# Questions tagged [conventions]

A convention is a set of agreed, stipulated, or generally accepted norms. It typically helps common efficiency or understanding but is not required, as opposed to a strict standard or protocol.

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### Showing that the Wess-Zumino Lagrangian is invariant under a SUSY transformation

I want to show that the free Wess-Zumino Lagrangian is invariant under a SUSY transformation, e.g. following this reference (section 3.1). However, I have a hard time understanding the daggers and ...
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### Why use two spacetime indices to label Lorentz generators?

I've seen (e.g. in Srednicki) the following notation for the connection between a Lorentz transformation $\Lambda$ and the Lorentz generators $M^{\mu\nu}$: \begin{equation} {\Lambda^\mu}_\nu = {\left(...
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### Possible Error in Marion and Thornton's Classical Dynamics of Particles and Systems

so I was going over my notes on classical mechanics and just started to review rotation matrices which is the first topic the book starts with. On page 3 The rotation matrix associated with 1.2a and ...
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### In relativity, why does spacetime diagram have position on $x$-axis and time on $y$-axis?

In regular Newtonian physics, we use $x(t) - t$ graph to under position of a particle but why is it that in special relativity that we switch up the axis notation? I was seeing the lecture by Leonard ...
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### $B$-meson naming convention

An unbarred $B$-meson contains $\bar{b}$ (an anti-bottom quark), whereas a barred $\bar{B}$-meson contains $b$ (a bottom quark). What is the historical reason for this hellish naming convention?
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### How to calibrate potential function?

The original question: Given sphere with radius $R$ and charge $Q$, and an infinite wire that goes through the center of the sphere with charge density $\lambda$. Find an expression for the ...
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### Direction of Integration of Electrostatic force over a circular arc, direction of the resultant force changing with interchange in limits?

Problem: A uniformly charged circular arc with linear charge density $m$ subtends angle $\theta$, find the net force acting on a charge placed at its center if total charge of the arc is $Q$ and the ...
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### Which basis 2-form elements represent positive traversals in Minkowski 4-space?

I'm certain some of this relies on arbitrary choice, for even in Euclidean 3-space, there is no a priori preferred choice of left versus right hand coordinates. In fact according to Einstein: There ...
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### Why the gravitational potential energy at infinity is zero?

If an object is taken from earth's surface to infinity, it's gravitational potential energy becomes zero (always taken as zero), but it doesn't make any sense as energy can never be destroyed so where ...
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### Derivation of the Electromagnetic Stress-Energy Tensor in Flat Space-time

I am working on deriving the electromagnetic stress energy tensor using the electromagnetic tensor in the $(-, +, +, +)$ sign convention. However, I have hit a snag and cannot figure out where I have ...
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### Why do we normalize the radial and the angular parts of a spherical wavefunction separately?

I'm trying to revise the Quantum Mechanical model of the Hydrogen atom, and I understand all the methods involved, including separating the wavefunction into its radial and angular parts, solving all ...
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### Why is $\Delta V = - \int E \cdot dr$ when charge is moving from lower potential to higher potential?

In a parallel plate capacitor, charge $q$ is travelling from negative to positive plate. Why is $\Delta V$ negative? Every book explains it by saying $\Delta U = -W$, but this equation came when we ...
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### Why is the electric potential at a distance of $R$ from a point charge $q$ equal to $\frac{-q}{4\pi\varepsilon_0 R}$

My textbook mentions that the electric potential at distance of $R$ from a point charge $q$ will be given by $\dfrac{-q}{4\pi\varepsilon_0 R}$. I don't understand why the negative symbol appears here. ...
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### What exactly does voltage refer to?

Considering a charge moving down a wire, the electric field does work on the charges. The work done by the electric field can have two outcomes:it can increase the kinetic energy of the charge ...
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### Can we make uniformity in marking zero potential? Say it at earths surface or at infinity from earths surface?

The gravitational potential energy at infinity os supposed to be zero. Since body always moves towards lower potential, the gravitational potential is taken as negative so that gravitational potential ...
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### Are the Lowering and Raising Operators of QM the same as those of QFT?

We know that the lowering and raising operators in quantum mechanics are defined as \begin{array}{l} a =\frac{1}{\sqrt{2}}(X+i P) \\ a^{\dagger} =\frac{1}{\sqrt{2}}(X-i P), \end{array} respectively. I ...
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im having difficulty understanding the criteria of signs settled down by BSL transport phenomena in the derivation of Stokes law in chapter 2 at the page 59 it takes the molecular momentum-flux tensor ...
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### Hypercharge of the Higgs field

I am puzzled by the hypercharge of the Higgs field. Under the entry "Higgs Mechanism" in Wikipedia, it is written: Its (weak hypercharge) U(1) charge is 1 However, under the entry "...
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### Sign of counterterm vertex factor (Srednicki)?

My question is about a mere minus sign which, although irrelevant in my specific problem (as will be shown), I fear may bite me later on. In Srednicki chapter 14, the author is computing the 1-loop ...