Hello,(adsbygoogle = window.adsbygoogle || []).push({});

In the context of QFT, I do not understand the statement:

##\frac{\delta \phi(x)}{\delta \phi(y)}=\delta (x-y)##

I understand the proof which arises from the definition of the functional derivative but I do not get its meaning. From what I see is generalizes ##\frac{\partial q_i}{\partial q_j}=\delta_{ij}## which I am not sure to understand either.

Would somebody be kind enough to explain me ?

I realize this is not a question concerning QFT only but it is where I have the better chance to find a good answer since it is fundamental in that field.

Best,

VM

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Infinitesimal field variation

Loading...

Similar Threads for Infinitesimal field variation |
---|

I There are no particles, only fields! |

A Vacuum in QFT: Fock space or effective potential? |

I What's the effect of E-field for an electron in a solid? |

A Cause and effect and quantum field theory |

A Is irreducibility justified as a Wightman axiom? |

**Physics Forums | Science Articles, Homework Help, Discussion**