What are the meaning of monopole character and dipole character?

In summary, Hehl's paper discusses the concept of mass and spin in general relativity, and how they behave in the macrophysical limit. Mass is considered to have a monopole character, meaning it is always positive and additive, while spin is of dipole character and can cancel out. The statement "mass (or energy-momentum) adds up" should be used carefully, as it refers to the inertial mass represented by the energy term in the energy-momentum equation, rather than rest mass.
  • #1
xiaomaclever
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In Hehl's paper "general relativity with spin and torsion:Foundations and prospects",there is a sentence ," in the macrophysical limit, mass (or energy-momentum) adds up because of its monopole character, where as spin , being of dipole character, usually averages out." anybody who know the meanings of this sentence explains for me please. thanks.
 
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  • #2
xiaomaclever said:
In Hehl's paper "general relativity with spin and torsion:Foundations and prospects",there is a sentence ," in the macrophysical limit, mass (or energy-momentum) adds up because of its monopole character, where as spin , being of dipole character, usually averages out." anybody who know the meanings of this sentence explains for me please. thanks.

Can you give the whole paragraph so we can get the context?
 
  • #3
xiaomaclever said:
In Hehl's paper "general relativity with spin and torsion:Foundations and prospects",there is a sentence ," in the macrophysical limit, mass (or energy-momentum) adds up because of its monopole character, where as spin , being of dipole character, usually averages out." anybody who know the meanings of this sentence explains for me please. thanks.

I'm not familiar with the terminolgy as used in this context but I think what they are getting at is that spin is either up or down and nothing inbetween (it's dipole nature) and can cancel out while mass is always positive (monopole nature, even anti particles have positive mass) so it is additive.

In this context it is a bit like charge which averages out because of its dipole positive or negative nature, or is it tripole if we count neutral?

The statement "mass (or energy-momentum) adds up" has to be used with caution because the result of the energy-momentum equation is rest mass and does not add up in the normal way. A pair of photons can have non zero rest mass when considered as a total system while the individual photons that make up the system have zero rest mass. It would be better to consider the inertial mass represented by the energy term of the energy-momentum equation which is a scalar quantity which is directionless (scalar) and always adds up in the normal way in the rest frame of a closed system.
 

1. What is the difference between monopole character and dipole character?

Monopole character refers to the charge distribution in a molecule or atom, where there is only one region of positive or negative charge. Dipole character, on the other hand, refers to the presence of two regions of opposite charges within a molecule or atom.

2. How is monopole character and dipole character determined?

Monopole character is determined by the overall charge of an atom or molecule, while dipole character is determined by the difference in electronegativity between atoms within a molecule.

3. What is the significance of monopole character and dipole character in chemistry?

Monopole character and dipole character play a crucial role in determining the polarity of molecules, as well as their chemical and physical properties. They also affect the strength of intermolecular forces and the ability of molecules to interact with each other.

4. Can a molecule have both monopole character and dipole character?

Yes, a molecule can have both monopole character and dipole character. This is commonly seen in polar molecules, where there is an overall charge but also a difference in electronegativity between atoms within the molecule.

5. How can monopole character and dipole character be manipulated?

Monopole character and dipole character can be manipulated through the addition or removal of electrons, as well as by changing the types of atoms present in a molecule. These changes can alter the polarity and overall charge distribution of a molecule.

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