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15075 | Is time the property of an object? | I don't know if the title makes much sense, but hopefully it will become clear with the text. Temperature is not a property of a point in the three dimensions, but actually of the object occupying that point. Similarly, is time the property of the point in three dimensions or of the object occupying it? If time is the ... | In the context of special relativity, if one twin travels at a significant fraction of the speed of light while the other remains on Earth, how much younger will the traveling twin be when they reunite, assuming they spent 10 years on Earth according to the stay-at-home twin? | 20,435 | cqadupstack-physics |
24981 | Why are there more lunar maria on the near side than on the far side? | It is widely known that the side of the moon that faces us has a particularly large number of dark patches, which resemble seas of liquid, hence, "maria". It is strange, though, that the far side of the moon has a great lack of these features. Why does the far side of the moon have so few maria? If they maria formed du... | What is the primary reason for the significant difference in the number of maria between the near side and far side of the moon, and how does this relate to the historical impact rate experienced by each side? | 5,049 | cqadupstack-physics |
103955 | What are the restrictions on the Hamiltonian in QM? | In quantum mechanics, we usually write the Hamiltonian as: $$\hat{H}=\hat{T}+\hat{V}$$ But in classical mechanics, there are several reasons why it **would not have this form** : * We've chosen some particular coordinate system where there is no conservation of energy (we're neglecting the source of external forces).... | What are the conditions under which the Hamiltonian operator in quantum mechanics must be self-adjoint and bounded from below, and how do these conditions relate to the physical interpretation of energy eigenvalues? | 22,956 | cqadupstack-physics |
122988 | Why a transistor is activated when I touch its base with my finger? | Is my body charged eletrically? If so, how much? Will it work with all types of transistors? | What is the typical electrical charge of a human body in microcoulombs, and how does this charge affect the operation of various types of transistors? | 35,664 | cqadupstack-physics |
11293 | Determining wave function for term symbol 1D | I am trying to follow a book (Introduction to Ligand Field Theory by Ballhausen in 1962 on pg 15), but it isn't clear how they make a particular leap. **Background** I want to find the wave function for the term $^1 D$. We know that $\psi(L,M_L,S,M_S) = \psi (2,2,0,0)$ is made up of three micro states: $(2^+,0^-)$, $(2... | How do you derive the conditions \( a \sqrt{3} - b \sqrt{3} + c \sqrt{8} = 0 \) and \( a + b = 0 \) when expressing the wave function \( \psi(2,2,0,0) \) as a linear combination of the microstates \( (2^+,0^-) \), \( (2^-,0^+) \), and \( (1^+,1^-) \), and what does the presence of the square root terms signify in relat... | 35,264 | cqadupstack-physics |
3703 | What's the difference between an entangled state, a superposed state and a cat state? | 1) Can a state be entangled without also being a superposition? (Please give an example.) 2) Can a state be a superposition without being entangled? (Again, an example please.) 3) And what about a cat state? I am royally confused, and a little bit of googling didn't help. This question is partly motivated by the rece... | Consider a two-qubit system where one qubit is in the state \( |0\rangle \) and the other is in the state \( |+\rangle = \frac{1}{\sqrt{2}} (|0\rangle + |1\rangle) \).
1) Is this two-qubit state entangled? Justify your answer mathematically.
2) Is this state also in superposition? Explain why or why not with appropr... | 29,331 | cqadupstack-physics |
55194 | Why can't we accelerate to the speed of light? | Why can't we accelerate to the speed of light? It's just a speed and nothing else. Universe also crossed the speed of light at the time of big bang. Is this is just a interpretation or there is any fact behind it? I am asking it as I don't know much about this theory. | What is the relativistic kinetic energy of an object with a mass of 1 kg as it approaches 99% the speed of light, and how does this compare to its energy at rest? | 32,333 | cqadupstack-physics |
110320 | Does divergence of Taylor series for relativistic $E(p)$ for $p\ge m$ have any physical significance? | When one wants to include weak relativistic effects in classical equations, usually kinetic energy term is expanded into Taylor series about $p=0$. But the complete dispersion relation is $E=\sqrt{m^2+p^2}$, which has branch points at $p=\pm im$, thus its Taylor series diverges for any $p: |p|\ge m$. Does such divergen... | What are the implications of the divergence of the Taylor series expansion of the energy-momentum relation \( E = \sqrt{m^2 + p^2} \) at momentum values \( |p| \geq m \), particularly regarding the physical phenomena of pair production or annihilation? | 19,122 | cqadupstack-physics |
56432 | Determine viscosity using falling sphere (Stokes Law, Ladenburg correction) | ## Introduction I am trying to determine the viscosity of a fluid. Therefore, I let a sphere of known mass `m` and radius `r` fall (sink) into the fluid. I then measure the time it takes to sink/travel a given height. Then there are the following forces having a effect on the sphere: $F_g = mg$ and $F_a = \frac{4 \rho ... | How can I determine the viscosity of a fluid using the sinking motion of a sphere, taking into account the Ladenburg correction factor, and why is it necessary to extrapolate the viscosity values obtained from spheres of varying radii to a radius of 0 mm? | 15,875 | cqadupstack-physics |
99673 | how electrophoretic display like E ink retains particles on top of capsule without power? | how electronic ink display retains the particles on top of micro capsule when charge on electrode is released or when device is powered off? Doesnt that make particles loose on the dielectric fluid on capsule after volatge on electrode is removed? How e ink maintains image even when device is powered off? I have unders... | How does electronic ink technology manage to maintain the position of charged particles within microcapsules in a dielectric fluid when the voltage on the electrode is removed, allowing the display to retain an image even after the device is powered off? | 13,302 | cqadupstack-physics |
134412 | Can the term «shadow» pertain to anything else than light? | Can the term shadow pertain to anything else than light? Feel free to interpret this question in the widest sense possible. | In terms of quantum physics, can a "shadow" be defined in relation to particles other than photons? If so, provide a specific example and explain the conditions under which this "shadow" would manifest. | 19,220 | cqadupstack-physics |
101984 | How does a complex wavefunction "hold" energy? | Feynmann Lectures Vol 3 Ch 8 Sec 6 describes how an ammonia molecule can have two definite energy states. If the amplitudes of the base states are $ C_1(t) =\frac{a}{2}\,e^{-(i/\hbar)(E_0-A)t}+\frac{b}{2}\,e^{-(i/\hbar)(E_0+A)t}$ $C_2(t) =\frac{a}{2}\,e^{-(i/\hbar)(E_0-A)t}-\frac{b}{2}\,e^{-(i/\hbar)(E_0+A)t}$ then you... | In the context of quantum mechanics and the ammonia molecule described by the amplitude equations \( C_1(t) \) and \( C_2(t) \), if you set \( a=0 \) or \( b=0 \) for definiteness in energy states, what are the corresponding physical conditions or factors that justify these choices? Additionally, how does the energy as... | 15,733 | cqadupstack-physics |
6209 | Paradoxical interaction between a massive charged sphere and a point charge | Suppose we have a sphere of radius $r$ and mass m and a negatively charged test particle at distance d from its center, $d\gg r$. If the sphere is electrically neutral, the particle will fall toward the sphere because of gravity. As we deposit electrons on the surface of the sphere, the Coulomb force will overcome grav... | What physical principles or constraints could explain why the gravitational attraction on the test particle does not continue to increase indefinitely with the addition of electrons to the sphere, leading to the particle eventually accelerating away from the sphere? | 22,166 | cqadupstack-physics |
33212 | Reflectance of Titanium as Function of Thin Film Thickness | As far as I know, transmittance equals $e^{-\alpha x}$, where $\alpha$ is absorption coefficient and $x$ is thin film thickness($100-300\,nm$). My team and I have engineered a way to find absorption. Transmittance, T= (Output intensity)/(initial intensity). And, absorption A=(initial intensity-output intensity)/(initia... | What is the equation for the reflectance of titanium (Ti) as a function of thin film thickness at a wavelength of 808 nm, taking into account both transmittance and absorption effects? | 31,003 | cqadupstack-physics |
77250 | Where to find information about rocket launches (speed, height, trajectory)? | 1. I want to find experimental data from real launches, with some description of a rocket like full mass, fuel mass, thrust and so on. Just trying to model it. 2. Where to read about precise methods of calculating air resistance for rockets. | Can you provide a detailed example of a rocket launch, including the full mass, fuel mass, thrust, and any relevant experimental data? Additionally, what are the precise methods used to calculate air resistance for rockets, and how do these factors affect a rocket's trajectory? | 17,588 | cqadupstack-physics |
15906 | Relative Synchronicity | Einstein said that the synchronization of two clocks is dependant on the velocity of the observer. But I feel a conceptual contradiction can be made: There are two observers A and B. Observer 'A' faces direction X, and will be labeled "stationary." Another observer B faces direction X and is travelling rapidly in that ... | How does the synchronization of clocks differ for two observers, one stationary and one moving at relativistic speed, when their clocks are arranged in different orientations relative to their motion, according to the principles of special relativity? | 20,912 | cqadupstack-physics |
116853 | Are diffeomorphisms a proper subgroup of conformal transformations? | The title sums it pretty much. Are all diffeomorphism transformations also conformal transformations? If the answer is that they are not, what are called the set of diffeomorphisms that are not conformal? General Relativity is invariant under diffeomorphisms, but it certainly is not invariant under conformal transforma... | Are all diffeomorphisms also conformal transformations in the context of General Relativity, and if not, what is the name of the set of diffeomorphisms that do not preserve angles? | 19,560 | cqadupstack-physics |
94522 | A change of units in Bethe formula | I'm reading through the following paper: _Monte Carlo simulation of non relativistic electron scattering_ by W. Williamson and G. C. Duncan. In the following paragraph, I want to know how to arrive at $(2)$ from $(1)$. (It's basically a change of units) : > Bethe has derived an expression which gives the kinetic energy... | What is the numerical coefficient of the energy loss per unit path length, given in units of \(\frac{\mathrm{keV}}{\mu\mathrm{m}}\), when converting the Bethe formula from CGS to SI units, and how do you derive this coefficient using the values of \(e\), \(N\), and the constants involved? | 36,941 | cqadupstack-physics |
76239 | Question about "quadrupole radiation" vector potential formula derivation | I tried to get an expression for $\mathbf A (\mathbf x )$ in quadrupole approximation. After some transformations of Liénard–Wiechert vector potential I got, as in many books, $$ \mathbf A \approx \frac{1}{c|\mathbf x|}\int \mathbf j (\mathbf r , T)d^{3}\mathbf r + \frac{1}{c^{2}|\mathbf x|}\partial_{T}\int \mathbf j (... | In the quadrupole approximation for the vector potential \(\mathbf A\), the correct expression includes a term proportional to the second time derivative of the quadrupole moment tensor \(Q^{\alpha \beta}\). Given the mistake identified in the derivation, can you calculate the correct prefactor for the term involving \... | 2,268 | cqadupstack-physics |
130219 | The Gluon - Does It Exhibit Wave Properties? | Do Gluons have frequencies and wavelengths? I assume that they do, but have been unable to find anything on point in SE or Wikipedia. Just beginning to study university-level physics here. | What are the characteristic frequencies and wavelengths associated with gluons, and how do these relate to their properties as gauge bosons in the context of quantum chromodynamics? | 38,222 | cqadupstack-physics |
99252 | Meaning of kinetic part in the Lagrangian density? | What is the **physical meaning** of the kinetic term in the classical scalar field Lagrangian $$\mathcal{L}_{kin}~=~\frac{1}{2}(\partial_\mu\phi)(\partial^\mu\phi)~?$$ It gives how does the field change from one space-time point to the other. Right? What is the significance of the relative minus sign between the square... | What is the significance of the relative minus sign in the kinetic term of the classical scalar field Lagrangian $$\mathcal{L}_{kin} = \frac{1}{2}(\partial_\mu\phi)(\partial^\mu\phi)$$ when comparing the contributions from the time gradient and the spatial gradient? How does this affect the stability and propagation of... | 34,670 | cqadupstack-physics |
23572 | How does an object regains its neutrality after being charged by rubbing? | Objects (like comb) can be charged by rubbing as charged particles, particularly electrons, are transferred from one object to other. This can be seen as the object (comb) attracts small bits of paper. After some time, the charge on the body seems to disappear. How does this charge disappear without any external influe... | What mechanisms explain the apparent disappearance of charge from a comb after it has been rubbed to become charged, and what role do environmental factors such as humidity play in this process? | 32,675 | cqadupstack-physics |
83649 | How to find the Stress-Energy tensor? | I am a bit at loss about how to proceed to find the stress-energy tensor given some distribution of matter. The Wikipedia page gives some examples, and some (inequivalent) definitions for it: * Using the Einstein-Hilbert action we get the Hilbert stress-energy tensor $$T^{\mu\nu} = \frac{2}{\sqrt{-g}}\frac{\delta (\m... | Given a distribution of matter in a curved spacetime, how can one derive the matter Lagrangian \(\mathcal{L}_\mathrm{matter}\) if the Hilbert stress-energy tensor \(T^{\mu\nu}\) is defined as \(T^{\mu\nu} = 2 \frac{\delta \mathcal{L}_\mathrm{matter}}{\delta g_{\mu\nu}} + g^{\mu\nu} \mathcal{L}_\mathrm{matter}\)? Please... | 32,366 | cqadupstack-physics |
131846 | Researching an automobile accident.Wondering if someone can help me as I never studied physics | I am trying do some independent research on a recent auto collision where the information released doesn't seem plausible based on the pictures that I have seen of the accidents aftermath. A 5,500lb(2500kg) vehicle, referred to as "A", with a stated speed of 68mph strikes a vehicle, referred to as "B", weighing 2,657lb... | What would be the approximate change in momentum for vehicles A and B during their collision, given their weights and speeds before the impact? | 16,307 | cqadupstack-physics |
105413 | Why is there no massless spin 1/2 particles with charge? Is there any underlying theory? | Whether any massless spin 1/2 particles cannot have charge? If so, why? | What is the theoretical relationship between the mass, charge, and spin of fundamental particles, specifically considering massless spin 1/2 particles? Can you provide an example of such a particle and explain why it may or may not possess charge? | 33,591 | cqadupstack-physics |
41221 | Does the nonlocality of the preferred basis mean QM is nonlocal? | Take the Mach-Zehnder interferometer as an example. A photon passes through a beam splitter, is reflected off mirrors, and interferes with itself at another half-silvered mirror. No measurements or disturbances are made in between. The preferred basis of the photon is given by which path it takes after passing the seco... | In a Mach-Zehnder interferometer, if a photon takes one of the two paths and the probability amplitude for each path is given as \( \alpha \) and \( \beta \), calculate the overall probability of detecting the photon at the output beam splitter given that the visibility of the interference pattern is \( V = \frac{|\alp... | 26,142 | cqadupstack-physics |
17904 | Space expansion effect on wavelengths across two points in space | Is the expansion of space taken into consideration when calculating light or any (Radio to Gamma) wave length distance and speed? I know C is a constant, but my concern is if "space expansion" is somehow altering the speed of light or any other wave length relative between two points. | How does the expansion of space affect the measured wavelength and speed of light or other electromagnetic waves when calculating distances between two points in the universe? | 16,381 | cqadupstack-physics |
1908 | Buckyballs in vacuum | I've read about the idea that buckyballs and other nanostructures could be used to hold drugs and things until they reach certain places in the body and then get released. So I was wondering, if you created a buckyball in air, so that some molecules that are in air (such as oxygen and nitrogen) were inside the buckybal... | If a buckyball contains air molecules, such as oxygen and nitrogen, and is then placed in a vacuum, what will happen to the air molecules inside the buckyball? Will they escape, or remain trapped? Additionally, if a buckyball is formed in a vacuum and then exposed to atmospheric pressure, will any molecules from the at... | 29,850 | cqadupstack-physics |
75864 | silicon oxide - aluminium interface voltage | Let us consider a MOS (metal oxide semiconductor FET) system. Now the threshold voltage of aluminium of the gate of such a FET of 4.1 eV and that of the silicon oxide layer is different. My book claims that due to the threshold voltage difference, a voltage difference is created which is termed as the **built in voltag... | What is the built-in voltage for a MOSFET with an aluminum gate exhibiting a threshold voltage of 4.1 eV and a silicon oxide layer with a threshold voltage of 3.2 eV? Provide the calculation and explanation for the difference. | 19,452 | cqadupstack-physics |
7132 | What is the possible potential? | The professor asked us to do this one: "..Determine all potentials $V(r,\theta, \phi)$ for which it is possible for find solutions of the time independent Schrodinger equation which are also eigenfunctions of the operator $L_{z}$." I try to solve this problem by assuming separation of variables, and I get $$\Phi(r,\the... | What specific forms of the potential \( V(r,\theta,\phi) \) satisfy the condition that the commutator \( [L_{z}, V(r,\theta,\phi)] = 0 \) and allow for solutions of the time-independent Schrödinger equation that are also eigenfunctions of the operator \( L_{z} \)? | 594 | cqadupstack-physics |
82564 | What limits range of gravitational attraction concerning space expansion? | Wikipedia says: > Metric expansion is a key feature of Big Bang cosmology and is modeled > mathematically with the FLRW metric. This model is valid in the present era > only on large scales (roughly the scale of galaxy clusters and above). At > smaller scales matter has become bound together under the influence of > gr... | What is the approximate physical scale at which gravitational binding forces become significant enough to counteract metric expansion in the universe, and how does this relate to the separation between gravitationally bound systems like galaxy clusters and the expanding universe? | 16,362 | cqadupstack-physics |
95627 | Can a mass matrix be asymmetric? | I am developing a mathematical model of a mechanical device consisting basically of coupled harmonic oscillators. It turns out that the system mass matrix is asymmetric. I seem to read somewhere that a mass matrix has to be symmetric, but I am not sure. So I would like to know whether it is possible for a mass matrix i... | Is it possible for the mass matrix of a system of coupled harmonic oscillators to be asymmetric, and if so, what are the physical implications of such a matrix in the context of the mechanical oscillators? | 11,712 | cqadupstack-physics |
99373 | The effect of high frequency AC current in a fresh corpse | 1. Given two AC currents of the same intensity, eg 20 mA, but different frequency, 60 Hz and 20MHz, which one would be more likely to reach the heart ? 2. I've read about the skin effect and how current tends to flow on the surface of a conductor. Does that apply to a dead human body at this particular context? 3.... | Given two AC currents with the same intensity of 20 mA but different frequencies—one at 60 Hz and the other at 20 MHz—determine which current is more likely to penetrate a dead human body and reach the heart, considering the skin effect and its implications on current flow at these frequencies. | 25,782 | cqadupstack-physics |
110169 | What does "optical conductivity" mean? | Does it just mean "AC electric conductivity"? If so, why have a special name for it, and why mention optical specifically? The wikipedia page on it is very sparse. This (warning, PDF) document just says: > The term “optical conductivity” means the electrical conductivity in the > presence of an alternating electric fie... | What is the relationship between optical conductivity and AC conductivity, and how do their definitions differ in the context of materials exposed to an alternating electric field? | 27,504 | cqadupstack-physics |
92484 | Equation for Hubble Value as a function of time | I am trying to write the equation for the situation where the Hubble parameter $H$ would be changing over time. In other words, it would represent an accelerated expansion of the Universe. That is, $H$ can no longer be the simple $H=1/t$. In the new equation, I should be able to plug a future time and see what the Hubb... | Given the equation for the scale factor in a flat universe, \( a(t) = a_0 t^{2/3(w+1)} \), determine the Hubble parameter \( H \) as a function of time \( t \) for different values of the equation of state parameter \( w \), specifically for \( w = -0.9 \) and \( w = -1.1 \). What does this imply about the nature of co... | 37,173 | cqadupstack-physics |
10240 | Is the wave function objective or subjective? | Here is a question I am curious about. Is the wave function objective or subjective, or is such a question meaningless? Conventionally, subjectivity is as follows: if a quantity is subjective then it is possible for two different people to legitimately give it different values. For example, in Bayesian probability theo... | If two scientists, A and B, have different wave functions for the same quantum system based on their distinct sets of information, what conditions would determine whether one wave function is objectively correct and the other is not? | 35,711 | cqadupstack-physics |
88510 | Fluid Mechanics Piston Problem |  **The actual problem:** A hydraulic car lift has a reservoir of fluid connected to two cylindrical fluid filled pipes. The pipe directly below the car has a diameter of 1.8 m. the pipe on which the plunger acts has a diameter of 0.045m. the plunger is ... | If a hydraulic car lift has a large cylindrical pipe with a diameter of 1.8 m and a smaller pipe with a diameter of 0.045 m, and the plunger in the smaller pipe is depressed by 1.5 m, how high does the car rise in the larger pipe? Show your calculations. | 23,536 | cqadupstack-physics |
129594 | Why did the Homestake experiment only detect solar neutrinos? | The Homestake experiment was designed to detect solar neutrinos. In order to shield it from the background, it was set up in a deep underground mine. It was found that the only one third of expected neutrinos were detected, leading to the solar neutrino problem. What I wonder is why neutrinos created in the upper atmos... | What percentage of solar neutrinos detected in the Homestake experiment were consistent with the expected values, and what implications does this have for our understanding of neutrino interactions and the solar neutrino problem? | 13,623 | cqadupstack-physics |
39166 | Torque and equilibrium | I am a little stuck on the concept involved in part b) of the following problem: A $5 m$ long road gate has a mass of $m = 15 kg$. The mass is evenly distributed in the gate. The gate is supported at point A by a rod attached to the ground below the gate. Point A is located $20 cm$ from the left end. The gate rotates a... | What is the minimum downward force that needs to be applied at the right end of a $5 m$ long road gate, which has a mass of $15 kg$ evenly distributed and is supported at one end close to the left and another at the right, in order to eliminate the support force at the left end? | 33,717 | cqadupstack-physics |
35875 | Validity of Cutkosky cutting rules for fermions | It is rather obvious for me that the generalized optical theorem (see e.g. Peskin&Schroeder) must hold for S-matrix elements for fermions as it is directly related to the unitarity of the S-matrix. But what about the generalization by Cutkosky to individual Feynman graphs? Do Cutkosky rules hold for any Feynman graph i... | Do the Cutkosky rules apply to all Feynman graphs in arbitrary perturbative quantum field theory, and do these rules have a consistent form across different types of fields, such as fermions and scalars? Additionally, how do these rules change when considering finite temperature field theory? | 16,761 | cqadupstack-physics |
88837 | Difference in perception of unpolarized and polarized light | What is the difference in perception of polarized light and unpolarized light? What difference does polarized light cause to our eyes? | How does the transmission of polarized light through a polarizing filter differ from that of unpolarized light, and what quantifiable effects can this have on visual perception in terms of brightness and contrast? | 9,131 | cqadupstack-physics |
46148 | One strategy in a snowball fight | Here's a common college physics problem: > One strategy in a snowball fight is to throw a first snowball at a high > angle over level ground. While your opponent is watching the first one, you > throw a second one at a low angle and timed to arrive at your opponent > before or at the same time as the first one. Assume ... | In a snowball fight, if you throw the first snowball at an angle of 70.0° with an initial speed of 25.0 m/s, what should be the angle of the second snowball thrown at the same speed in order to land at the same point? Additionally, how many seconds later should the second snowball be thrown to ensure both arrive at tha... | 5,153 | cqadupstack-physics |
50131 | Trying to understand "recursion at the lowest level of matter" | I'm reading the book Gödel, Escher, Bach: an Eternal Golden Braid and on Chapter V, Hofstadter talks about different examples of recursive structures and processes. By page 142 of the 20th anniversary edition, he starts talking about recursion at the lowest level of matter, that is, according to him, related to the str... | What is the mathematical expression that describes the simplest path of an electron propagating from point A to point B in a theoretical world without external interactions, and how can this concept be related to the Feynman diagrams used in quantum mechanics? | 221 | cqadupstack-physics |
79887 | Is special relativity axiomatic? | Can special relativity be somewhat described by the following statement? > _If the speed of light is a universal constant, and if light can be placed > in separate frames of motion, then time must be altered by speed._ | If the speed of light in a vacuum is approximately \(3 \times 10^8\) meters per second, and a spaceship travels at \(0.8c\) (where \(c\) is the speed of light), how much time would elapse on the spaceship for a journey that takes 10 years from the perspective of an observer on Earth? | 32,544 | cqadupstack-physics |
12235 | Iterated dimensional regularization | Given a 2-loop divergent integral $\int F(q,p)\,\mathrm{d}p\mathrm{d}q$, can it be solved iteratively? I mean 1. I integrate over $p$ keeping $q$ constant 2. Then I integrate over $q$ In both iterated integrals I use dimensional regularization. Can it be solved iteratively? I presented a paper to a teacher of mine ... | Can the two-loop integral \( \iint dp\,dq\, F(q,p)(p+a)^{-s}(q+a)^{-s} \) be regularized using the method I proposed by introducing regulators for each variable, and can the integration be performed iteratively while ensuring the total value remains finite? What steps would be necessary to validate this approach? | 29,462 | cqadupstack-physics |
93537 | $\mathcal{N}=4$ SUSY in $d=3$ versus $\mathcal{N}=2$ in $d=4$ | Which is the field content of the hypermultiplet and the vector multiplet in $\mathcal{N}=4 \ d=3$ Supersymmmetry? Is it correct to state that $\mathcal{N}=4$ in $d=3$ has $8$ supercharges, (since there are $4$ minimum dimension spinors, and the lowest dimensional representation of $SO(1,2)$ has real dimension 2), is c... | What are the differences in field content between the hypermultiplet and vector multiplet in $\mathcal{N}=4 \ d=3$ Supersymmetry, and can you explain how the supercharges compare between $\mathcal{N}=4 \ d=3$ and $\mathcal{N}=2 \ d=4$? | 22,829 | cqadupstack-physics |
129310 | Symmetric eigenfunctions? | So a symmetric eigenfunction / wavefunction is defined as: $$P_{ij} ψ_a (r_1,r_2,…,r_i,…,r_j,…,r_N )=ψ_a(r_1,r_2,…,r_i,…,r_j,…,r_N )$$ But for it to be symmetric does this have to be true for all $ij$ combinations or only one? (note that $P_{ij}$ is the exchanges the element $r_i$ for $r_j$) | In the context of quantum mechanics, consider a wavefunction \( \psi_a(r_1, r_2, \ldots, r_N) \) of \( N \) identical particles. If the wavefunction is defined to be symmetric under the exchange of any two particles \( r_i \) and \( r_j \), denoted by the operator \( P_{ij} \), how many pairwise exchange conditions mus... | 32,660 | cqadupstack-physics |
89187 | What is the experimental status of the G2-MSSM? | The G2-MSSM is supposed to be the low-energy theory of a hypothetical class of M-theory compactifications studied by some phenomenologists. It is just the MSSM, but in a particular region of parameter space. The high-energy theory is M-theory compactified on a manifold with G2 holonomy. The MSSM fields come from a spec... | What is the predicted range for the Higgs boson mass according to the G2-MSSM, and how does this prediction compare to experimental measurements from the LHC? | 1,418 | cqadupstack-physics |
62094 | Energy Gain with capacitor? | I have a question about energy gain in capacitors. Assume the following system:  As the electron gets accelerated inside the capacitor, it will have more kinetic energy coming out than going in. But the capacitor has not lost any energy. Where is the energy coming from... | If an electron is accelerated between two parallel capacitor plates with a potential difference \( V \) in a vacuum, calculate the increase in kinetic energy of the electron as it moves from the negative plate to the positive plate. Assume the mass of the electron is \( 9.11 \times 10^{-31} \) kg and the charge is \( -... | 4,489 | cqadupstack-physics |
32596 | How did Cook and other astronomers time the 1769 Venus transit? | The 1769 transit of Venus was observed and coordinated by over one hundred astronomers around the world. How did they measure time so accurately, key to the observations having any scientific value? I find little information online regarding 18th century timekeeping devices. I assume that they were mostly using clocks ... | What were the timekeeping devices used by astronomers during the 1769 transit of Venus, and how did their accuracy compare to modern standards? | 27,106 | cqadupstack-physics |
69163 | Einstein action as a functional of the tetrad (first order formulation of gravity) | Let the Einstein-Hilbert action be rewritten as a functional of the tetrad $e$ (units shall be set to $1$) such that $S_{EH}(e)=\int \frac{1}{2}\epsilon_{IJKL}~e^I\wedge e^J\wedge F^{KL}(\omega(e))$, where $\epsilon$ is the Levi-Civta-symbol as usual, $F$ is the curvature of the spin connection $\omega$ and $I,J,K,L$ d... | How can I derive the Einstein-Hilbert action in the form \( S_{EH}(g)=\int d^4x \sqrt{-g} R \) starting from the expression \( S_{EH}(e)=\int \frac{1}{2} \epsilon_{IJKL} e^I\wedge e^J\wedge F^{KL}(\omega(e)) \), and what identities or mathematical steps should I use in the process? | 29,464 | cqadupstack-physics |
20883 | How is the apparent significance of (length) scales in physics explained? | From what I understand, especially from reading arguments on Physics.SE, different (length) scales of a system are extremely important. It's clear that if there are two scales $\delta,d,D,\Delta$ with say $$\delta < d \ll D < \Delta,$$ then effect, which happen on a length scale $d$ might be neglected if one is interes... | Consider a physical system characterized by three different length scales: a small scale \(d\), a medium scale \(\delta\), and a large scale \(D\), such that \(\delta < d \ll D\). If a certain physical effect is observed at the scale \(D\), how would you determine whether the effects at the medium scale \(d\) can be ne... | 5,746 | cqadupstack-physics |
61299 | Proof for angar speed equation | I'm struggling to find a solution to a project for college. I have looked through my textbook countless times and googled for days, but I just can't seem to figure it out. The question is that we need to prove the angular speed of a hanging rotating weight is given by the expression: W = root(g/Lcos.theta) Please can y... | Prove that the angular speed \( \omega \) of a hanging rotating weight can be expressed as \( \omega = \sqrt{\frac{g}{L \cos \theta}} \), where \( g \) is the acceleration due to gravity, \( L \) is the length of the string, and \( \theta \) is the angle of displacement from the vertical. What assumptions need to be ma... | 3,508 | cqadupstack-physics |
34809 | Do arXiv links last for the forseeable future? | If I give someone an arXiv link, say http://arxiv.org/abs/0707.0118 , will this link last for the foreseeable future? | What is the estimated lifespan of a digital link, such as one from arXiv, based on internet archival practices and the stability of digital resources? | 34,302 | cqadupstack-physics |
106253 | Is there a handwavy way to explain what quantum correlation means? | Is there a simple way to explain the difference between a classical and truly quantum correlation to a non-quantum person who has basic understanding classical correlation? I mean without invoking quantum mechanics, a simple CHSH type Bell inequity can be explained without it--perhaps with a little more math than I'm l... | What is the maximum value of the correlation coefficient for classical correlations in a CHSH-type experiment, and how does it differ from the maximum value achievable in a quantum correlation scenario? | 25,153 | cqadupstack-physics |
7218 | How can there be net linear momentum in a static electromagnetic field (not propagating)? | I understand from basic conservation of energy and momentum considerations, it is clear in classical electrodynamics that the fields should be able to have energy and momentum. This leads to the usual Poynting vector and energy density relations for electromagnetic fields. However, I do not know how to interpret situat... | In the scenario where two magnetic dipoles are arranged along a massless string, one oriented in the -z direction at the origin and the other in the +z direction at y=+L, how can we explain the presence of a net linear momentum in the static electromagnetic field calculated as \(p_{em} = m q \frac{\mu_0}{2 \pi L^2} \ha... | 81 | cqadupstack-physics |
31923 | Naive Question About Batteries | I do apologize for the ignorance that I'm sure is imbedded in this question, but I'd like to understand the exact point at which the following argument goes wrong: 1) A battery (let's say an ordinary flashlight battery) maintains a voltage between its positive and negative terminals. 2) The only way to maintain a volta... | What is the charge distribution on a typical flashlight battery, and why doesn’t it produce a net charge sufficient to attract objects like a paper clip? | 8,978 | cqadupstack-physics |
31077 | Man on treadmill and energy/mass conservation | Suppose we put a very obese man inside a large air tight isolated room with a treadmill and he runs on the treadmill for 24 hours and at the end of the day he sees his weight has come down (mostly water weight, but also includes some fat), would the weight of the entire sealed room be decreased? | If a very obese man runs on a treadmill in a sealed airtight room for 24 hours and loses weight predominantly through water loss and fat burning, what would be the overall change in weight of the entire sealed room, considering the principles of conservation of mass and energy? | 11,049 | cqadupstack-physics |
5149 | What is the status of applying numerical analysis to QM/QFT problems | This is something I don't ever seem to hear about, except regarding QCD ("lattice QCD"). What about QED? Is numerical integration always inferior to hand-calculating Feynman diagrams in perturbation theory? What about numerical simulation of the full time-evolution of a quantum field (rather than just calculating corre... | What is the estimated computational power required to numerically simulate the time evolution of quantum electrodynamics (QED) at a precision comparable to the analytic calculations of physical quantities, such as the anomalous magnetic moment of the electron? | 15,698 | cqadupstack-physics |
28221 | Dirac's quantization rule | I first recall the Dirac's quantization rule, derived under the hypothesis that there would exit somewhere a magnetic charge: $\frac{gq}{4\pi} = \frac{n\hbar}{2} $ with $n$ natural. I am wondering how the quantization of electric charge can be deduced from it. The quantization of the product $gq$ is certainly not enoug... | Given Dirac's quantization rule, \(\frac{gq}{4\pi} = \frac{n\hbar}{2}\), where \(g\) is the magnetic charge, \(q\) is the electric charge, \(\hbar\) is the reduced Planck's constant, and \(n\) is a natural number, how can the quantization of electric charge \(q\) be derived? What conditions or additional factors are ne... | 34,681 | cqadupstack-physics |
96045 | Idea of Covering Group | 1. $SU(2)$ is the covering group of $SO(3)$. What does it mean and does it have a physical consequence? 2. I heard that this fact is related to the description of bosons and fermions. But how does it follow from the fact that $SU(2)$ is the double cover of $SO(3)$? | What is the number of distinct quantum states for a spin-1/2 particle, and how does this relate to the double covering relationship between $SU(2)$ and $SO(3)$? | 16,943 | cqadupstack-physics |
49789 | Examples of systems with energy as an intensive variable | I need to consider a couple of examples of systems which have energies that are intensive variables - not extensive. I'be been thinking about this and I am not coming up with anything. My understanding is that extensive variables (at least wrt usual energies) scales with mass or length (system size). It also seems that... | What are two examples of intensive energy variables in physical systems, and how do they differ from extensive energy variables? | 27,517 | cqadupstack-physics |
74605 | What kind of physics topics exist? | The question says everything I want to know, but for more details: I enjoy studying physics but the problem is that I can't find any information with a summary of all physics topics, collected together. I also Googled this and took a look at other websites and searched this website but without success. So if someone kn... | What are the major topics covered in the field of physics, from basic concepts to advanced theories, and is there a comprehensive book similar to the _Princeton Companion to Mathematics_ that outlines these topics? | 19,679 | cqadupstack-physics |
112804 | Form factor and average value | Why Our Electricity Flowing in the Sequence of 11kv,33,66,132kv,why not Flow in 10 kv,11,12,13,14 that Sequence. | What are the advantages of using standardized voltage levels such as 11 kV, 33 kV, and 132 kV in electrical power transmission systems instead of a continuous range like 10 kV, 11 kV, 12 kV, etc.? | 9,822 | cqadupstack-physics |
77271 | Explanation for the minus sign in $\Omega_3$ in the Kappa symmetry of the Green - Schwarz formalism for F1 strings | > _Just so that there can be more higher - level physics questions here, let > me post this question + answer. Also because I'm a bit sad that there are > almost no questions on the Green-Schwarz formalism._ In the Green-Schwarz formalism, for F1 strings, we have the action $$S=S_1+S_2$$ Where $${S_1} = - T\int_{}^{} {... | What is the significance of the minus sign in the expression for the 3-form \(\Omega_3 = A\left( {{\text{d}}{{\bar \Theta }^1}{\gamma _\mu }{\text{d}}{\Theta ^1} - {\text{d}}{{\bar \Theta }^2}{\gamma _\mu }{\text{d}}{\Theta ^2}} \right){\Pi ^\mu }\), and how does it relate to the chiral nature of Type IIA String Theory... | 3,590 | cqadupstack-physics |
61335 | Show that the plane of incidence is perpendicular to the surface of reflection | Is it possible to derive from the boundary conditions of the Maxwell equations for E and H, that the plane of incidence for an EM wave is perpendicular to the reflection surface? How? If not, what additional condition is needed? | Can you derive the relationship between the plane of incidence and the reflection surface for an electromagnetic wave using the boundary conditions of Maxwell's equations for the electric field (E) and magnetic field (H)? If you find it impossible, what specific additional condition must be included? | 12,652 | cqadupstack-physics |
132500 | How to find tension in the cantilever brakes? |  In the left side example of cantilever brakes, how do I find the tension in strings DE and DC, in terms of T. According to me applying force balance equations, horizontal and vertical forces should be zero i.e. $T_{DE} \cos(45) + T_{DE} \cos(45) = T$..... | In a cantilever brake system with two strings DE and DC making an angle of 45 degrees with the horizontal, if a force T is applied, what are the tensions in strings DE and DC in terms of T? Explain your reasoning using force balance equations. | 10,824 | cqadupstack-physics |
89237 | Capacitors in parallel and capacitors in series | How can I recognize clearly when I deal with capacitors in parallel or capacitors in series? Can follow a "rule" or a intuitive method? I have to do difficult exercises regarding system of capacitors so I must understand when I have capacitors in parallel or in series. Can you explain me in a simple way? | In a circuit containing three capacitors with capacitances of 2 µF, 4 µF, and 6 µF, if the 2 µF and 4 µF capacitors are connected in series and their combination is then connected in parallel with the 6 µF capacitor, what is the total equivalent capacitance of the circuit? | 6,322 | cqadupstack-physics |
70641 | Understanding Charles's Law | Charles's law states that, > The volume of a given mass of an ideal gas is directly proportional to its > temperature on the absolute temperature scale (in Kelvin) if _pressure_ and > the amount of gas remain constant; that is, the volume of the gas increases > or decreases by the same factor as its temperature. Which ... | In a closed container with a movable piston, if the volume of an ideal gas is directly proportional to its temperature according to Charles's law, how would the pressure inside the container change if the temperature is increased while keeping the outside pressure constant? Calculate the new pressure if the initial pre... | 33,393 | cqadupstack-physics |
79220 | How do the effects of semiconductor doping affect the Hall effect? | For instance, consider number 4 and 5 in the following sample:  Using the right hand rule, B points downwards, conventional current points to the right (because of the 5V battery), and therefore, the force on electrons points into the page. Electrons ar... | If the conventional current in a semiconductor setup is flowing from a ground (0 V) point to a higher voltage point (5 V) and is shown to read a negative value on the voltmeter, what is the resultant electric field direction within the semiconductor material and how does doping the semiconductor affect its conductivity... | 31,360 | cqadupstack-physics |
101353 | Suppose a light wave with wavelength 3m. What happens if one tries to contain that wave within a 1m container? | Suppose a light wave with wavelength 3m. What happens if one tries to contain that wave within a 1m container? If I'm going about this entirely the wrong way or have wrong conceptions about light (which might be the case because I'm not a professional physicist), please tell me that instead. | What are the possible consequences when attempting to confine a light wave with a wavelength of 3 meters within a container that is only 1 meter long? Specifically, discuss any implications for wave behavior, such as standing wave formation or diffraction. | 8,803 | cqadupstack-physics |
113779 | Understanding the concept of cross section | The cross section is a tiny area, measured in barns ($10^{-28} \mathrm{m^2}$), which relates to the probability of a reaction. But I have trouble interpreting that number. For example how can I calculate, when two deuterons collide what's the chance that they fuse? I read in forums that they much more likely scatter. | What is the probability of fusion when two deuterons collide, given that the fusion cross section is approximately \( 2.5 \times 10^{-28} \mathrm{m^2} \) and the average relative velocity of deuterons in a thermal environment is about \( 10^5 \mathrm{m/s} \)? | 28,070 | cqadupstack-physics |
60649 | Find the bending moment of a pole attached to a moving block | I'm having trouble with the following problem.  _What I've done so far:_ x-y is the usual coordinate system. $a=\frac{F}{m}=\frac{800}{60}$ and the y component of this is $a_y=a\sin{60^\circ}$. To figure out the force acting on the rod and contributing to the momentum, I ta... | Given a rod with a mass of 20 kg that is accelerating upwards at an angle of 60 degrees with an applied upward force of 800 N, calculate the torque about the center of mass of the rod. Assume that the rod is not rotating and that the torque due to the weld forces is the only acting torque. What is the value of the torq... | 10,243 | cqadupstack-physics |
110705 | Does time travel violate conservation of mass/energy? | Imagine I exist at time $t_1$ and my mass is $m$. At time $t_2$ I time travel back to $t_1$. At time $t_1$ there is now a net increase of mass/energy in the universe by $m$. At time $t_3 = t_2 - x$ where $x < t_2 - t_1$, I travel back to t1 again. The net mass in the universe has now increased by $2 \times m$. Properly... | If I were to time travel back to a point in the past multiple times, each time bringing an additional mass \( m \) into the past, what would be the total increase in mass-energy in the universe after \( n \) travels, and how does this scenario relate to the conservation of mass-energy? | 29,274 | cqadupstack-physics |
103006 | How organic impurities in the air affects laser? | We have a Nd YAG laser pumped Optical Parameter Oscillator in our lab. A technician came to our lab (my professor called him for its maintenance) and while he was working on it, he told me that because of the organic impurities in the air, the crystals got contaminated. He showed me a layer formation on the crystal whe... | What types of organic impurities in the air can deposit on laser crystals, and what mechanisms lead to this contamination? Additionally, how can we quantify the impact of these impurities on the laser's performance? | 23,471 | cqadupstack-physics |
29002 | What sets the length scale of stratified rock formations? | Driving through areas of the American Southwest such as Utah and Arizona, you notice stratified rock formations everywhere. The grand canyon is the best known example. One striking thing is that the thickness (or height) of individual layers of rock seems to be roughly constant, within an order of magnitude. (Perhaps 2... | What is the average thickness of sedimentary rock layers in the Grand Canyon, and how does this thickness suggest long-term climatic or environmental conditions influencing their formation? | 32,165 | cqadupstack-physics |
73027 | Why is the radial direction the preferred one in spherical symmetry? | I am learning about electricity and magnetism by watching MIT video lectures. In the lecture about Gauss's law, while trying to calculate the flux through a sphere with charge in it, the lecturer states that the direction of the electrical field is radial, since it is the only preferred direction that there is (since t... | Why does spherical symmetry in a charge distribution imply that the electric field must be radial, and how does this relate to the concept of preferred directions in three-dimensional space? Additionally, can you provide a mathematical explanation or derivation to support this? | 15,728 | cqadupstack-physics |
9524 | A professional physics career without a degree? | I learned programming as a child, for fun. Now I am working as a programmer, even though I got a business major degree. I wonder if there are career paths for doing physics _other_ than becoming a researcher in a University or a professor, that are not _all_ about credentials? | What are three potential career paths in physics that do not primarily require a PhD or academic credentials, and what quantitative skills or knowledge would be particularly beneficial for each of these careers? | 6,622 | cqadupstack-physics |
112068 | Confused about the concept of time and time dilation | I am having a hard time understanding what is time. If scientists define time as a multiple of caesium frequency, then time itself is dependent on motion, so what if I have a number of particles that are at 0 Kelvin? Do these particle experience time by the fact it exist in the fabric of spacetime? And if so, is this t... | What is the relationship between temperature, particle motion, and the experience of time, specifically at absolute zero (0 Kelvin), and how does this relate to the concept of time dilation in the context of special relativity? | 31,198 | cqadupstack-physics |
112624 | On use of Hamiltonians for Helium | The Hamiltonian of helium can be expressed as the sum of two hydrogen Hamiltonians and that of the Coulomb interaction of two electrons. $$\hat H = \hat H_1 + \hat H_2 + \hat H_{1,2}.$$ The wave function for parahelium (spin = 0) is $\psi(1,2) = \psi_S(r_1, r_2)\dot \xi_A(s_1, s_2)$ with the first being a symmetric spa... | Given that the ground state wave function for parahelium can be expressed as $\psi(1,2) = \frac{1}{\sqrt{2}}[\psi_1(r_1)\psi_2(r_2) + \psi_2(r_1)\psi_1(r_2)]$, calculate the normalization constant for the spatial wave function $\psi_S(r_1, r_2)$ assuming that the individual wave functions $\psi_1(r)$ and $\psi_2(r)$ ar... | 13,524 | cqadupstack-physics |
133435 | Calculating Resultant Force and Torque | I'm working on a sandbox game that allows the player to build a spacecraft and attach thrusters in arbitrary locations on the hull of the spacecraft. The game is set completely in 2D. (I'm a programmer, not a physicist, so I apologize if my terminology is all wrong). I have need to actually calculate my own physics. Sa... | If only the right thruster, producing a force F, is activated while the left thruster is off, what is the resultant force vector acting on the center of mass of the spacecraft, and how does it influence the spacecraft's motion in terms of both linear acceleration and rotational dynamics? | 37,998 | cqadupstack-physics |
68937 | What is a photopeak? | I'm currently studying for an exam, where I'm looking into decays and gamma radiation. I then have a diagram where there are stuff like "Compton scattering", "Single Escape Peaks", "Double Escape Peaks" which all are calculated if I know the value of the photopeak. And all these three are actually quite well explained ... | What is the significance of the photopeak in gamma spectroscopy, and how is it quantitatively related to the energy of the incoming gamma photons? | 11,698 | cqadupstack-physics |
33113 | Dual Resonance Model: Fermions | I am going through Ramond's 1971 paper Dual Theory for Free Fermions Phys Rev D **3** 10, 2415 where he first attempts to introduce fermions into the conventional dual resonance model. I get the 'gist' of what he's doing: he draws an analogy of the bosonic oscillators satisfying the Klein-Gordon equation, and extends i... | In Ramond's 1971 paper on dual theory for free fermions, he introduces a correspondence principle expressed as \( p^2 - m^2 = \langle P \rangle \cdot \langle P \rangle - m^2 \) which transforms to \( \langle P \cdot P \rangle - m^2 \). What are the physical implications of this correspondence principle in the context o... | 17,153 | cqadupstack-physics |
33954 | How is the 'cluster decomposition principle' implemented in holographic theories? | Since holographic theories are non-local by definition, how is this principle implemented? Naively, it seems to me it is not, at least, in some sense. I would appreciate an explanation as simple as possible. | How is the non-locality principle in holographic theories quantitatively demonstrated in the context of black hole entropy, given the relationship between the surface area of the event horizon and the entropy? | 13,815 | cqadupstack-physics |
82160 | what happens during collision at molecular level? | When two massive bodies collide we treat them simply by their mass interactions with momentum and energy conservations. Down at the molecular level it must be more like a field particle collision for the particles coming in close contact, why dont we consider all these effects ? Are they included in our equations alrea... | When analyzing a collision between two massive bodies using momentum and energy conservation, how do the fundamental forces at the molecular level, such as electromagnetic interactions, affect the outcome of the collision, and how can these effects be quantitatively included in our classical equations? | 15,995 | cqadupstack-physics |
64568 | Base quantities and charges | Is there an unit of color charge? I haven't found it, so I suppose that it doesn't exist, if this is right, why? Isn't it supposed that every measurable quantity can be expressed in terms of base quantities? What about flavour charge? | What is the relationship between color charge and flavor charge in quantum chromodynamics, and how can we express these concepts in terms of measurable quantities? | 10,421 | cqadupstack-physics |
54728 | What is the Willmore energy of the Earth (or the geoid)? | Wikipedia defines the Willmore energy as: $$e[{\mathcal{M}}]=\frac{1}{2} \int_{\mathcal{M}} H^2\, \mathrm{d}A,$$ where $H$ stands for the mean curvature of the manifold $\mathcal{M}$. What is the Willmore energy of the Earth, or the geoid? | What is the Willmore energy of the Earth, approximated as a geoid, using the formula $$e[{\mathcal{M}}]=\frac{1}{2} \int_{\mathcal{M}} H^2\, \mathrm{d}A$$ and considering the mean curvature of the Earth’s surface? | 35,138 | cqadupstack-physics |
128231 | Remotely changing superconductor levitation height? | I want to be able to modify the height of a quantum locked superconductor. My original plan was to levitate the superconductor over an electromagnet and modify the current to said magnet (increase the current for higher levitation height, decrease for lower). Further research has made it apparent to me that this won't ... | What is the relationship between the height of levitation of a superconductor and the magnetic field strength produced by an electromagnet, and how can this relationship be used to predict the maximum height of levitation for a given type of superconductor? | 14,178 | cqadupstack-physics |
106043 | Can we always apply a pure torque at arbitrary positions on an object in practice? | I want to apply a **pure** torque to an object, say a square box on the ground. And I also require that the torque is generated on the corner of the square, not the center of mass. Is there any way for me to do that? I know there is torque motors. But imagine this, if I attach the torque motor the a corner of the squar... | How can I apply a pure torque of 5 Nm to a square box with a mass of 2 kg and a side length of 0.5 m at one of its corners, ensuring that it rotates around its center of mass? | 16,980 | cqadupstack-physics |
67041 | Why do ice cubes make a cracking sound when placed in fizzy wine (Prosecco)? | When placing ice cubes in a fizzy drink such as Prosecco, ice makes a cracking sound, after which the fizzy bubbles more than usual. What is the physics of this phenomenon?  | What is the increase in the rate of bubble formation in a fizzy drink, measured in bubbles per second, when ice cubes are added, and how does this relate to the temperature change and pressure effect in the drink? | 25,771 | cqadupstack-physics |
132317 | How did the gravity of the particles/objects behave at the edge of the expanding universe moments after big bang? | During a very short time after the big bang, the universe must have had an edge of space-time which is very close to all the matter in the universe. The particles which are close to or on the edge must also have gravity and other forces. How did those forces interact with the space-time boundary? And, if the range of g... | What was the approximate density of matter in the universe just after the big bang, and how does this relate to the gravitational forces acting at that time? | 23,870 | cqadupstack-physics |
47191 | At what velocity does sea water leave a pipe run into a fresh water lake (for equal surface levels)? | If I took a fresh water lake* whose surface is exactly as sea level, and connect it to the sea with a pipe filled with sea water, with both ends of the pipe at exactly the same depth from the surface, $h$, what is the correct way to calculate the velocity with which the salt water leaves the pipe from the depth $h$, an... | What is the velocity of salt water exiting a pipe at depth \( h \) when connected between a freshwater lake and the sea, considering the densities of fresh water (\( \rho_\text{fw} \)) and seawater (\( \rho_\text{sw} \))? Use Torricelli's law and the principle of hydraulic head to derive your answer. Assume the pressur... | 2,256 | cqadupstack-physics |
3314 | energy field of a newly created particle | The question is: How to calculate the energy of electrostatic field of a newly created particle. The usual formula involves integration _'all over space'_. According to GR I believe that _'all over space'_ means the interior volume with radius c*t_now, where t_now is the lifetime of the particle at the time of calculat... | Calculate the energy stored in the electrostatic field of a particle that has been created for a duration of 2 microseconds, assuming it has a charge of +1 coulomb and a constant electrostatic field strength of 10^6 N/C. Use the concept that the effective radius of the field at time t is given by \( r = ct \), where \(... | 17,215 | cqadupstack-physics |
33926 | Could the Higgs boson field be responsible for the dramatic mass increase when an object begins to travel close to the speed of light? | could the Higgs boson field be responsible for the dramatic mass increase incurred when an object nears the speed of light? | What is the relationship between the Higgs boson field and the relativistic mass increase experienced by an object as its velocity approaches the speed of light? | 21,774 | cqadupstack-physics |
29950 | How to apply Guass Law to Voltages | So, I know $\oint E\centerdot dA = 4\pi Q_{enc}$ I'm trying to solve for a TEM mode with two concentric (infinite) cylindrical wave guides of radius a and b, $a<b$. I know that for TEM modes, I can solve by assuming that the outside and inside are at two different potentials, $\pm V$. I'm told the solution is $\vec E=a... | How can I apply Gauss' Law to derive the electric field \(\vec E\) in a TEM mode configuration with two concentric infinite cylindrical waveguides of radius \(a\) and \(b\) (\(a < b\)), knowing that the potentials at the boundaries are \(\pm V\), and how would the resulting \(\vec E\) compare to the provided solution o... | 19,001 | cqadupstack-physics |
38124 | Why water is not superfluid? | My question is in the title. I do not really understand why water is not a superfluid. Maybe I make a mistake but the fact that water is not suprfluid comes from the fact that the elementary excitations have a parabolic dispersion curve but for me the question remain. An equivalent way to ask it is: why superfluid heli... | What are the key differences in the behavior of elementary excitations between superfluid helium and water, and how do these differences relate to the applicability of the Gross-Pitaevskii equation to superfluid helium but not to water? | 35,725 | cqadupstack-physics |
66153 | Problems related to Green's function? | My teacher told me to do a research studying some physics problems that has connection with Green's function on solving differential equations (with programmed numerical solutions) in my final year project, can you give me such problems to work on as an undergraduate? I found this but I need more interesting problems t... | What are some specific physics problems that can be solved using Green's functions in differential equations, and how can numerical programming techniques be applied to find their solutions? | 16,369 | cqadupstack-physics |
16151 | Alternative definitions of potential? | I hope this question is simple and can be quickly cleared up. In a 1D conservative dynamical system, I've always been taught that the potential function is the function $V(x)$ such that: $$F=-\frac{dV}{dx}$$ That makes sense to me, simply derived from the definitions of work and conservation of energy. However, just re... | In a 1D conservative dynamical system described by the equation \(\dot{x} = f(x)\), where \(f(x) = -\frac{dV}{dx}\), how does the relationship between the potential \(V(x)\) and the force \(f(x)\) change the interpretation of the dynamics compared to the standard Newton's second law \(F = m\ddot{x}\)? Can you provide a... | 1,302 | cqadupstack-physics |
94110 | Error propagation estimations for sine and cosine | My lab manual gives this: $B$ is a function of $A$, Greek are uncertainties... $$B + \beta = \sin(A + \alpha) = \sin(A)\cdot\cos(\alpha) + \sin(\alpha)\cdot\cos(A)$$ \--> because $\alpha$ is taken to be (at least relatively) small, $\cos(\alpha) \to 1$, and $\sin(\alpha) \to \alpha$, measured in radians. I see that $\c... | In the context of small angles, how can we mathematically justify that $\sin(\alpha) \approx \alpha$ while $\cos(\alpha) \approx 1$ as $\alpha$ approaches zero? What is the significance of these approximations in the behavior of the sine and cosine functions near the origin? | 4,631 | cqadupstack-physics |
105265 | Is there any scientific instrument right now to monitor complicated chemical reaction between atom? | What is some differnt way to use any scientific instrument right now to monitor complicated chemical reaction between atom?? | What scientific instruments can be used to quantitatively monitor the progress of a complex chemical reaction at the atomic level, and how do they work? | 22,110 | cqadupstack-physics |
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