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Questions tagged [definition]

The definition tag is used in situations where the question is either about how some term or concept is defined or where the validity of an answer depends on a subtle definition of some term or concept used in the question.

2
votes
1answer
17 views

What is $\mathbb{Z}_2$ Parity?

While reading about exotic decays of Higgs boson one of the simplest interaction that we come up with which leads to BSM decays is: $$\Delta L = \frac{\zeta}{2}s^{2}|H|^{2}.$$ This is the ...
2
votes
0answers
25 views

Angular momentum for asymptotic states in black hole spacetime

Consider a massless KG field propagating in a gravitational collapse spacetime which produced a black hole. Neglect backscattering for a moment. In that case, when asymptotic quantization is ...
-3
votes
1answer
60 views

Dark energy and dark matter difference

From the rotation curve of spiral galaxy it is found that for (>>r ) the total mass is not concentrated at the centre but varies as ~r for which the rotational velocities of the stars far from the ...
0
votes
1answer
33 views

What is a precise definition for laminar flow that includes “laminar vortex-shedding”?

I can't find a definition for laminar flow that includes vortex structures. See paper: Numerical calculation of laminar vortex-shedding flow past cylinders and countless others when googled.
8
votes
0answers
121 views
+50

Why this is classical correlation and not full (classical + quantum) correlation?

Let a quantum system be given which has two subsystems $A$ and $B$ so that the Hilbert space decomposes $\mathscr{H}\simeq \mathscr{H}_A\otimes \mathscr{H}_B$. If the state of the system is $\rho$, ...
0
votes
2answers
65 views

Is force really defined by the second axiom of Newtonian mechanics? [duplicate]

Many people claim that force is defined by the second axiom of Newtonian Mechanics, which is: "In an inertial reference frame, the rate of change of momentum of a particle equals the sum of the ...
7
votes
6answers
347 views

So is quantum entanglement actually FTL “communication” or is it mundane pre-determination?

I have to say right off the bat, I'm a little frustrated that there seem to be very contradictory answers about this, at least to a layman like me. If two particles are entangled and you separate them ...
4
votes
1answer
137 views

What is a definition of the trace norm?

I have found that (one?) definition of the trace norm is $$\mid\mid A\mid\mid = \sqrt{A^*A} \tag{1}$$ but now I am reading this paper where (on page 4) it says In particular, we will restrict ...
0
votes
3answers
51 views

Confusion Regarding Hookes law

I am used to seeing Hookes law in the form: $F = kx$ but in another one of my books it gives the equation: $\\ F = \frac{\lambda x}{l}$ where $l$ is the unstretched length, $x$ is the extension and $\...
0
votes
2answers
63 views

What does Dirac mean by “proximity”?

I was reading Dirac's "The Principles of Quantum Mechanics" and on page 7 he makes the following statement: "Like the fundamental concepts (proximity, identity) which everyone must learn on his ...
-1
votes
0answers
123 views

What is “one over something”? [migrated]

In my physics class when the tutor talks a value of something, they say that will be "one over something", I'm not sure what this is and I cannot ask because it seems like everyone else knows what he ...
0
votes
0answers
28 views

Relation between computation of curl and divergence and their formal definitions

both divergence and curl of a vector field have a formal definition, however, we don't use these definitions when we compute the divergence or curl. so can we just derive the computations from the ...
8
votes
2answers
2k views

What is the difference between a neutrino and an electron neutrino?

So, what is the difference between a neutrino and an electron neutrino? Like how does the term 'electron' made a difference? Also, what is the difference between an antineutrino and an electron ...
3
votes
2answers
76 views

Can magnitude be negative?

My teacher told that magnitude is the positive value of that quantity or the modulus of that quantity. he also told that vector quantities have both magnitude and direction and scalar quantities have ...
4
votes
2answers
93 views

Is length an extensive property?

From my experience, volume, surface and length are extensive properties. Indeed : the reunion of two cubes of 1 $m^3$ leads to a cube of 2 $m^3$ the reunion of two tiles of 1 $m^2$ leads to a tile ...
1
vote
1answer
27 views

What's the difference between twisted light and light of circular polarization?

Circular polarization: https://en.wikipedia.org/wiki/Circular_polarization Orbital angular momentum of light: https://en.wikipedia.org/wiki/Orbital_angular_momentum_of_light From point of view, ...
3
votes
1answer
120 views

What is the definition of “force” in quantum field theory?

In quantum field theory, there are certain interactions that we seem to associate with the action of "forces." For example, the exchange of a gauge boson between two matter particles is associated ...
0
votes
2answers
75 views

These terms are so foreign to me that they feel like unnecessary jargon; what do these terms mean, and are they relatively common?

No pun intended in the title. ;) I am having trouble understanding this sentence on Wikipedia's page for Unified Field Theory: Governed by a global event $\lambda$ under the universal topology, ...
0
votes
1answer
49 views

What does $\mathcal{N}$ refer to in Gauge theories?

Context: I am a second-year (undergraduate) physics major applying for a summer research position. The investigator is working on Quiver Gauge Theories and in response to my inquiry email he told me ...
3
votes
4answers
310 views

What are the differences between specific latent heat and latent heat?

What are the differences between specific latent heat and latent heat? As far as I know, latent heat is the heat required or released during the change of state, without change of temperature. So ...
0
votes
0answers
38 views

What is the symmetry of a Hamiltonian?

Recently while I was reading a paper on integrability of Rabi model by D Braak. In this paper there is a discussion about the symmetry of a model and that in the case of the Rabi model it is $\mathbb{...
0
votes
0answers
42 views

Difference between pure and thermal states

As far as I know by inserting a harmonic potential $V(x) = \frac{1}{2}m \omega x^2$ into the time-independent schrödinger equation I can obtain the wave-functions eigenstates and eigenvalues (energies)...
0
votes
1answer
30 views

Should specific heat capacity be defined as “the numerical value of the quantity of heat…” or simply the “quantity of heat”?

Sorry for this vague question but I'd just like to ask a question that my teachers weren't able to give a really satisfactory answer to. In my notes the specific heat capacity is defined with the ...
0
votes
1answer
29 views

If oscillatory motion is not simple (or chaotic), is it then by definition complex?

I'm trying to logically deduce or show that a specific type of motion is complex. It is two-dimensional oscillatory motion that can be expressed by coupled second order non-linear differential ...
1
vote
0answers
37 views

Difference between Scattering and Reflection

I am confused: What exactly is the difference between optical scattering and optical reflection? To me, both terms are distinguished by where we place the observation plane. Reflection: Observation ...
0
votes
3answers
183 views

What is quasi-static process?

What is the formal definition of quasi static process? I am accustomed with it a bit intuitively, i want to know the formal definition of this. At some source I found the definition of somewhat ...
0
votes
1answer
61 views

Definition of angular velocity vector of $B$ in $A$ - Strange notation

I found the following definition of angular velocity vector of B in A at page 49 of the book "Thomas R. Kane, Peter W. Likins, David A. Levinson - Spacecraft Dynamics - McGraw-Hill (1981)": The ...
1
vote
3answers
38 views

$Q$-factor for damped oscillator (not driven)?

How would this be defined? Some of the Q-factor definitions I have encountered include: $$Q=2\pi\frac{Energy \space stored}{Mean \space power \space per \space cycle}\\Q=2\pi\frac{Energy \space ...
7
votes
1answer
84 views

Distinct choice of partition in the Path Integral

Practically all books in Quantum Mechanics and Quantum Field Theory define the non-relativistic path integral by taking one interval $[a,b]$ and breaking it up into $N$ subintervals of equal length. ...
0
votes
3answers
64 views

What's the difference between gravitational attraction and weight? [duplicate]

What exactly is gravitational attraction? In my textbook it was quoted " all objects both tiny and large objects are attracted to the earth. This is known as gravitational attraction, or the force due ...
-1
votes
2answers
68 views

Why is work defined with respect to distance rather than time? [duplicate]

The common way of finding the work done on some object is by applying the equation: force*displacement. However, suppose we apply a force of F newtons on an object of mass M for a duration of T ...
0
votes
2answers
58 views

Impulse as the time derivative of force

Momentum is the time derivative of force. $F = \frac{dp}{dt}$. But isn't impulse $J=Ft$, $F=\frac{J}{t}$? Can impulse be the time derivative of force too, or is it just defined as an integral?
0
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3answers
45 views

A question on rigid body dynamics.

What is the intuition for angular momentum of a point mass relative to a inertial point? Does the definition of angular momentum of a point mass holds true in non inertial reference frame? How?
9
votes
1answer
222 views

What is the actual definition of conformal invariance?

I've seen a large variety of slightly different definitions of conformal invariance. For simplicity I'll only consider scale invariance, which is already confusing enough. Some of the definitions are: ...
0
votes
3answers
96 views

How can we define energy other than the definition that it's a capability to do work? [closed]

It is actually a property of energy that it can do some work not an actual mean to define it because we cannot define a thing on the basis of what it is doing or what it can do.
0
votes
2answers
85 views

Phase Velocity Derivation

I spend few hours trying to derive phase velocity of sinusoidal wave $$\cos(kx - \omega t).$$ I know that it must be equal to $\omega \over k$ but after banging my head for few hours and trying to ...
2
votes
4answers
114 views

Why is escape velocity independent of direction of projection?

However, for any body projected with a velocity less then the escape velocity, the final maximum height will vary with variation in angle of projection. But why is this not the case in case of ...
2
votes
1answer
72 views

Is there any special significance of force field in physics?

What is the formal definition of force field? Which is more fundamental force or field? Do field exist in nature (as force do i think as per section 12-1 of Feynman lecture volume 1, and page 8,9 of ...
1
vote
1answer
42 views

Is there a “standard” Newton?

Basic SI units have definitions through experiments that seems to imply a pretty obvious setup. Is there a standard experiment for calibrating Newtons? The definition is the force needed to cause a ...
2
votes
1answer
44 views

States of classical general relativity

In Classical Mechanics a state of a system is either a pair $(q,p)$ or $(q,\dot{q})$ depending if we formulate the theory on the tangent or cotangent bundle of the configuration space. The evolution ...
4
votes
5answers
165 views

Could someone explain what is a potential?

In many part of physics, me talk about potential (electrical potential, gravitation potential, elastic potential...). All those definition looks very different, and I would like to know how all those ...
6
votes
1answer
83 views

GR with Torsion: Definition of contorsion

I start doing some computations in manifolds with non vanishing torsion and things are getting a bit confused, basically because of notations and definitions. I understand that in presence of non ...
2
votes
1answer
49 views

Definition of equilibrium for thermodynamics and statistical mechanics

Is the definition of equilibrium for thermodynamics and statistical mechanics the same? From my understanding, a system is in thermodynamic equilibrium if its macroscopic variables are not changing. ...
6
votes
2answers
163 views

Is this actually the rigorous definition of the path integral in Quantum Mechanics?

Let a quantum system with a single degree of freedom be given. We want to define the path integral so that we get the representation for the propagator as $$\langle q' |e^{-iHT}|q\rangle=\int_{x(a)=...
2
votes
1answer
59 views

Time Travel, CTC and Causal Loop

What is the difference between a closed timelike curve and a causal loop? If someone is travelling in a closed timelike curve, are they also in a causal loop?
2
votes
4answers
102 views

Thermodynamics second law variational statement query

In thermodynamics as I understand entropy is a state function. A state function is a property whose value does not depend on the path taken to reach that specific value. In contrast, functions that ...
0
votes
0answers
48 views

Superstate vs superposition

Is superstate the phase space of a superposition that includes subsets? It seems like superstate is not used as a word that often, and usually seems to be a synonym for superposition. Can anyone give ...
-2
votes
2answers
174 views

Isn't definition of potential energy a vague definition? [duplicate]

Why do we define potential energy? If we know the essence of defining work then isn't defining potential energy useless?
5
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2answers
94 views

Will the SI units need redefining ever again?

Up until recently, there were obvious problems with the SI definitions of fundamental units, like bits rubbing off the kilogram prototypes (or mercury vapour absorption), and the water used for the ...
1
vote
2answers
55 views

Strange super script notation $^{(4)}R$ in the textbook Numerical Relativity

In Numerical Relativity by Thomas W. Baumgarte and Stuart L. Shapiro. There are bunch of superscript $(4)$ over $T,\Gamma, R$ i.e. $^{(4)}\Gamma^a_{bc}$ _ $^{(4)}R_{abcd}$ _ $^{(4)}R$ ... (...