nLab Editing quark bag model

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#### Quantum Field Theory
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[[!include AQFT and operator algebra contents]]
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#### Fields and quanta
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[[!include fields and quanta - table]]
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#Contents#
* table of contents
{:toc}

## Idea

In [[nuclear physics]] ([[quantum chromodynamics]]) the _bag model_ is an _ad hoc_ [[effective field theory|effective]] [[model (in theoretical physics)|model]] of [[quark]] [[confinement]] in [[hadrons]], assuming literally that the [[quarks]] are constrained within an impenetrable membrane, the "bag".

The _[[Cheshire cat principle]]_ is the observation that this "bag" is not actually [[observable]].

The Cheshire Cat Principle follows in [[holographic QCD]], where the baryons are holographically realized as [[Skyrmions]]:

> The [[Skyrmion]] is the ultimate [[soliton|topological]] [[quark bag model|bag model]] with zero size bag radius, lending further credence to the [[Cheshire cat principle]]. ([Nielsen-Zahed 09](#NielsenZahed09))

## Related concepts

* [[QCD]]

* [[confinement]]

* [[Cheshire cat principle]]

[[!include effective field theories of nuclear physics -- contents]]

## References

### General

Textbook account:

* [[Ulrich Mosel]], *Bag Models of Hadrons* ([doi:10.1007/978-3-662-03841-3_16](https://doi.org/10.1007/978-3-662-03841-3_16)), Chapter 16 in: *Fields, Symmetries, and Quarks*, Springer 1999 ([doi:10.1007/978-3-662-03841-3](https://link.springer.com/book/10.1007/978-3-662-03841-3))