# What is Convention: Definition and 184 Discussions

A convention center (American English; or conference centre in Commonwealth English) is a large building that is designed to hold a convention, where individuals and groups gather to promote and share common interests. Convention centers typically offer sufficient floor area to accommodate several thousand attendees. Very large venues, suitable for major trade shows, are sometimes known as exhibition halls. Convention centers typically have at least one auditorium and may also contain concert halls, lecture halls, meeting rooms, and conference rooms. Some large resort area hotels include a convention center.

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1. ### I Relativity & Simultaneity Convention: Meaning & Impact

Hi all, I have been figuring out relativity. I was just wondering how meaningful the simultaneity convention is, how meaningful it is for say something a million light years away to be on our plane of simultaneity. I'm guessing not very, we must really wait for light to get to use to have...
2. ### I Einstein summation convention in QM

Hi For an operator A we have Aψn = anψn ; the matrix elements of the operator A are given by Amn= anδmn My question is : is this an abuse of Einstein summation convention or is that convention not used in QM ? Thanks
3. ### I Understanding Conventions in Engineering: The Role of Rules and Consistency

(I admit this might be better in the mechanical engineering forum, but let me ask, and the moderator can decide) What is a "convention?" For example, in elasticity, we have a stress tensor. If a coordinate axis is in one direction, positive, we state the the convention is that the stress is...
4. ### I Understanding the phrase "simultaneity convention"

I have a number of questions about some S.R. basics. The answer to one question may affect the next, so I will try to focus on one question at a time. The question here is about the possible range of “simultaneity conventions.” We place an observer at location A. This observer releases a photon...
5. ### I A couple questions about the Riemann Tensor, definition and convention

According to Wikipedia, the definition of the Riemann Tensor can be taken as ##R^{\rho}_{\sigma \mu \nu} = dx^{\rho}[\nabla_{\mu},\nabla_{\nu}]\partial_{\sigma}##. Note that I dropped the Lie Bracket term and used the commutator since I'm looking at calculating this w.r.t. the basis. I...
6. ### Simplified rocket lateral dynamics model sign convention

Hi everyone :smile: . I had came across a simplified simplified rocket lateral dynamics model :https://github.com/build-week/hover-jet/blob/feature/start-design-scripts/design-scripts/jet_vane_speed.ipynb . It has vanes at the exit which generate lift force and can control the rocket...
7. ### I Einstein summation convention confusion

Hi If i have a vector r = ( x1 , x2 , x3) then i can write r2 as xixi where the i is summed over because it occurs twice. Now is xixi the same as xi2 ? I have come across an example where they are used as equivalent but i am confused because xi2 seems to be the square of just one component of r...
8. ### Engineering Cadence Transformer dot convention and polarity (xfmr)

Here is the circuit... Here is my work so far in cadence (I haven't put in values for other components in because the moment I saw the dot convention I started trying to figure that out). Where I'm at -There apparently isn't a way in Cadence Virtuoso (the program my class uses) to change the...
9. ### Sign convention of internal forces in vertical bars for bending moment

Hello: I was looking for a widespread convention (akin to Hibbeler's, Beer's, etc) that deals with the sign convention of a vertical bar for bending moments. For example, without knowing in advance, how do I draw the bending moment at a cut passing through point E in the figure attached? Beam...
10. ### I Does Lorentz invariance imply Einstein's synchronization convention?

Hi, I've read a number of posts here on PF about Einstein's clock synchronization convention. In the context of SR we know the transformation law between inertial frame's coordinates is actually the Lorentz one. The invariant speed for Lorentz transformation is c (actually it coincides with...
11. ### Is the Configuration of Magnetic Fields Only a Convention?

If I understand correctly, the concept of electric and magnetic fields originated with Faraday and was developed by reconceptualizing forces acting at-a-distance. For example, the electric field concept was developed by looking at the force on a test charge in the presence of a source charge...
12. ### Normalisation of eigenvectors convention for exponentiating matrices

Hi, I just have a quick question when I was working through a linear algebra homework problem. We are given a matrix A = \begin{pmatrix} 2 & -2 \\ 1 & -1 \end{pmatrix} and are asked to compute e^{A} . In earlier parts of the question, we prove the identities A = V \Lambda V^{-1} and e^{A}...
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### B Is the Doppler Effect Formula Different for Sources in Different Regions?

If the source is at ##(t,0)## in ##S## and the receiver is at ##(t',0)## in ##S'## which moves at ##\beta_x## w.r.t. ##S##, then by considering two crests at ##(0,0)## and ##(T_s, 0)## in the source frame ##S## and transforming these events into ##S'## we can derive that ##\lambda_{r} =...

41. ### A Is spacetime orientation a convention?

I thought this was an easy enough question but then I managed to obtain arguments both for and agaisnt it and confused myself. Is there a clear demonstrable answer to this question in relativistic field theory? Is spatial and temporal orientation a convention?
42. ### B Isn't the Riemann Hypothesis just a convention?

If the zeta function intersects the critical line when the real part is 1/2, then it will intersect some other line when some other real part is used. Isn't the Riemann Hypothesis just based on a particular convention for the critical line?
43. ### Moments -- sign convention in beam

Homework Statement In this question , we can see that in teh second picture , the 12.86kNm is in clockwise direction at the right of span BC . Homework EquationsThe Attempt at a Solution In meachnic of materials , i learned that when the beam curve upwards ( U shape) , then it has positive...
44. ### I Convention of order of operations

To what extent is the PEMDAS order of operations convention, and to what extent is this convention significant? For example, how would math change if we stipulated that ##1+2*3 = 3*3 = 9##? Would it be the same or would it be completely different?
45. ### Organizing a PF Meeting or Convention: Ideas & Discussion

Has there ever been an attempt to organize a PF meeting or convention? Personally, I think that would be a great thing for everyone to be able to meet the people they talk to here, if they don't already know them. Obviously, though, there are some immediate issues such as the worldwide PF...
46. ### Sign convention of shear stress confusion

Homework Statement In my book , i was told that when the shear stress turn a plane of element clockwise , then the shear stress is positive , In this question , we can notice the shear stress of 40 will turn the plane clockwise , why the author plot the stress at A = (80,-40) ? Shouldn't it be...
47. ### I Question on convention - R vs r using universal law of grav.

I have a question on convention regarding the universal law of gravitation formula. Sometimes the distance is represented with the lowercase r and sometimes with the uppercase R. Why is it listed two different ways? I am thinking that r is the total distance and R is the radial distance, no...
48. ### I Is the convergence of an infinite series mere convention?

It seems to me that convergence rounds away the possibility of there being a smallest constituent part of reality. For instance, adding 1/2 + 1/4 + 1/8 . . . etc. would never become 1, since there would always be an infinitely small fraction that made the second half unreachable relative to the...
49. ### Sign convention problem in momentum calulations

Homework Statement Particle A has a mass of 1kg and velocity 2x10^8m/s to the right and collides with a stationary particle B that has a mass of 4kg. after the collision, particle A moves to the left with a velocity(v) and particle B moves to the right with a velocity of 1x10^7 m/s. calcuate...
50. ### Sign convention of shear stress

Homework Statement In the in the first image , it's shown that the shear stresses has positive sign, whereas in the second image e (circled blue part) has different sign convention,which is positive and negative, which is correct? Homework EquationsThe Attempt at a Solution IMO, the second...