Questions tagged [antimatter]

Analogous to matter, but with charge of the particles opposite to their ordinary matter counterparts.

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Interaction term in Lagrangian implying photon has no antiparticle?

I read that the QED Lagrangian interaction term ($-q\bar{\psi}\gamma^\mu\psi A_\mu$) implies that while electron-positrons come in pairs, a photon does not need to form in a pair (and hence it does ...
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Do laws of physics prohibit direct conversion of particles to antiparticles?

Can antiparticles only be created in pair production? How/which laws of physics prohibit direct conversion of say an electron to a positron? A neutron to an antineutron? I have seen a comment that it ...
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Switching particles for antiparticles in Feynman diagrams

While studying, I found a problem involving $e^-\nu_e$ and $e^-\bar{\nu}_e$ scattering, though this could also apply to $e^- e^-$ and $e^- e^+$ scattering if we wanted to keep everything within QED. ...
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Does the Schwinger effect prove matter and antimatter equal nothing?

Virtual particles or vacuum fluctuations are the pair annihilation/creation of matter and antimatter particles in and out of nothing. Theses particles are virtual, but we know they exist because of ...
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Is the following theory about the cause of expansion be true? [closed]

Statement: "The universe is expanding due to the constant emergence of a new space at every point in the universe." My thoughts: It is said that Dark Matter/ Anti Matter are opposites of ...
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What kind of matter is positronium?

What kind of matter is positronium? Normal matter, antimatter, exotic matter or something else? We know: Matter is made up of electrons, protons and neutrons. Antimatter is made up of positrons, ...
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Does Normal matter also include anti-matter and engery?

We have studied approx 4.6% of normal/ordinary matter in the universe and everything till now we observed are a part of this 4.6% I always have doubt. this 4.6% include all the matters and energies ...
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Would light bend the other way, if I use antimatter instead?

Imagine the following setup: an antimatter straw, an antimatter glass filled with antimatter water and we have antimatter atmosphere just in case. My question is: does Snell's law still apply here as ...
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A gram of antimatter reacting with a gram of matter releases Hiroshima-like energy, but is that true in practice?

My understanding is that a particle must meet its antiparticle. So if you a one-gram cube of, say, anti-gold and shot it into a one-gram cube of normal gold, how would you get the particles to come in ...
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Black hole radiation

Black hole radiation in which particle and antiparticle pairs are separated which ultimately leads to the 'evaporation', but why does the negative particle always enters the black hole? Why do the ...
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If antiparticles are particles moving back in time, would messages from the future be possible?

So, here's the idea: if Feynman's interpretation of antiparticles is true and antiparticles are particles moving back in time, then they are carrying with them information from the future, no? If that'...
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How is Hawking radiation supposed to work if the anti-particle escapes the black hole? [duplicate]

(Update: I answered my own question. See comment below.) OK, tell me what I'm missing. According to my research, Hawking radiation is as follows: a particle-anti-particle pair are created from ...
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Most correct intuition for vacuum energies in interacting and non-interacting field theories

It seems like a lot of pop science gets thrown around when explaining vacuum energy. For instance, our QFT lecturer descried the non-interacting field theory vacuum energy as 'purely Heisenberg ...
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Why do we conventionally label anti-particle solutions to Dirac equation with $-p$?

The spinor solutions to the dirac equation tend to be conventionally labelled as $u^s(\vec p)$ for particles and $v^s(- \vec p)$ for anti-particles. Am I correct in thinking that these anti-particles ...
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Euler-Lagrange equation for positron from QED lagrangian

Taking $e<0$ to be the charge of the electron, the Euler-Lagrange equation derived from taking the first variation of the $\psi$ field in the QED lagrangian $${\cal L} = - \frac 1 4 F_{\mu\nu}F^{\...
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Actual physicists: shoot down my hypothesis regarding antimatter, primordial black holes, and the origin of the universe [closed]

Let's get this out of the way up front: I'm no physicist and have no business proposing any of the things I'm about to propose. The likely outcome here is that someone with relevant education can ...
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Spin sign for antiparticle

I have this problem with the sign of the spinor for the antiparticle. In the chiral basis, a spinor is represented by $\psi =(\psi_{L},\psi_{R}$). Now, we consider a particle with mass = 0, so Dirac's ...
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Uses of antimatter in the present [duplicate]

Since the previous question by Jaime Soto is now nearly 12 years old, I wondered if there were any new practical Uses for Antimatter except PET and the treating of certain types of cancer. So, are ...
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Does the collision of a neutron and anti-neutron produce energy?

Following up on this post: Anti-Particle of Neutron, one very important part of it is unanswered. If a neutron collides with an anti-neutron, will it violently explode in a flash of energy? The ...
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Could Matter Go Backwards in Time?

In the real world, it seems that traveling backwards in time is impossible, but do we have a theorem in physics that would imply this fact? Some people (including Feynman) describe antiparticles as ...
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Why are only positive frequency mode functions allowed in Quantum field theory? How is this consistent with anti particles having negative energy?

In quantum field theory, one can redefine the particle creation and annihilation operators using Bogoliobov transformations, which can give rise to a different vacuum state, using a new set of ...
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What are the conditions needed for baryogenesis? [duplicate]

Physicists have created antimatter in the laboratory. But when they do, they create an equal amount of matter. That suggests that the Big Bang must have created matter and antimatter in equal ...
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Existence of Ground State of Dirac equation

In chapter four of Ryder, the author showed that there exists a ground state $|0\rangle$ for the Kelin-Gordon equation, just like the case of the linear harmonic oscillator. However, I was not able to ...
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Can a conventional QFT explanation of the "antitritium deficit" be offered such that it jibes with the Standard Model and QFT principles?

*the "antitritium deficit" used in the question refers to the attached image/data from Brookhaven National Laboratory STAR facility analyzed circa 2011, the parent article abstract is here: ...
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What is the time-dilation at the surface of an antineutron star? (Does antimatter generate gravitons, an extension of the SM, as matter does?)

The time-dilation at the surface of a [matter] neutron star is calculated to approximately be four times slower than flat space-time, conventional quantum mechanics treats antiparticles as traveling ...
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Penning trap with positrons: observing annihilations?

Has a single positron been deliberately put into contact with an electron to observe the results? If so, does the annihilation occur only when the two particles "touch" or is the definition ...
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Can an electron–positron plasma with $\mu_r=\varepsilon_r=2$ exist?

Can an electron–positron plasma with relative permeability and relative permittivity of 2 ($\mu_r=\varepsilon_r=2$) exist? How dense would it be and how would its constituents move? Can it keep those ...
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Why do the electron and position creation operators anti-commute?

I am learning QFT and is baffled by a minor problem. The electron and the positron should be distinguishable, as they have different charges. So why do their creation operators anti-commute? They ...
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How do you make antiprotons?

What is the reaction that makes antiprotons? I'm not a physicist so I might not understand the shorthand.
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Why an electron and a positron should have the same lifespan?

According to Particle Data Group: source: data Particles and their antiparticles (i.e. antimatter) have the same lifespan. The electron/positron for example have a minimum of 6.6E28 yr. This was ...
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Pauli exclusion principle and antimatter

Have the Pauli exclusion principle been proven to apply to antimatter experimentally?
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Understanding the derivation of equation 1.2 in Tom Banks's book of "Modern Quantum Field Theory". A source is also a sink

The book "Modern Quantum Field Theory" by Tom Banks recites in equation 1.1 a probability amplitude for a particle to be produced at $x$, then propagate freely from $x$ to $y$, where it is ...
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Antimatter Majorana and DIrac

i have a question , how did Dirac derive the existence of antimmater from his equation ?? $$i \hbar \gamma^\mu \partial_\mu \psi - m c \psi = 0$$ and why for the Majorana equation predicts the ...
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Isn't it possible for a matter to have mass of an electron but opposite charge? [duplicate]

I read that "Positrons" have the same mass as of an electron but it is oppositely charged but we don't call it a normal matter we have given a special name to it "anti matter". But ...
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Questions about Antimatter [closed]

Antimatter. It's a thing that exists and it's something that I wanna learn more about. Just gonna jump straight into the questions this time around instead of drawing things out with a long-winded ...
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Parton Distribution Functions - Antiquarks?

In all the PDF plots that I have seen so far (e.g. https://arxiv.org/abs/1111.5452 Fig. $3$ and $4$) the PDFs for sea or charm quarks contained only the strange or charm quark, but not the $\bar{s}$ ...
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What is the exchange particle in this Feynman diagram?

We just covered Feynman diagrams for the first time today, so please bear with me as a student who is not yet educated well in this subject. One question we did asked: "Draw the Feynman diagram ...
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Is an Anti-positron actually only a relativistic effect on the observed helicity of an electron?

I have read quite recently this article here: https://www.quantumdiaries.org/2011/06/19/helicity-chirality-mass-and-the-higgs/ in which it is explained that an Anti-positron is actually a different ...
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If electrons were just positrons moving backwards in time, then shouldn't we see them coming out of black holes?

I have read this question (What would happen if I crossed the shell of a hollow black hole?): In effect, the formerly spacelike direction inwards becomes timelike, and the singularity is in the ...
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Isospin for Antiparticles

In Quarks & Leptons: An Introductory Course in Modern Particle Physics by Halzen and Martin page 42 reads: The construction of antiparticle isospin multiplets requires care. It is well ...
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Can there be Neutrino and antineutrino oscillations?

I don't know have rigor knowledge in neutrino oscillations. I just know that there is not a definite mass state for a definite flavor Just like with spin where you might have eigenstate $|+\rangle_z$ ...
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Is a lack anti-matter related to the arrow of time?

Mathematically speaking, we know that antiparticles can be equivalently thought of as particles travelling backwards in time. We also know there is a distinct lack of anti-particles in the universe ...
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Complex conjugation of negative energy solutions of the Klein-Gordon-equation

In the university (of Cambridge) script "Gauge Field Theory" of Ben Gripaios on p.11 the positive and negative energy (or if you prefer positive & negative frequency) solutions of the ...
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Can quarks and antiquarks exist in an atom without annihilating?

Elaborating on antimatter, where atoms consist of antiprotons, antineutrons, and positrons Is it possible to have something in between? with antiprotons, positrons, and regular neutrons? Can such an ...
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How can they say that there is an antimatter/matter asymmetry when wherever you are there can only be one of the two?

I don't think we have any way of knowing that distant galaxies are not antimatter so that there really is an equal amount of both matter and antimatter. But if you randomly, not evenly, distributed ...
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Photons in orbit of moving ion

Recently, I've heard about successful experiment regarding Breit-Wheeler process. (Sample article:) https://www.sciencealert.com/physicists-claim-they-ve-finally-observed-matter-being-made-out-of-...
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Can neutronium, (as in the exotic -onium atom composed of $n\bar n$ and not the degenerate matter kind) exist?

First off I'd like to say yeas I know what neutron-degenerate matter aka neutronium is and how it's likely what's inside neutron starts, this isn't what the wuestion is abount. I am referring to an -...
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Did a particle really seem to go backwards in time during a collision experiment at LHC?

I distinctly remember the news of a weird particle which seems to have gone backwards in time .Probably a Higgs singlet It was probably a high energy collision between proton and proton . A particle ...
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Can antimatter exists in the form of compound?

I just found an article describing the cooling of the antimatter, "Laser cooling of antihydrogen atoms". Naturally, if there's something, one turned to be like to hold it. Once the ...
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Particle-antiparticle duality and special relativity

I was reading through Zee's QFT in a Nutshell and I reached the end of the second chapter, where Zee discusses the similarities between Compton scattering and electron-positron annihilation. While I ...

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