
1
vote
0answers
28 views

What is the role of metric transitivity in statistical mechanics?

I was reading a paper of E.T. Jaynes 'Information Theory and Statistical Mechanics'. There he mentions the following principle in the section 'Application to Statistical Mechanics': The link to paper ...
1
vote
0answers
200 views

Local determinism vs. Local realism vs. Local causality

I found the following definitions for the three different terms. Do you find these definitions exhaustive, or can you suggest more precise formulations? Quoting the wikipedia page on Local realism: ...
1
vote
1answer
61 views

What is the difference between no-disturbance principle and non-contextuality?

The no-disturbance (ND) principle states that, for any three observables A, B, and C such that A and B are compatible, and A and C are compatible, the probabilities of outcomes of A do not depend on ...
1
vote
0answers
101 views

Causality in Quantum mechanics

If we consider a quantum preparation procedure on a system followed by a projection measurement as constituting two sequential events in space-time (which seems plausible ,given that the Copenhagen ...
1
vote
0answers
90 views

Interpretation of quantum superposition and classical Brownian motion

In the standard, Copenhagen interpretation of quantum mechanics, the usual ontology assigned to the phenomenon that repeated measurements of a quantum mechanical observable yielding different results ...
1
vote
0answers
193 views

Improvement of Von Neumann's measurement scheme [closed]

I would like to know some references on possible improvements of Von Neumann's measurement scheme beyond the use of POVMs. Specifically, I am interested in the possibility of implementing a sort of ...
1
vote
0answers
83 views

Why not measure the velocity of a quantum particle by $\frac{\Delta \vec{x}}{\Delta t}$

Why is it not possible in quantum mechanics to measure the velocity (and thus momentum) of a particle just by two position and time measurements and get it approximately by $$ \vec{v} = \frac{\vec{x}...
1
vote
1answer
219 views

A Spin up particle in QFT

This appears like a question that is rarely addressed in field theory pedagogy (perhaps because the answer is obvious): how does one describe a particle of definite spin in quantum field theory? For ...
1
vote
0answers
54 views

Ontic state space from operational structures

Operationalism eschews a notion of system state in favour of the empirical behaviours of preparation and measurement. Abramsky has formalized operational structures as Chu spaces. It would be nice ...
1
vote
0answers
158 views

Can quantum field theory be seen as an epistemic restriction on (quantum) causal structure

Suppose we take Vicary's quantum harmonic oscilator as a kind of "toy quantum field theory". Next, take the category of internal comonoids to not represent the background causal structure. We ...
1
vote
0answers
30 views

Does it make sense to speak of amplitudes of finite closed boundaries in QFT?

A example of amplitude in Relativistic Quantum Mechanics or specifically in QFT is the amplitude of a field configuration on a space-like hyper-surface of space-time to "lead" to another field ...
0
votes
2answers
292 views

Is Bells inequality always violated? [closed]

Is Bell inequality always violated by a quantum system? Can it ever be violated by a classical system?
0
votes
3answers
235 views

What is the program of quantum field theory? What is its derivation?

Paraphrasing Griffith's: For some particle of mass m constrained to the x-axis subject to some force $F(x,t)=-∂V/∂x$, the program of classical mechanics is to determine the particle's position at any ...
0
votes
2answers
164 views

Is the one-dimensional string actually a real string, with some diameter to its cross section — just as a rope has some thickness?

Would not a one-dimensional string be just a Platonic idea, and not actually physical? Because if physical, the one dimensional string would comprise a line of point particles, each point particle ...
0
votes
1answer
90 views

Defining Quantum Mechanics

Does Schrödinger's Equation (Operator form) $[\hat{X},\hat{P}]=i$ Born Rules define Quantum Mechanics?
0
votes
1answer
556 views

Why should we believe in clock hypothesis? [closed]

It is often assumed in special relativity that the rate of a clock in a non inertial frame does not depend on the proper acceleration of the observer. The point is, Rindler's observer shows us that ...
0
votes
1answer
44 views

Quantum state space constructing operator

If I use British money the amounts I can have are isomorphic to $\mathbb{Z}_{\geq0}$ (in pennies). If I also use Australian money, if I want to think about the amount I have in total, I can use ...
0
votes
1answer
117 views

Non-negotiable laws in physics [closed]

Are there laws (axioms / principles / equations / inequalities) in physics that cannot be violated, no matter how slightly, by hand without leading to absurdities (singularities, inconsistencies)?
0
votes
2answers
60 views

How non-conservative fields emerged in the universe?

I know all of the fundamental forces/fields(Gravitational, Electromagnetic, Strong and Weak) of the nature are conservative and we know every other derived force/field in the nature is just produced ...
0
votes
2answers
277 views

Tensor product postulate [duplicate]

Non relativistic quantum mechanics assumes that a composite system should be described with the tensor product of the component systems. This is the tensor product postulate of quantum mechanics. I ...
0
votes
2answers
257 views

Postulates of Relativistic Quantum Mechanics

I have been reading this Phys.SE answer in order to clarify my doubts. It seems to me that he claims that the postulates are the same no matter if it is QFT, QM or whatever. But some books tell us ...
0
votes
2answers
96 views

Proving the orthogonaity property by using using the reality condition

I am reading Modern Quantum Mechanics by Sakuria and Napolitano. Background Information from the Textbook a' and a'' are eigenvalues of A. A is a Hermitian operator. The symbol, * , implies ...