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1. ### I Formula for the propagation of complex errors

I got stuck, not able to get the result. Can someone show me how to do it please?
2. ### I Formula for the propagation of complex errors

Can you give me an example. Suppose the function is: ##f(x, y) = x + y^2## In the non-complex case, with the data given in the previous post, I would proceed as follows: ##f(x, y) = x + y^2 = (3+(-2)^2) \pm \sqrt{0.1^2+(2*(-2) *0.1)^2}= 7\pm \sqrt{0.01+0.16}=7\pm0.41## How can I change to polar...
3. ### I Formula for the propagation of complex errors

If I have 2 measurements ##x = (3.0 ± 0.1), y = (-2.0 ± 0.1)## and want to calculate how the error propagates when calculating a function from those values this formula should be used: ##f(x, y) = f(x, y) ± \sqrt {(\frac{\partial f}{\partial x}*\Delta x)^2+(\frac{\partial f}{\partial y}*\Delta...
4. ### B Questions about climate and physics

Thank you, that was what I was looking for. So there are events attributable to climate change under some circumstances and others not. Much depends on models, observations, physical understanding of weather phenomena, etc. Your link answers questions 2 and 3. Does anyone have any links that...
5. ### B Questions about climate and physics

The fact that rising temperature may cause in increase of extreme phenomena is likely, but is it true? The increase in many of the phenomena (both in intensity and frequency) that climatologists talk about are simply not true. There is no increase in hurricanes, nor tornadoes, nor floods, nor...
6. ### B Questions about climate and physics

1)The atmosphere is an extremely complex system, so much so that weather forecasts beyond a few days are not possible. Why are seasonal or 10-20 year climatological forecasts reliable? I heard from a climatologist in a video on YB (I know it is not a valid source) that weather forecasts are an...
7. ### Neural networks as mathematical models of intelligence

Many people argue that we do not know how the brain works and therefore we can never reproduce a program that shows intelligence, however, this argument is just illogical. First of all, because you don't need to know how something works to reproduce it, moreover, the human brain is a specific...
8. ### Neural networks as mathematical models of intelligence

Why do almost all people not think that neural networks are the mathematical model of intelligence? I briefly explain what I understand: -A neuron is a mathematical object that takes numerical inputs from other nearby neurons, applies a nonlinear function (combining the input with numbers...
9. ### How much statistical mechanics is enough for a physicist?

I think the links you recommended are too advanced for me. I am starting to study QFT, but I am also interested in astrophysics, cosmology, and black holes. In general, I am interested in a statistical mechanics book that will allow me to understand graduate level physics. My current level is...
10. ### How much statistical mechanics is enough for a physicist?

I just finished studying Berkeley Statistical Physics by Reif. Some things I already knew, from Tong's notes. What should I study to get on with statistical mechanics at an appropriate level in your opinion? I saw that there are various statistical mechanics textbooks, what do you recommend and...
11. ### I Repeated measurements on a quantum system interacting with other quantum systems

In quantum mechanics if I repeat a measurement of the same observable in succession I get the same quantum state if it is not a degenerate state. If I make the system under consideration interact with another quantum system and meanwhile keep measuring it what happens? Does the system not...
12. ### A Schrodinger equation in quantum field theory

Thanks to everyone
13. ### A Schrodinger equation in quantum field theory

That sentence is wrong, sorry, I meant to say I read online (a question on stackexchange) that quantum mechanics is related to scalar QFT in 0+1 dimensions. I would like to know more about it.
14. ### A Schrodinger equation in quantum field theory

What is the Schrodinger equation in QFT? is it the nonrelativistic approximation of a Klein-Gordon scalar field? or Is there more? I have read that the Schrodinger equation describes a QFT in 0 dimensions. I accept every answer
15. ### I Exploring the Big Picture of QFT

References, links, notes, textbooks, papers, videos, etc. are welcome. Vanadium 50 Excuse me if my questions are naive. If this or other threads started by me are inappropriate, feel free to delete them. If you think I am contributing negatively on this site feel free to delete my account.
16. ### I Exploring the Big Picture of QFT

By big picture I mean: -the things that are there -the relationships between things -the fundamental mathematical topics (e.g. what group theory is for in QFT) -what are the typical applications and problems -how you would describe QFT in a nutshell Your interpretations of "big picture" are also...
17. ### How much statistical mechanics is enough for a physicist?

How much statistical mechanics do I need to know to study QFT, astrophysics, black hole thermodynamics, and other advanced topics? And where should I study it in your opinion? So far I have only read Tong's notes however I don't think it is enough. Some quantum statistical mechanics is also...
18. ### I Exploring the Big Picture of QFT

What is the big picture of QFT? I have studied quantum mechanics from: -Griffiths -the first few chapters of Sakurai -Ballentine I have studied electrodynamics from Griffiths and General Relativity from Carroll I have assigned level I to the question, but any answer is welcome
19. ### I What does the output of a radio telescope look like?

What does the output of a radio telescope look like? I suppose it is not an image like that of a telescope observing visible light
20. ### I Measuring the rotation curve of galaxies

What should I learn to make astrophysical measurements from open data? Suppose I want to measure the rotation speed of galaxies to generate galactic rotation curves like these: https://en.wikipedia.org/wiki/Galaxy_rotation_curve What should I do and what should I learn? I think I should get...
21. ### A MOND: Two Small Masses at Great Distance - Orbit Speed

All answers from all levels are welcome
22. ### A MOND: Two Small Masses at Great Distance - Orbit Speed

In MOND should two small masses placed at a great distance orbit faster than in Newtonian dynamics? Would it be theoretically possible to do this experiment in the solar system, or would the presence of the sun and earth be a problem?
23. ### References for studying MOND

Can you recommend papers and books to study MOND? I know that a lot of MOND theories have been ruled out by recent observations, so I don't know where to start without wasting time studying from outdated references. I know GR from Carroll's book and cosmology from "Physical Foundations Of...
24. ### I Analysis of data from previous experiments

Has it ever happened that after a discovery, data from previous experiments were analyzed and it was noticed that there was already some evidence of the phenomenon in question?
25. ### I Does this tweet have any physical interpretation?

I read this tweet (I omit the author for privacy), and my curiosity led me to ask questions:: Any optimization problem is equivalent to a convex (linear) one (but infinite dimensional…). The key do perform global optimization using Lasserre’s relaxation via the problem of moment (aka...
26. ### B Color of a mirror on the Earth

There are many solar power plants using large mirrors on earth. Their color as seen from the satellite is blue. (source google maps: planta solar 10 Spain) I have another question: if I have a photo of the sky taken with a smartphone, can I get physically meaningful data from the colors in the...
27. ### B Color of a mirror on the Earth

Aren't the colors in this photo mainly due to the color of things? In a mirror, the color observed should be almost only that of the light scattered by the atmosphere.
28. ### B Color of a mirror on the Earth

No. If I look at the mirror from a given angle I see: the light scattered by the air between me and the mirror and the light scattered by the air placed symmetrically on the opposite side. The light scattered by the latter has to go a long way before it reaches the observer who is outside the...
29. ### B Color of a mirror on the Earth

Because if I stand outside the atmosphere, the reflected light has to travel a lot farther, but I don't know if that is enough to make the reflection in the mirror turn red. I expect that depending on the angle it should change the reflected color.
30. ### B Color of a mirror on the Earth

During the night, black. During the day, I don't know whether blue or red.
31. ### B Color of a mirror on the Earth

If I place a mirror on the ground facing upward, what color will those who observe it from space see?
32. ### How useful is a symbolic calculation tool?

How often during your work do you use a symbolic calculation tool like Mathematica / Maple / SymPy? Is it worth learning(especially for a theoretical physicist)? Thank you.
33. ### MATLAB No End" Boundary Conditions in Wave on a String

Thank you. How do I eliminate the waves traveling to the left if I am simulating the wave equation with a simple finite difference method?
34. ### MATLAB No End" Boundary Conditions in Wave on a String

How did they impose boundary conditions here if "no end" is selected? Here: https://phet.colorado.edu/sims/html/wave-on-a-string/latest/wave-on-a-string_en.html I would like to do the same thing without changing the wave equation of the string.
35. ### MATLAB Boundary conditions in the resolution of a PDE with the FFT method

How to impose boundary conditions when solving a PDE with fft? For example here: If I copy this code I get periodic boundary conditions. Thank you
36. ### B What is the underlying phenomenon of waves?

Astronuc. The simplest wave equation is enough for me.
37. ### I Bullet cluster and dark matter

I found this: https://arxiv.org/pdf/1003.0939.pdf
38. ### B What is the underlying phenomenon of waves?

What I mean is: is it possible to do something like this: "" -min 3- with waves?
39. ### I Bullet cluster and dark matter

Is the bullet cluster evidence for or against dark matter? I understand the explanation that it is evidence in favor of the existence of dark matter, and it convinces me. However, some argue that it is evidence against its existence? Why?
40. ### B What is the underlying phenomenon of waves?

pinball1970 Sorry, maybe I misunderstood your message because I am using a translator. Do you have an advanced level explanation? If yes please write it down, I will try to understand. Thank you.
41. ### B What is the underlying phenomenon of waves?

I changed the level to B, so I can understand
42. ### B What is the underlying phenomenon of waves?

Heat diffusion is caused by randomly moving particles. So there is a connection between the diffusion equation and the statistical motion of particles. Is there something similar for waves?
43. ### I What are the limits of particle accelerators?

What prevents making a particle accelerator better than the LHC but only a few centimeters big? After all, you accelerate objects with very small masses. Are there insuperable physical limits? What are the physical limitations?
44. ### I What happens to the other particle in an entanglement state?

I understood that measurement is a physically vague concept (although mathematically defined as the collapse of the wave function), it happens when a particle hits an instrument, i.e., a macroscopic object. is that right? Now, if we have two particles in an entagled state and I measure one...
45. ### I Entanglement in NRQM and QFT

If I wait long enough can two or more particles in distant galaxies end up in an entangled state?
46. ### I What happens to the other particle in an entanglement state?

if I have two particles in an entangled state, I make them travel in different directions, and I measure the state of only one of them then I know the outcome of the measurement of the other. But when I take a measurement on the first particle, what happens to the second? Does it undergo a...
47. ### I Why Is Minkowski Spacetime Non-Euclidean?

Isn't the fact that the spacetime metric is not Euclidean due to the fact that there is a maximum velocity in our universe? maximum velocity ##\implies## everyone agrees on its value ##\implies## derivation of spacetime interval (##ds^2=-dt^2+dx^2+dy^2+dz^2##) Is this reasoning wrong? Doesn't...
48. ### Looking for an up-to-date cosmology textbook

I know I should not study cosmology from books that are too dated. Can you recommend an up-to-date cosmology book? I am studying GR from Carroll's book. Do I need to study astrophysics first or other topics?
49. ### I Entanglement in NRQM and QFT

Can entangled states be generated only locally? For example if I have a particle that decays I know entangled particles can be generated. Or can entangled states be generated even between distant particles? For example if I have one particle here and one on a distant galaxy, if I wait long...
50. ### I The quantum state of the Universe

If entagnled is any state that cannot be expressed as the product of the states of the individual particles that compose it, then yes. I used the word "weird" because I don't know if either the word entangled is valid for describing states of physically distant particles.