# Tagged Questions

A set of numbers used to quantify location in space.

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### Why is light described by a null geodesic?

I'm trying to wrap my head around how geodesics describe trajectories at the moment. I get that for events to be causally connected, they must be connected by a timelike curve, so free objects must ...
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### Stationary v/s Static

Blau, in his GR book, says that a stationary and spherically symmetric metric is automatically static. He says this easily follows from the fact that for a stationary metric, and in spherical symmetry,...
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### Why centripetal force does not increase the value of tangential velocity?

I found in a text book that the value does not change because the centripetal force is perpendicular to the tangential velocity. But I am confused, because a vector can have a component, which is ...
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### Description of charged sphere with Heaviside function in cylindrical coordinates

I need to describe density of charge of uniformly charged sphere (radius R, total charge Q, position of centre (0,0,0)) with Dirac delta function and Heaviside step function. The hard part is to ...
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### Determination of Euler angles from known angles between the axes of two coordinate systems

Suppose there is a unprimed coordinate system XYZ, tilted w.r.t. a primed coordinate system but their origins coincide. Let the angle between $X,X^\prime$, $Y,Y^\prime$ and $Z,Z^\prime$ are ...
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### Why do Newton's laws hold in a normal and tangential coordinate system?

In my book it says: When applying the equations of motions, it is important that the acceleration of a particle be measured with respect to a reference frame that is either fixed or translates ...
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### Coordinate system for crystallographic groups

In the International Tables for Crystallography for each crystallographic group an asymmetric unit is supplied (mathematicians call this a fundamental domain of the group). This region is a bounded ...
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### Locally flat coordinate and Locally inertial frame

I am having some doubts on myself regarding the above concepts in General Relativity. First, I want to point out how I understand them so far. A male observer follows a timelike worldline ($\gamma$) ...
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### Marsden and Hughes Mathematical Foundations of Elasticity Derivation

in the beginning of the book they discuss transformation between coordinate systems and they use this to show that the velocity of a point transforms into that coordinate system;, in terms of the ...
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### What is the difference between active and passive transformations in Quantum Mechanics?

I am trying to understand what each transformation means and what their differences are but many books that don't state which transformation they are referring to make it a bit confusing to understand ...
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### Field transformations

I'm reading Maggiore's book "A modern introduction to quantum field theory" and I'm very confused by what he did in chapter 2.6 page 31 eq. (2.80). He basically wants to find the generators of the ...
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