Reply to "Comment on 'Modifying the variational principle in the action-integral-functional derivation of time-dependent density functional theory'"

TL;DR

This paper defends the original criticism of a proposed modification to the variational principle in time-dependent density functional theory, clarifying key points and reaffirming the initial objections.

Contribution

It provides a detailed rebuttal to recent claims defending the modified variational principle, reaffirming the validity of the original criticism.

Findings

The criticism of the modified variational principle remains valid.

The response clarifies misunderstandings about the original critique.

The core issues in the variational approach are reaffirmed.

Abstract

In a recent paper [Phys. Rev. A 77, 062511 (2008)], it was advocated to modify the variational principle for the action-integral functional in the Runge-Gross foundation of time-dependent density-functional theory. This was criticised in a subsequent paper [Phys. Rev. A 62, 052510 (2010)] by the present author. In a Comment [Phys. Rev. A 83, 046501 (2011)], it is argued that the criticism is unfounded. This is a response as given to the four specific points raised in the Comment, clarifying and confirming the essence of the original criticism.