A theory is a rational type of abstract thinking about a phenomenon, or the results of such thinking. The process of contemplative and rational thinking is often associated with such processes as observational study or research. Theories may either be scientific or other than scientific (or scientific to less extent). Depending on the context, the results might, for example, include generalized explanations of how nature works. The word has its roots in ancient Greek, but in modern use it has taken on several related meanings.
In modern science, the term "theory" refers to scientific theories, a well-confirmed type of explanation of nature, made in a way consistent with scientific method, and fulfilling the criteria required by modern science. Such theories are described in such a way that scientific tests should be able to provide empirical support for it, or empirical contradiction ("falsify") of it. Scientific theories are the most reliable, rigorous, and comprehensive form of scientific knowledge, in contrast to more common uses of the word "theory" that imply that something is unproven or speculative (which in formal terms is better characterized by the word hypothesis). Scientific theories are distinguished from hypotheses, which are individual empirically testable conjectures, and from scientific laws, which are descriptive accounts of the way nature behaves under certain conditions.
Theories guide the enterprise of finding facts rather than of reaching goals, and are neutral concerning alternatives among values. A theory can be a body of knowledge, which may or may not be associated with particular explanatory models. To theorize is to develop this body of knowledge.The word theory or "in theory" is sometimes used erroneously by people to explain something which they individually did not experience or test before. In those instances, semantically, it is being substituted for another concept, a hypothesis. Instead of using the word "hypothetically", it is replaced by a phrase: "in theory". In some instances the theory's credibility could be contested by calling it "just a theory" (implying that the idea has not even been tested). Hence, that word "theory" is very often contrasted to "practice" (from Greek praxis, πρᾶξις) a Greek term for doing, which is opposed to theory. A "classical example" of the distinction between "theoretical" and "practical" uses the discipline of medicine: medical theory involves trying to understand the causes and nature of health and sickness, while the practical side of medicine is trying to make people healthy. These two things are related but can be independent, because it is possible to research health and sickness without curing specific patients, and it is possible to cure a patient without knowing how the cure worked.
Hello,
I am better studying the theory that is the basis of Bayesian optimization with a Gaussian Process and the acquisition function EI.
I would like to expose what I think I understand and ask you to correct me if I'm wrong.
The aim is to find the best ##\theta## parameters for a parametric...
Proof: Suppose that all primes except for 3 must have
remainder of 1 or 2 when divided by 3.
Then we have the form 3p+1 or 3p+2.
Note that the product of integers of the form 3p+1
also have the form...
I tried to use the degenerated perturbation theory but I'm having problems when it comes to diagonalizing the perturbation q1ˆ3q2ˆ3 which I think I need to find the first order correction.
I came across this upcoming book -- https://press.princeton.edu/books/hardcover/9780691174297/quantum-field-theory-as-simply-as-possible -- peer reviewed as it is published by Princeton University Press, which is due to be published in October. I've already ordered a copy coming from the UK. It...
I’m looking for a book treating the fluid dynamics of solidification, in particular in the presence of solute concentration gradients. I have found an amazing article by G. Worster titled “Perspectives in fluid dynamics; solidification of fluids”. Are there others?
In my lecture, it was explained that Kirchhoff's Rule is used when circuits are too "complicated" to simplify by combining resistances in series and parallel.
I do not understand in which cases I can simplify circuits by combining resistances, and on which cases I can only use Kirchoff's Rule...
Proof: Suppose for the sake of contradiction that gcd(a, b) \neq 1.
Then there exists a prime number k that divides both a+b and ab.
Note that k divides either a or b.
Since k divides a+b,
it follows that k divides b.
Thus, this is a...
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.128.040403
In QM, I was taught that the imaginary unit ##i## in wave functions is merely a mathematical tool. It has no physical meaning. We can always take the real part of the complex wave functions. Therefore, there should be some...
I apologize for the simple question, but it has been bothering me. One can write a relationship between groups, such as for example between Spin##(n)## and SO##(n)## as follows:
\begin{equation}
1 \rightarrow \{-1,+1 \} \rightarrow \text{Spin}(n) \rightarrow \text{SO}(n) \rightarrow 1...
Hello,
can somebody help me out please? just watched this video
so far understood but if motion changes the now frame its logic if the alien cylcles to the guy sitting that his time is slower and the guys time
will be in the future (time delitation). but when the alien is moving away how can...
I'm trying to prove the following:
##wt(x+y) \leq wt(x) + wt(y)##, where "wt(x)" is referring to the weight of a specific code word.
Proof:
For two code words ##x, y \in F^{n}_2##, we have the inequalities ##0 \leq wt(x)## and ##0 \leq wt(y)##. Adding these together, we have ##0 \leq wt(x) +...
I am reading pretty much everywhere that LET (Lorentz Ether Theory, or call it Neo-Lorentzian Relativity, or whatever theory that involves a preferred undetectable frame with some yet unknown properties that make all the moving objects with respect to this frame length contact and time dilate)...
Hi all, I just graduated from my master's program in theoretical physics. I did 60% of the coursework in high energy physics and rest in condensed matter theory plus a few experimental physics courses. I did my master's thesis in what can be called as theoretical cosmology, studying particle...
Research into the Higgs boson suggest that the universe is in a false vacuum but I heard many physicists do not take it seriously as they think that if it were true we cannot even exist as it would have wiped us out billions of years ago.
For example Katie Mack said that its like a piece of...
Hello, all. First, I want to apologize if this is not the correct forum or area of the forum for this question. Please direct me if I should be posting this somewhere else.
I have some questions regarding what I believe is best described as the "theory" of electrical capacitance. As my...
For example, after the Lagrangian is renormalized at 1-loop order, it is of the form
$$\mathcal{L}=\frac{1}{2}\partial^{\mu}\Phi\partial_{\mu}\Phi-\frac{1}{2}m^2\Phi^2-\frac{\lambda\Phi^4}{4!}-\frac{1}{2}\delta_m^2\Phi^2-\frac{\delta_{\lambda}\Phi^4}{4!}$$.
So if I were to attempt to find the...
Hey guys, I just wanted to know if you think that a membrane field theory could ellucidate the non-perturbative framework of M-theory?
Let me specify and explain what I mean by that: String field theory was intoduced to study the non-perturbative regime of string theory and some achievements in...
DLVO theory gives the curve of potential energy vs distance of two colloid particles. Potential energy curve is derived for colloids being only electrostatically stabilized and not sterically.
Looking at the image below which shows potential energy curve, we can see two local minima and one...
Hello! I'm a physics graduate who is interested to work in Mathematical Physics. I haven't taken any specialized maths courses in undergrad, and currently I have some time to self-learn. I have finished studying Real Analysis from "Understanding Analysis - Stephen Abbott" and I'm currently...
I'm not sure the following passage is so trivial as it was supposed to be: I mean, what does exactly prove it? That's my question.
The step is the following:
if ##P## has a root ##\alpha## in ##\mathbf L## - an extension of ##\mathbf K## of degree <= ##\frac n 2## where n is the degree of ##P##...
I understand that string theory has almost no testable predictions, however loop quantum gravity is an enticing candidate for only quantum gravity and it doesn't explain much of symmetry, constants, mixing angles etc in Standard model. There is obviously not enough evidence to create a full...
Given the unperturbed Hamiltonian ##H^0## and a small perturbating potential V. We have solved the original problem and have gotten a set of eigenvectors and eigenvalues of ##H^0##, and, say, two are degenerate:
$$ H^0 \ket a = E^0 \ket a$$
$$ H^0 \ket b = E^0 \ket b$$
Let's make them...
Or will confirm its predictions?
As far as I can tell, you can only raise the bar on the energies required from the accelerator, but you cannot give an upper bound, where beyond it the theory is doomed...
This isn't science... we might as well say we need infinite energies. 🙃
So far, I've taken Ordinary Differential Equations and Introduction to Mathematical Proof. My plan is to take "Introduction To Number Theory" for next semester in Spring 2022. But my professor told me that she won't use a textbook for this class. I was wondering what are some of the good...
I am doing private studies in string theory and am reading "A first course in string theory" by Barton Zwiebach. Below equation 6.52 the author
says "Since the second term on the right-hand side must vanish...". I do not understand why this term must vanish, and I would be grateful for an...
Hello folks, I am currently studying from Griffiths' Introduction to Quantum Mechanics and I've got a doubt about good quantum numbers that the text has been unable to solve.
As I understand it, good quantum numbers are the eigenvalues of the eigenvectors of an operator O that remain...
Of course, this question consisted of two parts. In the first part, we needed to calculate the first-order correction. It was easy. In all the books on quantum mechanics I saw, only first-order examples have been solved. So I really do not know how to solve it. Please explain the solution method...
Hi,
I'm a current senior in college, and am applying to grad. schools for fall 2022. I'm interested in high energy theory, and I have had some research experience in ads/cft correspondence, kaluza-klein theory, computational particle physics. However, I'm not certain as to which particular topic...
In this question, how does the step marked with 1 become the step marked with 2? I can see that the transitivity property of congruence is used, but I don’t know what exactly is going on here. Can someone please explain? Also at which step is Congruence Add and Multiply used?
Thanks...
Hello!
PS. This is not a Homework question, I am asking about a concept.
I am a Physics teacher from Brazil and last week one of the biggest Engineer universities here applied its entrance exam. However, a lot of teachers (including me) don't agree with one of the answers. Can you guys help...
If I plug the solution into the Schrodinger equation I get
$$(i \hbar \partial_t - H)\ket{\psi} = 0$$
Since I know that the zeroth-order expansion is lambda is already a solution I think this is equal to
$$(i \hbar \partial_t - H)e^{i\phi} e^{-i\gamma}\ket{\delta n} = 0$$
If now I carry on with...
In quantum chemistry, the MP rows (MP2, MP3, MP4, etc) can converge both quickly and slowly, and for some cases (e.g. CeI4 molecule) they even diverge instead of converging.
My question is quite philosophic: what is the “mathematical cornerstone”, or “philosophical cornerstone” of the...
Moderator's note: Spin off from previous thread due to advanced nature of topic.
There is classical field theory too, and GR is a relativistic classical field theory of the gravitational interaction. It's ironic that you fight for a geometrical-interpretation-only point of view and at the same...
I'm reading the https://www.phys.uniroma1.it/fisica/sites/default/files/DOTT_FISICA/MENU/03DOTTORANDI/TesiFin26/Urbani.pdf at paragrph 4.6.2 "The interaction term".
They write a right hand side:
< f(na,nb) f(nc,nd) f(ne,nf) >
and they want to use a symmetry, for example they assume that...
Are there any QFT books that use little to no math? If there is a little math that is okay. I don't know much about math. I am looking for good explanations on how it works without math. Any help would be great!
Hi, Folks,...new around here. Please excuse my naivete, but--
I have a problem with the physics behind GHG Theory/GW. Most discussions seem to center around absorbtion/transmission spectra of gases, their correlation with temperature, ala' Black Box radiation and such, and the fact that GHG...
It is often said that one of the drawbacks of the standard model is that it has many free parameters. My question is two-fold:
What exactly is a free parameter? My understanding is that the free parameters of a model/theory are the ones that cannot be predicted by the theory and need to be...
A lot of people say that Quantum Field theory (QFT) an Quantum Mechanics (QM) are equivalent. Yet, I've found others who dispute these claims. Among the counter-arguments (which I admittedly do not have the expertise to pick apart and check their validity in full) are the following:
1) While QFT...
-1st: Could someone give me some insight on what a ket-state refers to when dealing with a field? To my understand it tells us the probability amplitude of having each excitation at any spacetime point, but I don't know if this is accurate. Also, we solve the free field equation not for this...
It came to my attention yesterday this, from my ignorant point of view, amazing paper that describes what it looks as another Theory of Everything: https://arxiv.org/abs/2110.02062
If I didnt understand incorrectly, from first principles / a pre quantum theory (Trace Dynamics, 8D octonionic...
Homework Statement:: Mathematics to understand Quantum Scattering Theory
Relevant Equations:: Suitable math book to understand Quantum Scattering Theory
I need to study Scattering theory from Introduction to Quantum Mechanics by David Griffith. But I think I need to study mathematics first...
Let's say we have a big object like chair. According to Objective-collapse theory, is the wave of the chair collapsing and spreading out so fast we see it in one definite position or, does the chair collapse and it remains in this collapsed state longer than microscopic objects like atoms?