What is needed to creat Proton?

[Dandav]

Let's assume that somewhere in the open space there is a mighty accelerator and we have full control on it.

We can set its size, its Power (including EM energy), Its gravity, Its Temp, its Pressure and so on.

I assume that in this accelerator we can generate particles/antiparticles as electron/positron and quarks/antiquarks (Up & Down).

However, proton is a complex particle as it is a combination of two up quarks, one down quark + gluons while there is no anti-proton or anti-gluons in the nature.

Therefore, do you agree that there is no way to directly create a proton/antiproton in this accelerator?

Hence, could it be that the only way to create a proton is by first creating the Up/down quarks/antiquarks, and just after having the correct quarks we can add the gluons in order to have real proton?

Never the less, as there is no anti-gluons in the nature, how can we get a gluons to be added to those Up/Down quarks in order to set a proton?

[Vmedvil5]

16 hours ago, Dandav said:

Let's assume that somewhere in the open space there is a mighty accelerator and we have full control on it.

We can set its size, its Power (including EM energy), Its gravity, Its Temp, its Pressure and so on.

I assume that in this accelerator we can generate particles/antiparticles as electron/positron and quarks/antiquarks (Up & Down).

However, proton is a complex particle as it is a combination of two up quarks, one down quark + gluons while there is no anti-proton or anti-gluons in the nature.

Therefore, do you agree that there is no way to directly create a proton/antiproton in this accelerator?

Hence, could it be that the only way to create a proton is by first creating the Up/down quarks/antiquarks, and just after having the correct quarks we can add the gluons in order to have real proton?

Never the less, as there is no anti-gluons in the nature, how can we get a gluons to be added to those Up/Down quarks in order to set a proton?

To create a proton and anti-proton pair from energy all you need to do is get a photon with around 2 Gev of energy and it will go through pair production and generate an anti-proton and proton pair. Link = Pair Production – EWT (energywavetheory.com)

"Before we get to the actual answer, there's something that needs to be clarified about the reaction as you've written it down. The reaction γ→e−+e+γ→e−+e+ is not a valid reaction, because it violates conservation of momentum. To see this, consider a photon with energy 2me2me. Since 2me2me is precisely the energy of an electron-positron pair at rest, the momentum of the system is zero after pair production. But since the energy of the initial photon was nonzero, the momentum of the photon was also nonzero. The momentum of the photon is not equal to the total momentum of the electron-positron pair, so this reaction cannot happen as stated (this argument also works when the photon's energy is greater than 2me2me, it's just more straightforward to see in this particular special case).

To see how pair production actually works, let's look at the reverse reaction: electron-positron annihilation, which is the reaction e−+e+→γ+γe−+e+→γ+γ. You can see that, unlike the process you described, two photons are produced by an annihilating electron-positron pair. This means that there's no momentum-conservation issue even when the electron and positron annihilate at rest; the two photons have equal energy and travel away from the vertex back-to-back, so the total momentum before and after annihilation is zero.

Since quantum electrodynamics is time-reversal invariant, the reaction for pair production should look like the reverse of the reaction for electron-positron annihilation. Therefore, the actual process for pair production is γ+γ→e−+e+γ+γ→e−+e+. But this isn't the way that pair production is usually described (people usually talk about a single photon producing a particle-antiparticle pair). Why is this?

The answer is that the second photon is usually a virtual photon, a mathematical tool used to describe one of the produced charges' interaction with some other nearby charge. Pair production cannot occur spontaneously in a complete vacuum. There has to be some other charged object somewhere in the universe that can carry off the difference in momentum between the initial photon and the electron-positron pair. An example diagram of this process is below:

Fortunately, even in intergalactic space, there's still at least some amount of charge floating around, so this typically isn't a concern, and as a result we tend to omit the other virtual photon when we discuss pair production colloquially.

---

With that said, there are two essentially unrelated questions being asked here:

Can you produce a proton-antiproton pair from a photon in a way analogous to electron-positron pair production?

The answer to this is yes, it's definitely possible. All you would need is a photon with energy greater than 2mp2mp, which is roughly 1.876 GeV, and there would be some chance of it happening. However, a photon with energy that high can also produce a particle-antiparticle pair of anything with electrically-charged constituents that is lighter than a proton, which includes electrons and many types of mesons (e.g. pions). So you wouldn't be guaranteed to see proton-antiproton pair production for a single given photon of this energy or higher, but if you had enough of them, then you would eventually see the process you described happen (the same caveats apply - you can't do this in an empty universe, one of the produced particles has to exchange a virtual photon with some external charge). This process tends to be really rare simply because there aren't really any natural processes that generate photons that have such high energies.

How are proton-antiproton pairs produced?

Probably the most common mechanism, both in cosmic-ray antimatter generation and in the laboratory, is inelastic scattering of a proton off of a nucleus, p+A→p+p¯+p+Ap+A→p+p¯+p+A. For cosmic-ray protons, AA is typically a nucleus in the interstellar medium. For laboratory protons, AA is typically a nucleus in some sort of collision target in an accelerator beamline."

and also, there is synthetic particle confinement synthesis to consider, link = https://www.scienceforums.com/topic/36969-synthetic-particle-confinement-synthesis/

 

Edited November 12, 2022 by Vmedvil5

[Vmedvil5]

4 hours ago, JeffreysTubes8 said:

Wow you're going the extra mile to try and sell useless information and obfuscate actual physics into oblivion.

A photon can't produce a proton. Particle accelerators like CERN don't work like that.  

You would be wrong, pair production is well known mainstream physics, link = Pair production - Wikipedia and Proton-Antiproton Pair Production in Two-Photon Collisions at Belle (researchgate.net)

Edited November 18, 2022 by Vmedvil5

[Dandav]

On 11/12/2022 at 11:22 PM, Vmedvil5 said:

Can you produce a proton-antiproton pair from a photon in a way analogous to electron-positron pair production?

The answer to this is yes, it's definitely possible. All you would need is a photon with energy greater than 2mp2mp, which is roughly 1.876 GeV, and there would be some chance of it happening. However, a photon with energy that high can also produce a particle-antiparticle pair of anything with electrically-charged constituents that is lighter than a proton, which includes electrons and many types of mesons (e.g. pions). So you wouldn't be guaranteed to see proton-antiproton pair production for a single given photon of this energy or higher, but if you had enough of them, then you would eventually see the process you described happen (the same caveats apply - you can't do this in an empty universe, one of the produced particles has to exchange a virtual photon with some external charge). This process tends to be really rare simply because there aren't really any natural processes that generate photons that have such high energies.

Thanks for the great explanation.

 

On 11/18/2022 at 10:41 AM, JeffreysTubes8 said:

A photon can't produce a proton. Particle accelerators like CERN don't work like that.  

Could it be that CERN is just too small?

Could it be that in the nature three are some mighty particle accelerators?

Let's focus on the SMBH' accretion disc:

This aria is under extreme gravitational force, Electromagnetics field, Pressure....

The plasma there is full with ultra-high temp (10^9 c) particles that orbit at almost the speed of light (0.3c).

So, could it be that this ultra-high temp & orbital velocity indicate that the particles at the accretion disc have been created by the EM + Gravitational force of the SMBH in the process that is called pair production?

On 11/18/2022 at 3:17 PM, Vmedvil5 said:

pair production is well known mainstream physics, link = Pair production - Wikipedia and Proton-Antiproton Pair Production in Two-Photon Collisions at Belle (researchgate.net)

Could it be that some of those new created particales have enough energy to generate proton-antiproton pair production while they colide with each other?

Edited November 25, 2022 by Dandav

[Vmedvil]

On 11/25/2022 at 12:00 AM, Dandav said:

Thanks for the great explanation.

 

Could it be that CERN is just too small?

 

CERN is fine and plenty large enough, there can be anti-proton and proton pair production at CERN from photons, Link = Proton-Antiproton Pair Production in Two-Photon Collisions at LEP - CERN Document Server

Edited March 24 by Vmedvil

[oldpaddoboy]

What is needed to create protons, are conditions that existed 3 minutes post big bang. Temperatures and pressures were such that quarks were able to  join and we had a first atomic nuclei. https://en.wikipedia.org/wiki/The_First_Three_Minutes  380,000 years later, temperatures had dropped sufficiently to enable electrons to couple with atomic nuclei, and our first light elements Hydrogen and Helium were formed.

[Dandav]

On 4/1/2024 at 3:37 AM, oldpaddoboy said:

What is needed to create protons, are conditions that existed 3 minutes post big bang. Temperatures and pressures were such that quarks were able to  join and we had a first atomic nuclei. 

In order to understand the first 3 minutes post big bang, we must understand what kind of energy is locked in a quark or proton.

In the following article it is stated:

https://www.researchgate.net/publication/325859308_Radiation_Pressure_and_E_mc
"To show that the equation E=mc² was already implicit in Maxwell’s 1861 paper “On Physical Lines of Force” and that it doesn’t mean that mass is equivalent to energy, but rather it relates to the propagation of electromagnetic radiation through an elastic solid."

"Maxwell is able to conclude that light is a transverse wave in an elastic solid that is also the cause of electric and magnetic phenomena."

"We also know from the 1932 Carl D. Anderson experiment that this energy is the 1.02 MeV associated with gamma radiation, and that it corresponds exactly to 2mc², where c is the speed of light [6]. Hence it follows that the circumferential speed of the electrons and positrons in the dipoles that make up of this elastic solid is equal to the speed of light."

"Maxwell saw a way of linking the result to the transverse elasticity in the displacement mechanism within a background elastic solid, where the equation E=mc² is  tied up in this relationship through fine-grained centrifugal pressure. All of this preceded the electromagnetic wave equation of 1864"

 

In the following article it is stated:

https://newton-relativity.com/alternative-approach-to-theory-of-relativity/derivation-of-emc²-from-classical-physics

 

"In the third and fourth chapters of the book “Newton and Relativity”, it is shown that the equivalence of mass and energy is a consequence of the conservation of momentum in the interaction between matter and electromagnetic radiation.

Derivation of E=mc² based on “radiation pressure”

Using a thought experiment (see animation), the equation E=mc² is easily obtained from the relationship of the electromagnetic momentum p=E/c.

According to this principle, the momentum of the emitted radiation E/c is equal to the momentum of the emitting body: 

(m−Δm)v=Ec  Where E represents the energy of electromagnetic radiation.

 So, do you agree that E=mc² doesn’t mean that mass is equivalent to energy, but rather it relates to the propagation of electromagnetic radiation through an elastic solid?

In other words, the energy E in any quark / proton represents the energy of electromagnetic radiation.

Please remember that the energy in CERN is based on electromagnetic energy.

Therefore, do you agree that electromagnetic energy is needed for the creation of any quark, proton and Higgs Boson.

Edited April 6 by Dandav

[Vmedvil]

39 minutes ago, Dandav said:

In order to understand the first 3 minutes post big bang, we must understand what kind of energy is locked in a quark or proton.

In the following article it is stated:

https://www.researchgate.net/publication/325859308_Radiation_Pressure_and_E_mc
"To show that the equation E=mc² was already implicit in Maxwell’s 1861 paper “On Physical Lines of Force” and that it doesn’t mean that mass is equivalent to energy, but rather it relates to the propagation of electromagnetic radiation through an elastic solid."

"Maxwell is able to conclude that light is a transverse wave in an elastic solid that is also the cause of electric and magnetic phenomena."

"We also know from the 1932 Carl D. Anderson experiment that this energy is the 1.02 MeV associated with gamma radiation, and that it corresponds exactly to 2mc², where c is the speed of light [6]. Hence it follows that the circumferential speed of the electrons and positrons in the dipoles that make up of this elastic solid is equal to the speed of light."

"Maxwell saw a way of linking the result to the transverse elasticity in the displacement mechanism within a background elastic solid, where the equation E=mc² is  tied up in this relationship through fine-grained centrifugal pressure. All of this preceded the electromagnetic wave equation of 1864"

 

In the following article it is stated:

https://newton-relativity.com/alternative-approach-to-theory-of-relativity/derivation-of-emc²-from-classical-physics

 

"In the third and fourth chapters of the book “Newton and Relativity”, it is shown that the equivalence of mass and energy is a consequence of the conservation of momentum in the interaction between matter and electromagnetic radiation.

Derivation of E=mc² based on “radiation pressure”

Using a thought experiment (see animation), the equation E=mc² is easily obtained from the relationship of the electromagnetic momentum p=E/c.

According to this principle, the momentum of the emitted radiation E/c is equal to the momentum of the emitting body: 

(m−Δm)v=Ec  Where E represents the energy of electromagnetic radiation.

 So, do you agree that E=mc² doesn’t mean that mass is equivalent to energy, but rather it relates to the propagation of electromagnetic radiation through an elastic solid?

In other words, the energy E in any quark / proton represents the energy of electromagnetic radiation.

Please remember that the energy in CERN is based on electromagnetic energy.

Therefore, do you agree that electromagnetic energy is needed for the creation of any quark, proton and Higgs Boson.

This is all correct, the Photons which are electromagnetic wave bosons give the energy to gluons which govern the strong nuclear force which are Strong nuclear force's bosons. The process is called the Higgs Mechanism or Tachyon Condensation which follows E = MC^2. The energy of the photon causes Color Confinement within the proton where the quarks are glued together by gluon bosons which are created by the photon's energy.

"Confinement (e.g Espiru 94) is the (expected) phenomenon in Yang-Mills theory generally and especially in quantum chromodynamics that the fundamental quarks, which the YM/QCD-Lagrangian density actually describes, must form baryonic bound states which are neutral under the color charge – the mesons and hadrons"

Link = Color and Confinement (pitt.edu)

"The Higgs mechanism breaks electroweak symmetry in the Standard Model, giving mass to particles through its couplings."

Link = higgs_mechanism.pdf (uni-muenchen.de)

"Tachyon condensation is a process in which a tachyonic field—usually a scalar field—with a complex mass acquires a vacuum expectation value and reaches the minimum of the potential energy."

Link = [hep-th/9912249] Tachyon condensation in string field theory (arxiv.org)

 

Edited April 6 by Vmedvil

[Dandav]

10 hours ago, Vmedvil said:

This is all correct, the Photons which are electromagnetic wave bosons give the energy to gluons which govern the strong nuclear force which are Strong nuclear force's bosons.

Thanks

In the following article it is stated:

PAIR CREATION IN THE PULSAR MAGNETOSPHERE

https://iopscience.iop.org/article/10.1086/344133/pdf

We present numerical simulations of the electron-positron plasma creation process in a simple neutron star magnetosphere.

An electron-positron pair plasma is a key ingredient in most models of pulsar radio emission. This plasma is assumed to come from a pair cascade that occurs in the open field line region close to the star’s magnetic axis

In the strong magnetic fields of pulsars, these primary photons are susceptible to magnetic one-photon electron-positron pair creation (Tsai & Erber 1974).

Hence, do you agree that electromagnetic wave that is created by strong magnetic fields (of pulsar/neutron star) could be converted into photon & electron-positron pair?

[Moontanman]

On 11/12/2022 at 12:37 AM, Dandav said:

However, proton is a complex particle as it is a combination of two up quarks, one down quark + gluons while there is no anti-proton or anti-gluons in the nature.

Never the less, as there is no anti-gluons in the nature, how can we get a gluons to be added to those Up/Down quarks in order to set a proton?

A gluon is its own anti particle in the same way a photon is its own anti particle.

https://www.chemeurope.com/en/encyclopedia/Gluon.html

Quote

Properties

The gluon is a vector boson; like the photon, it has a spin of 1. While massive spin-1 particles have three polarization states, massless gauge bosons like the gluon have only two polarization states because gauge invariance requires the polarization to be transverse. In quantum field theory, unbroken gauge invariance requires that gauge bosons have zero mass (experiment limits the gluon's mass to less than a few MeV). The gluon has negative intrinsic parity and zero isospin. It is its own antiparticle.

 

[oldpaddoboy]

 

22 hours ago, Dandav said:

”Therefore, do you agree that electromagnetic energy is needed for the creation of any quark, proton and Higgs Boson.

In my own words, no. Again what is needed are conditions that existed at around 3 minutes post big bang.  At that time it would have been the temperatures and pressures that existed then, when the universe/space/time was a lot hotter and denser, plus whatever energy created by the decoupling of the Superforce and the phase transitions and false vacuums plus the impetus from the big bang itself and Inflation.  

I'm sure far more professional explanations are available. Just a question in return... You are not by any chance pushing or promoting the long defunct electric/Plasma universe hypothetical are you?  

Of course the most damning aspect of electric/Plasma hypothesis, is that it has no maths, (the language of physics) to support it, and it ignores many aspects of accepted mainstream physics that are beyond doubt...Einstein's relativity for one, and time dilation, ( which if the appropriate maths was not fed into our gps satellites, our  gps systems would not work) ... also black holes. (which we have now imaged) But that's another subject and probably off topic. 

Edited April 7 by oldpaddoboy

[Dandav]

19 hours ago, oldpaddoboy said:

In my own words, no. Again what is needed are conditions that existed at around 3 minutes post big bang. 

I didn't ask about the Big Bang.

I only wish to understand if there is any possibility for any sort of particle (As Higgs Boson, Boson, quark, gluons, proton...) to be created by the strong magnetic fields of pulsars/magnetar?

Don't you agree that photons are electromagnetic wave bosons?

On 4/6/2024 at 8:45 AM, Vmedvil said:

This is all correct, the Photons which are electromagnetic wave bosons give the energy to gluons which govern the strong nuclear force which are Strong nuclear force's bosons.

Do you reject the following explanation? 

23 hours ago, Dandav said:

PAIR CREATION IN THE PULSAR MAGNETOSPHERE

https://iopscience.iop.org/article/10.1086/344133/pdf

We present numerical simulations of the electron-positron plasma creation process in a simple neutron star magnetosphere.

Please remember that the magnetic fields at those neutron stars could be millions or trillions of times stronger than the fields at CERN.

As higgs boson had been created at CERN, why at the neutron star' magnetosphere near its event horizon, under severe pressure due to its high gravity, high temp, there is no possibility for any sort of boson / photon to be created?

19 hours ago, oldpaddoboy said:

Electric/Plasma universe hypothetical

Sorry, what is it? I'm not aware about that theory.

Edited April 7 by Dandav

[oldpaddoboy]

3 hours ago, Dandav said:

I didn't ask about the Big Bang.

I only wish to understand if there is any possibility for any sort of particle (As Higgs Boson, Boson, quark, gluons, proton...) to be created by the strong magnetic fields of pulsars/magnetar?

The question asked was about conditions necessary to create protons. I stand by my answer that the conditions necessary would be those that existed at t+3 minutes. 

3 hours ago, Dandav said:

Sorry, what is it? I'm not aware about that theory.

It isn't a theory. It was a crazy hypothetical fabricated decades ago, to attempt to explain that which is already explained by the present standard cosmology model, without any maths. 

Edited April 7 by oldpaddoboy

[Vmedvil]

On 4/6/2024 at 12:30 PM, Dandav said:

 

Hence, do you agree that electromagnetic wave that is created by strong magnetic fields (of pulsar/neutron star) could be converted into photon & electron-positron pair?

I am uncertain if strong magnetic fields can create photons directly, I don't think they can.

13 hours ago, Dandav said:

 

As higgs boson had been created at CERN, why at the neutron star' magnetosphere near its event horizon, under severe pressure due to its high gravity, high temp, there is no possibility for any sort of boson / photon to be created?

 

At CERN, the particles are created by accelerating positively charged protons to near to speed of light where they collide with another positively charged proton, which causes all that kinetic energy that was given to the protons via the magnetic field to convert into massive particles such as the Higgs Boson. I don't think a magnetic field's energy can be directly converted into photons or Higgs Bosons. It is the proton collision that converts the energy into these particles at CERN. The Magnetic Field just accelerates the charged Protons to near the speed of light and it is not a direct conversion of energy at CERN from magnetic to massive particles.

"The Large Hadron Collider is the most powerful accelerator in the world. It boosts particles, such as protons, which form all the matter we know. Accelerated to a speed close to that of light, they collide with other protons. These collisions produce massive particles, such as the Higgs boson or the top quark."

"An accelerator can circulate a lot of different particles, provided that they have an electric charge so that they can be accelerated with an electromagnetic field. The CERN accelerator complex accelerates protons, but also nuclei of ionized atoms (ions), such as the nuclei of lead, argon or xenon atoms. Some LHC runs are thus dedicated to lead-ion collisions"

Link = Accelerators | CERN (home.cern)

Edited April 8 by Vmedvil

[OceanBreeze]

14 hours ago, Dandav said:

 

I only wish to understand if there is any possibility for any sort of particle (As Higgs Boson, Boson, quark, gluons, proton...) to be created by the strong magnetic fields of pulsars/magnetar?

Please remember that the magnetic fields at those neutron stars could be millions or trillions of times stronger than the fields at CERN.

As higgs boson had been created at CERN, why at the neutron star' magnetosphere near its event horizon, under severe pressure due to its high gravity, high temp, there is no possibility for any sort of boson / photon to be created?

 

I could not answer this question without doing a bit of research.

This is a NASA image of the Crab Nebula taken from optical and X-ray data from the Chandra Observatory:

Brief explanation written by a professional astronomer: The Crab Pulsar, a city-sized, magnetized neutron star spinning 30 times a second, lies at the center of this tantalizing wide-field image of the Crab Nebula. A spectacular picture of one of our Milky Way's supernova remnants, it combines optical survey data with X-ray data from the orbiting Chandra Observatory. The composite was created as part of a celebration of Chandra's 15 year long exploration of the high energy cosmos. Like a cosmic dynamo the pulsar powers the X-ray and optical emission from the nebula, accelerating charged particles to extreme energies to produce the jets and rings glowing in X-rays. The innermost ring structure is about a light-year across. With more mass than the Sun and the density of an atomic nucleus, the spinning pulsar is the collapsed core of the massive star that exploded, while the nebula is the expanding remnant of the star's outer layers. The supernova explosion was witnessed in the year 1054.

Some more information from a different site, explaining how 0-charge neutrons can act as a dynamo to create a powerful magnetic field; when we know that magnetic fields are created by moving electric charges.

QUOTE

“The key is that a neutron star isn’t just a simple ball of neutrons; it’s actually layered. As we progress from the outside-in, we find layers of:

    electrons, followed by

    the nuclei of atoms (like iron), followed by

    a layer where nuclei are layered (like impurities) inside an ocean of neutrons, followed by

    a transition zone to the core,

    where the core is a neutron superfluid (a liquid-like phase with absolutely zero friction) along with charged-particle impurities of various masses inside of it.

It’s not like having one single, neutral entity at all. And don’t forget that neutrons themselves are not fundamental, neutral particles, they themselves are made up of charged particles that have different charges and masses from one another.

And at approximately 10 km in radius — with all the angular momentum of a typical Sun-like star — these things rotate at speeds of between 10-and-70% the speed of light!

In short, that’s a recipe for a magnetic field on the order of 100 million Tesla, or about a trillion times what we find at the Earth’s surface.

The neutrons themselves have intrinsic magnetic moments (since they’re made up of these charged quarks), and the incredibly high energies inside the neutron star can not only create particle/antiparticle pairs, but can create exotic particles as well. The charged particles that exist inside the neutron star are highly conductive, plus there are still gravitational, density, temperature and conductivity gradients inside of the neutron star.”

UNQUOTE

 

[Which would seem to answer your question, IF we accept the correctness of this source.]

 

[Dandav]

3 hours ago, OceanBreeze said:

the incredibly high energies inside the neutron star can not only create particle/antiparticle pairs, but can create exotic particles as well.

Wow!

3 hours ago, OceanBreeze said:

[Which would seem to answer your question, IF we accept the correctness of this source.]

Thanks

I have found one more interesting article:

Pulsar surprises astronomers with record-breaking gamma-rays

https://www.space.com/vela-pulsar-highest-energy-radiation-gamma-rays

"Nearly 1,000 light-years from where you're sitting lies a spinning, highly magnetized neutron star that is so dense, a tablespoon of it equals something like the weight of Mount Everest.

this object seems to have spit out gamma-ray photons — which are associated with wavelengths that carry the most energy of all electromagnetic spectrum waves — holding at least 20 teraelectronvolts (TeVs), or 20 trillion electronvolts

Arache Djannati-Ataï, .. says you'd need about 2,000,000 typical solar flare photons to make one 20 TeV photon"

 

So do we agree that neutron star can create particle/antiparticle pairs including photons and exotic particles by its mighty MAGNETOSPHERE?

[Dandav]

Those Pulsars are relatively close to us (1,000 Ly & 6,000 Ly).

1,000 LY is the diameter of the Orion arm. In galactic measurements it is like a walking distance. Therefore, they should have good visibility.

I do understand that they observe the creation of particle/antiparticle pairs including photons.

However, I wonder what kind of particles creation they see that are called exotic particles.

Does it mean unknown Bosons/quarks...?

If so, could it be that our current particles list/table is not fully updated?

Edited April 10 by Dandav