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Integral-Solving

I know this is a very naive question but during my quantum optics study, I often come across the following kind of integrals. Sometimes there is an identity to get it solved but other times there is ...
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2 votes
0 answers
27 views

Measure small mass change on heavy item [closed]

I need to measure the change in mass on a large number of components we are developing with a size of a large orange and weighing between 0.3 and 1 kg to an accuracy of sub 10x10-6 kg. The mass will ...
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-2 votes
0 answers
56 views

The Universe is a brain? [closed]

This research paper here shows extraordinary qualitative and quantitative physical similarities of the brain with the structure of the Universe Cosmic Web which it proves cannot be a coincidence. Why ...
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-5 votes
0 answers
32 views

Lord Kelvin's vortex theory of atoms may prove today to be more relative to particle physics? [closed]

Lord Kelvin's attempt to explain the atom's of different elements of the periodic table, inner structure as energy vortices of different types (i.e. knot theory) may today be more applicable for sub ...
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I tried to do it by solve in both dir. of acc. then get confused where i did it wrong why we can only do thus question by song work energy theorem [closed]

Chapter :magnetic effect of current magnetic force on charge or current
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2 votes
0 answers
32 views

Query regarding motion of a cylinder [closed]

I need help understanding the motion of this cylinder... Cylinder A of mass M is resting on two smooth edges, one fixed and other is that of a block B. At an instant block B is pulled toward left with ...
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1 vote
0 answers
46 views

Scalar curvature from Riemannian metric

I want to compute the scalar curvature for points on an empirical manifold (sampled data). I have already an algorithm that learns the Riemannian metric and computes geodesics, so from the metric I ...
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-1 votes
0 answers
59 views

Is there an experiment that shows the strong force grows with distance?

Is there an experiment that shows the strong interaction increases with distance?
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1 answer
24 views

Collision Paradox time inversion [closed]

I am currently working on an physics engine to simulate collisions of balls. I have one blue and one red ball, the red ball moves forward in time, while the blue one moves backwards in time. Basically ...
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How to quantify the one-way flow of information in Markovian dynamics

It is said that in the Born-Markovian dynamics (Master equation), the information flow is one way, i.e. from the system to the environment. How to understand this sentence? Is there a quantity of the ...
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0 answers
7 views

Why do Liquid-state NMR qubit only work with fermionic nuclei?

"The ideal picture of liquid state NMR (LSNMR) quantum information processing (QIP) is based on a molecule in which some of its atom's nuclei behave as spin-½ systems." https://en.wikipedia....
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17 views

Complete set of commuting observables for the non-interacting light field

The Hilbert space for the non-interacting electromagnetic field is the bosonic Fock space $\mathcal{B}(L^2(\mathbb{R}^3) \otimes \mathbb{C}^2)$. Here, $L^2(\mathbb{R}^3)$ is the space of square-...
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0 answers
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Solid mechanics [closed]

my approach I have plotted the graph using wolfram alpha but cannot understand how to plot a double y plot
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2 answers
29 views

Motion of a sphere at the end of a structure

I need help understanding the motion of the sphere given in the figure below... The centre of this sphere lies at some horizontal distance from the vertical line ( If it is extended ) Will it have a ...
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2 votes
2 answers
26 views

Does the intermolecular forces change during phase transition?

When water is heated but not yet boiling, I understand that the intermolecular attraction does not change, but the molecules vibrate more. But when water boils to gas, does the forces of attraction ...
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0 answers
41 views

Calculus of Variations, Noether's Theorem, need help understanding and solving this problem

I have been given the following problem: Investigate whether the functional $I=\int_{t_1}^{t_2}t\dot{x}^2dt$ is invariant under the transformation $\bar{t}=t+\epsilon$ and $\bar{x}=x$, with $\epsilon$...
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Why the density perturbation of Newtonian and Comoving gauge are the same in the sub-horizon limit?

In Daniel Baumann's Cosmology lecture note for UvA Masters Course Cosmology: http://cosmology.amsterdam/education/cosmology/, when discussing the cosmic perturbation theory of matter, the author ...
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8 views

What is the effect of increasing the size interval in the generalized dynamic equation (GDE) to simulate an evolving aerosol?

The following differential equation allows me to calculate the the number concentration of aerosol particles from 2 nm to 3 nm. $$\frac{dN_2{_-{_3}}}{dt}=J_2-J_3-N_2{_-{_3}}.CoagS_2{_-{_3}}$$ In the ...
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0 answers
19 views

Calculate total number of fluence on a moving detector

We have a radiation zone emanating from a source located at $(x_0, y_0, z_0)$. We also happen to have the flux due to this source measured in a 3d cylindrical grid surrounding the source with a flux, $...
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  • 1
1 vote
1 answer
48 views

Integral of time dependent Hamiltonian

Computing the time evolution of a quantum system described by a time-dependent Hamiltonian, $H(t)$, amounts to constructing the time evolution operator $$U = \mathcal{T} \exp \Biggl( -i \int_{0}^{t} \...
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  • 143
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0 answers
50 views

To what extent does Hardy recover quantum mechanics?

In his 2001 paper, Hardy claims to recover quantum mechanics from five reasonable axioms. I am a mathematician and honestly admit that I don't understand the paper. I would like to understand exactly ...
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  • 399
0 votes
2 answers
34 views

Friction between ground and object

In figure-1,a man is walking on ground with an acceleration $a$ forward. Now since the only force in $+x$ direction is the the frictional force,we say that the frictional force is taking the man ...
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  • 683
1 vote
3 answers
53 views

Besides traveling at the speed of light, how can we be sure that it is possible to have energy and momentum without mass?

How can we be sure that it is possible to have energy and momentum without mass? If something were to continually lose energy, would it not also lose a corresponding amount of mass? I understand that ...
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0 votes
0 answers
21 views

Question regarding the Fourier Transform of the Hubbard Hamiltonian

If you Fourier transform the Hubbard Hamiltonian $$ H = \sum_{ij \sigma} T_{ij} c^{\dagger}_{i \sigma} c_{j \sigma} + \frac{U}{2} \sum_{i \sigma} n_{i \sigma} n_{i \overline{\sigma}} $$ via $$ c^{\...
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0 votes
1 answer
30 views

What is the mechanism behind Wet Surface Writing Pens?

I came across pens/markers Eg- here and here which can write on a wet surface. I want to know the mechanism behind them- their ink, or the delivery system, their nibs. I need these information for a ...
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  • 101
0 votes
1 answer
19 views

Ferromagnetic vs Paramagnetic

I know a ferromagnetic material (e.g iron) losses its ferromagnetic properties over the Curie temperate. What are the other methods to make iron paramagnetic from its ferromagnetic stage? Please ...
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-1 votes
0 answers
11 views

According to the standard model, if the universe were not expanding and treated as a single, closed system, would energy be conserved?

It is said that energy conservation requires the reversibility of time, but space expanding breaks that condition. If the universe was not expanding and treated as a single, closed system, is energy ...
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0 votes
1 answer
31 views

Deriving equation describing fermion-antifermion field

We know the Lagrangian of massless interacting Dirac field $\mathcal{L}=\bar{\psi}i\gamma^\mu(\partial_\mu-iA_\mu)\psi$ Now consider charge conjugation operator $C=i\gamma^2$ The Lagrangian for charge ...
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6 votes
2 answers
369 views

Does kinetic energy of an object curve spacetime? [duplicate]

Based on general relativity mass and energy distribution curves spacetime. Thus, if an object with 1kg rest mass moves with constant speed and has a speed very close to speed of light, then it has an ...
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  • 885
5 votes
9 answers
3k views

Can heat(?) flow from a cold object to hot object?

When we dip a spoon (stainless steel) into ice cream, does it becomes cold or stay the same temperature? If it does, can we say that heat(?) can flow from cold to hot objects? Is this the reason ...
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1 vote
0 answers
39 views

Physics of $N$ linked pendulums connected on two sides

I was looking for information on how a series of pendulums linked together (not coupled but the bob of one pendulum connected to the pivot of another like in a double pendulum) would act when walked ...
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0 votes
1 answer
12 views

Does superconductivity enable an analog to magnetic field flyback for the electric field?

Flyback being the act of rapid collapse of the magnetic field in a fractions of a second in order to abuse the law of induction $$L\frac{\mathrm di}{\mathrm dt}=V,$$ which occurs because resistance ...
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3 votes
1 answer
61 views

Postulates of statistical mechanics

Do we have postulates of statistical mechanics the way we have for quantum mechanics?
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0 votes
0 answers
14 views

Why does Pseudorapidity distribution have two peaks?

I found plots(fig2) that state that it is the sum of two gaussian distributions, but I am not able to understand its physical significance. Any help would be appreciated.[PS Why does rapidity not have ...
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-4 votes
1 answer
29 views

Solve this question according to quantum mechanics for a free particle ($V=0$) [closed]

]1 $~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~$
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1 vote
0 answers
37 views

Calculation of Electric field using centre of mass

One of my Physics teacher told me how to calculate Electric field from centre of mass using Mathematical similarity- Write the Coulomb's law in vector form $\vec{E}=\frac{K Q}{R^{3}} \vec{R}$ $\vec{\...
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0 votes
0 answers
35 views

What is aerodynamics function of front active lip spoiler?

In this video is active front bumper lip spoiler. Also here picture show flexibile plate in front of front tyer. What are aerodynmics function of these two devices?
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  • 226
1 vote
1 answer
43 views

Friction and electromagnetic force

What is the relationship between friction and electromagnetic force? At microscopic level, how does electromagnetic force cause friction?
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  • 11
0 votes
0 answers
18 views

What is the relationship between non-Reciprocal and non-Hermite?

In paper[Non-Hermitian morphing of topological modes], the author realizes a non-Hermite ssh model by constructing an active mechanical lattice, the united cell consisting of 2 sites A、B. $$ \mathrm{d}...
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4 votes
2 answers
397 views

What is the stress-energy tensor in this case?

In case of static point mass we have the following stress energy tensor $$T_{00}=m\delta^3(\vec{r})$$ And other components are zero. What are the components of this tensor in case of moving point mass ...
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1 vote
3 answers
97 views

Why gravitational constant $G$ does not have the factor of $4π$?

We know that electrostatic constant $K=\frac{1}{4\pi\epsilon}$. This $4\pi$ came from the surface area of the surface in which charge is enclosed. Then, why don't gravitational constant has the factor ...
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1 vote
1 answer
17 views

General expression for time evolution operator in terms of path integral

Given that I know that the time evolution operator $U^{i\rightarrow f}$ for initial and final states $|\psi^{i,f}\rangle$, defined by $|\psi^f\rangle:=U^{i\rightarrow f}|\psi^i\rangle$, how do I show ...
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  • 181
0 votes
0 answers
18 views

Does it require energy to generate an electric field as well as a magnetic field?

It is known that the electric field as well as the magnetic field carriers energy, so I wonder is the energy of the fields generated by a charge originated from the kinetic energy of the charge?
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0 answers
9 views

System where Energy Dissipates but Frequency Increases

Is there any example of an oscillating system where, as energy is dissipated by some external force, the frequency of the system's oscillation increases? One of the questions from 2022's IYPT asked ...
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0 votes
0 answers
13 views

Effect of radius of circular flight on energy consumption of rotary wing UAV [closed]

We consider a rotary wing UAV flying in circles arround a stationary point. We do not consider wind. We consider static speed - acceleration equal to 0. I have read in many papers what makes sense - ...
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  • 101
1 vote
0 answers
11 views

Simulating electromagnetic propagation from a vector plane

I am using finite element software (COMSOL) to study Photonic Slab, because the Slab is in 3D, it needs quite a lot of periodic unit to observe desired effect. and periodic boundary condition is not ...
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0 votes
2 answers
31 views

What is the entropy associated with a diffusion process?

Is it possible to calculate entropy from the solution of a diffusion equation(with natural boundary conditions) by using the formula of Shanon entropy? Could anyone help me to understand the entropic ...
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  • 39
0 votes
0 answers
14 views

MC condition in Cellular Potts Model

In the following discussion, Introduction to the CPM I haven't understood the following MC condition: Note the "try" in the previous sentence; this so-called "copy attempt" only ...
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0 votes
1 answer
24 views

Would it be possible to design a dart-like object such that it survives re-entry and impact at interplanetary / interstellar speeds?

I was wondering about spacecraft - specifically just getting from point A to B. If you were unconcerned about human survival and damage from g-forces, it would be much easier to deliver it without the ...
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  • 11
0 votes
0 answers
7 views

Is there a limit to the number of superconductors than can be flux pinned to a single magnetic source?

Is some quantity of magnetic flux consumed(or redirected(just not available in the free space around the magnet)) to flux pin a superconductor. I.E. If you have 2 superconductors can you place them on ...
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