The foundations tag has no wiki summary.
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5answers
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General relativity and the microscopic/macroscopic distinction
Here is Wikipedia's diagram of the stress-energy tensor in general relativity:
I notice that all of its elements are what would be termed "macroscopic" quantities in thermodynamics. That is, in ...
11
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3answers
469 views
The interpretation of mass in quantum field theories
Consider a free theory with one real scalar field:
$$
\mathcal{L}:=-\frac{1}{2}\partial _\mu \phi \partial ^\mu \phi -\frac{1}{2}m^2\phi ^2.
$$
We write this positive coefficient in front of $\phi ^2$ ...
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0answers
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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 ...
15
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11answers
973 views
Why quantum mechanics?
Imagine you're teaching a first course on quantum mechanics in which your students are well-versed in classical mechanics, but have never seen any quantum before. How would you motivate the subject ...
51
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6answers
844 views
What are the justifying foundations of statistical mechanics without appealing to the ergodic hypothesis?
This question was listed as one of the questions in the proposal (see here), and I didn't know the answer. I don't know the ethics on blatantly stealing such a question, so if it should be deleted or ...
13
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6answers
550 views
Is the density operator a mathematical convenience or a 'fundamental' aspect of quantum mechanics?
In quantum mechanics, one makes the distinction between mixed states and pure states. A classic example of a mixed state is a beam of photons in which 50% have spin in the positive $z$-direction and ...
1
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0answers
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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 ...
1
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3answers
383 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. ...
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3answers
160 views
Banach Space representations of physical systems
I think most physicists mostly model physical systems as some kind of Hilbert space.
Hilbert spaces are a strict subset of Banach spaces.
Questions:
Can physical systems really have non-compact ...
11
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3answers
131 views
POVMs that do not require enlargement of the Hilbert space
The usual justification for regarding POVMs as fundamental measurements is via Neumark's theorem, i.e., by showing that they can always be realized by a projective measurement in a larger Hilbert ...
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1answer
91 views
How to go from Quantum World to Classical World? [duplicate]
Possible Duplicate:
Is it possible to recover Classical Mechanics from Schrödinger’s equation?
Classical Limit of the Feynman Path Integral
In the quantum world we don't have ...
0
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0answers
63 views
can we cast physics as an interface to underlying structure? [closed]
I have put down a few thoughts on how we can start to see physics as an interface to underlying "structure". "Structure" is posed without its normal qualifier "Causal" and it will become more clear ...
12
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4answers
566 views
Reason for the discreteness arising in quantum mechanics?
What is the most essential reason that actually leads to the quantization. I am reading the book on quantum mechanics by Griffiths. The quanta in the infinite potential well for e.g. arise due to the ...
0
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0answers
85 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 ...
