Questions tagged [mass]

The property of an object that determines how much it responds to a force in Newtonian mechanics, and how much it interacts with gravity in the Newtonian framework. Mass also refers to the intrinsic energy of a particle in particle physics. This tag does also cover effective mass.

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Conservation of Komar Mass

The definition of Komar Mass in GR is associated with one asymptotically flat end. However, a hypersurface may contain more than one end, such as the spacelike Einstein-Rosen bridge in Kruskal ...
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A Universal Upper Limit on Mass Within a Radius $R$?

Since the universe has a positive cosmological constant, there is an upper limit on the mass of the black holes as evident from the so-called Schwarzschild-de Sitter metric: $ds^2 = -f(r)dt^2 + \...
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Further explanation of the Penrose Conjecture

I'm currently a third year maths undergrad, writing a dissertation on the application of minimal surfaces in space. I have recently come across the Penrose Conjecture that the mass of a spacetime is: ...
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Classic mass predictions from Left-Right models with discrete symmetries?

I am covering the classic literature on predictions of Cabibbo angle or other relationships in the mass matrix. As you may remember, this research was a rage in the late seventies, after noticing that ...
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Estimating the displacement/force of a string (eg. guitar, piano) being struck by a mass (eg. by hammer or plectrum) at a given initial velocity

I have created a string audio synthesizer (eg. guitar, piano) based on physical modeling. It incorporates modeling for all the major phenomena that characterize a string. This includes things like ...
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Why is it that the equation of a massless scalar field *must* be conformal invariant?

I'm reading a paper [1], p.111 where it is said that: However, the equation of scalar field with zero mass must be conformal invariant while equation $\square\varphi=0$ does not satisfy this ...
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1answer
356 views

Why bound states in QFT have higher mass than single particle states?

In standard textbooks in QFT while discussing e.g. the Kallen-Lehmann formula (see e.g. Section 7.1 in the Peskin-Schroeder book) it is always assumed that bound states of two or more particles have ...
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How could particles with electric charge be massless before the electroweak symmetry breaking?

How could particles with electric charge be massless before the electroweak symmetry breaking? Wouldn't the energy stored in the electric field contribute to the mass of the particle?
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Energy conservation in cosmological phase transitions

Let us consider a cosmic phase transition, in which fermions $\psi_f$ condense and the vacuum expectation value $|\langle \bar{\psi}_f \psi_f\rangle |$ of the resulting fermion-bilinear field gives ...
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1answer
163 views

Correction to fermion mass in Supergravity mediated supersymmetry-breaking

I recently came across this paper about axino (fermion superparter of axion) mass in supergravity: https://doi.org/10.1016/0370-2693(92)90547-H In this paper, they think of a specific superpotential (...
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270 views

Is a universe without massive particles scale-invariant?

In a popular talk by Roger Penrose about spacetime geometry, when introducing his conformal cyclic cosmology starting at 17:15 I think he says that as soon as there are no massive particles left in ...
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A problem with ADM mass in the derivation of 1st law of black hole thermodynamics

The definition of ADM mass is $$M=\frac{1}{16\pi}\lim_{r\rightarrow\infty}\int \left(\frac{\partial h_{\mu\nu}}{\partial x^\mu}-\frac{\partial h_{\mu\mu}}{\partial x^\nu} \right)N^\nu dA$$ according ...
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329 views

Proof for the Mass gap of sine-Gordon action with $g \cos(\beta \Phi)$

This is the sine-Gordon action: $$ \frac{1}{4\pi} \int_{ \mathcal{M}^2} dt \; dx \; k\, \partial_t \Phi \partial_x \Phi - v \,\partial_x \Phi \partial_x \Phi + g \cos(\beta_{}^{} \cdot\Phi_{}) $$ ...
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967 views

Is Electromagnetic Mass Possible?

If the sinusoidal electric component of a light wave were off-set to one side of the magnetic component and then the smaller "lobe" were to cancel out with much of the larger side, then where would ...
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The change in mass of a black hole do to Hawking Radiation

Hawking radiation which is the result of virtual particles, which are always created in pairs,(particle/antiparticle) near enough to the event horizon of a black hole, that one of the pair falls in ...
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Instantons, renormalization, and the Schwinger Model

Instantons in QCD contribute to the up, down, and strange quark masses (see, e.g., Georgi and McArthur (1981) or Kaplan and Manohar (1986)). Some papers claim that this contribution is equivalent to ...
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108 views

How can one define a covariant rate of change of rest mass for an extended body?

For a point mass I can define a covariant rate of change of its rest mass as $\frac{d}{d\tau}m_0$ where $\tau$ is the proper time. How can I also define a covariant rate of change of rest mass for an ...
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What is the 't Hooft determinant?

The 't Hooft vertex/determinant is somehow generated by instantons and is responsible for the generation of mass gap in pseudo-Goldstone bosons, such as an axion. For example, the complex Peccei-...
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215 views

If negative mass should exist, how would conservation of momentum work?

Imagine that a particle with negative mass has been discovered. It is known to obey both the equivalence principle and Newton's second law. This means that the particle is a subject to repulsive ...
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95 views

Difference between inertial and gravitational mass in general relativity due to self-contribution of gravitational potential

In the work The relativistic problem of several bodies, Am. J. Math. 59(1), 9 (1937), Levi-Civita addresses the problem of the motion of $n$ bodies in general relativity. He solves simultaneously ...
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Can I compute mass of an object in a box based on the sound the object makes when shaken? (Barton Fink movie)

In this movie called "Barton Fink" the main character, Fink, is given a mysterious box with an object inside it, he shakes the box up and down, is it possible to calculate the mass of the object ...
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Inverse square law and the photon mass

I have seen many questions about this, but haven't really found the answer I was looking for. I was caught by an exercise that said: Consider two charges: $q$ (a test charge) and $Q$, at $\vec{R}...
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Is there an analog of the Komar mass for conformal Killing Fields?

Is there an analog of the Komar mass for conformal timelike Killing vector Fields? For a stationary spacetime M, the Komar mass may be given as: $$M=\oint_{\partial M}\sqrt{g_{00}}(2T_{\mu\nu}-g_{\...
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What are the Higgs masses for $SU(2) \times U(1)$ goes to $U(1)$ symmetry breaking with a complex triplet?

Consider an $SU(2)\times U(1)_Y\rightarrow U(1)_{EM}$ theory that is broken via a complex triplet with hypercharge 2. The potential is of the form \begin{align} V(\Phi) = -m^2\Phi^\dagger\Phi + \...
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106 views

Why is the top quark mass reconstructed too high when the bottom quarks were swapped (semileptonic decay of a ttbar pair)?

I use a dataset containing simulated events of semileptonic $t\bar{t}$ decays ($t\bar{t} \rightarrow W⁺b W⁻ \bar{b} \rightarrow q\bar{q}bl\nu_l\bar{b}$) at CMS, LHC. For each event, the four-momenta ...
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626 views

What is the effective electron mass in a plasma?

Is there a way to calculate the effective electron mass in plasmas? Effective electron mass is usually defined as varying from the vacuum electron mass in solid state physics. However, momentum ...
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117 views

Asymtotically flat spacetime applicable for spacetimes which are not diffeomorphic to $\mathbb{R}^4$

I wanted to investigate changes on a compact 4-manifold $M$. More specifically it is the K3-surface. I follow a paper by Asselmeyer-Maluga from 2012. The idea there was to make sure that the manifold ...
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291 views

What Would Negative Mass Do To Spacetime?

It's known that positive mass bends space-time to create a curvature. But if something had negative mass what would it do? Make it flat or like a crest?
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714 views

The question about Lorentz invariance of the helicity quantum number for the massless particles

I need to show that helicity is Lorentz invariant (under the proper Lorentz transformation) for the massless particles. I heard about most frequently used argument which contains an idea of ...
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378 views

Reducing massive representation of the Poincare group to the massless one

I want to ask about the connection for massive and massless representation of the Poincare group. Sorry for the awkwardness. First I must to represent the formalism for both of cases. Massive ...
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597 views

Truck Mass & “4th power law”

Is it true that the damage caused to a road surface is proportional to the 4th power of vehicle axle weight, and if it is, what factors cause it to be related by a power of 4, or is it just the ...
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Mass in Wilsonian RG (vs. mass in ordinary RG)

The essence of Wilson RG can be described in tree steps: Initially we have some theory on scale $\Lambda$. Lower cut-off $\Lambda^\prime =\zeta^{-1}\Lambda<\Lambda$ and integrate out d.o.f. with $\...
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1answer
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In general, conservation laws do not hold whenever the center of mass of the system is moving?

I am currently studying Classical Mechanics, fifth edition, by Kibble and Berkshire. Problem 3 of chapter 1 is as follows: Consider a system of three particles, each of mass $m$, whose motion is ...
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Phase transition in 2+1D QED for $\theta =\pi$

QED in 1+1 dimensions with a massive fermion, called the massive Schwinger model, has a phase transition at $\theta=\pi$ for some finite critical mass $m_c$. Equivalently, one can say that the ...
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How to estimate the mass of an incoming asteroid?

A second galactic visitor has just been observed: see this link. For a mass which is small enough to have no noticable effect on other masses, is there any other way to infer the mass? Its own motion ...
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How Supersymmetry solves the hierarchy problem

The fermion contribution to the Higgs mass is $$\Delta m^2_{H}=-\frac{|\lambda_{f}|^2}{8\pi^2}\Lambda^2_{UV}+\dots$$ And the scalar contribution is: $$\Delta m^2_{H}=\frac{\lambda_{s}}{16\pi^2}\...
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Are conservation of mass and conservation of energy *independent* constraints for physical systems?

I'm modeling fluid systems and want to use conservation of mass (aka 'continuity') and conservation of energy as constraints to help solve for certain system parameters. But it occurred to me that the ...
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1answer
63 views

Interpretation of a CLs exclusion plot

I have some trouble with the interpretation of this plot. The plot on the right shows the CLs values for the SM Higgs boson hypothesis as a function of the Higgs boson mass in the range 110–145 GeV. I ...
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How do we determine who eats who (or which field gets massive) in a Higgs phase transition?

Consider the following theory in which a $2$-form field $B_{\mu\nu}$ with field strength $P_{\alpha\mu\nu}=\partial_{[\alpha}B_{\mu\nu]}$ is coupled to a $3$-form gauge field $C_{\alpha\beta\gamma}$ ...
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Questioning whether gravity is strictly attractive. Is there a possibility for repulsion?

My teacher wanted to test our understanding before starting a new topic. The question he gave goes something like this “There are 2 vacuums present here about which there is an abundance of mass ...
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What would a universe with a long range weak force look like?

If the W's and Z bosons were massless at low energies (i.e. no Higgs interaction), what would the universe look like? Would there be "weak bound states" ? How would electromagnetic theory differ with ...
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Can mass still be observed in our universe after moving from a black-hole to a white-hole?

This question is based on the recent papers on LQG black-holes by Abhay Ashtekar. Quantum extension of the Kruskal spacetime and Quantum Transfiguration by Kruskal Black Holes When mass moves from ...
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1answer
77 views

What does it mean for a graviton to have mass?

On wikipedia we can read: Astronomical observations of the kinematics of galaxies, especially the galaxy rotation problem and modified Newtonian dynamics, might point toward gravitons having non-...
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1answer
61 views

Inertial and gravitational Mass

Why definition of mass is not stated as " the property of object to change radius of curvature of space time fabric is called mass"
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Geometric Explanation for the Equality of Active and Passive Gravitational Masses

In Newtonian gravity, as such, there are three masses: the active gravitational mass (the mass that generates the gravitational field), the passive gravitational mass (the mass that responds to the ...
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Can topological degrees of freedoms interact?

Question Can topological degrees of freedom interact with: other topological dof's other local dof's Premise For concreteness, I can't understand why the following term will not be allowed in a ...
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Does the black-body radiation formula (Stefan-Boltzmann) change if the photon turns out to be massive?

The black-body radiation formula, the Stefan–Boltzmann law, is derived treating photons as massless. Questions: What would the Stefan–Boltzmann law look like if derived assuming that photons have ...
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309 views

Why a neutrinoless double beta decay implies a massive neutrino?

I know neutrinos have mass thanks to the observation of the neutrino oscillations between one type to another (that cannot happen if they are massless particles because the mixing matrix will not ...
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61 views

Neutrinos at the OPERA experiment

The probability that a neutrino oscillates from a species $a$ to a species $b$ is given by \begin{equation} P(a \to b) = \sin^2 (2 \theta_{ab}) \sin^2 \left( 1.27 \frac{\Delta m^2 L}{E_\nu} \right) \...
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Defining inertial mass scale

I am following the approach to define mass scale as given in the book 'Newtonian Mechanics' by A.P.French (page 171). Take different objects labeled 1, 2 and 3, pull them one at a time with the same ...

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