From: epjb@edpsciences.org Subject: EPJ B Editorial Decision - b200017 Date: February 25, 2020 at 00:59:52 PST To: jhirsch@ucsd.edu 25/02/2020 The European Physical Journal B Our Ref. : b200017 Dear Professor Hirsch, First of all let me apologize for the delay.  It occurred because of the difficulty to find referees willing to comment on your paper.  I managed to secure two reports by internationally well known referees - both indicate that the material is - albeit interesting - not suitable for publication in EPJB (see reports enclosed). Please consider publishing elsewhere. Best regards, R. Egger Editor, EPJ_B ............................................. Report from Referee 8: Report 1: The paper discusses the dynamics of the Meissner effect. It argues that (i) conventional BCS-type theories do not explain the Meissner effect, (ii) that an effective theory involving a perfectly conducting fluid needs to be used, (iii) that this fluid does not carry charge or mass but effective mass, and (iv) that these arguments strongly support the concept of "hole superconductivity", promoted by the author since many years. I do not recommend publication of this paper as it is in my opinion strongly misleading in central aspects and has also some major weaknesses in its main lines of argument. I will not comment on the concept of hole superconductivity but try to focus on the other lines of argument. The first question is whether the claim of the author is correct that standard BCS theory does not explain the Meissner effect, i.e., the expelling of a magnetic field upon lowering of Tc. This is partially a semantic question. BCS theory is a variational theory with the goal to find the minimum of the free energy. As such, it can describe the Meissner effect in the limit when the temperature is changed so slowly, that the system remains all the time in thermal equilibrium (the author seems to acknowledge that at the beginning of the Discussion chapter but not in the rest of the paper). It can, however, not easily describe the dynamics of the transition at finite speed because the mean-field theory lacks disorder and interaction effects which are essential to establish thermal equilibrium (these effects are not discussed in this paper either). The simplest approach able to describe the dynamics, the time-dependent Ginzburg Landau theory, is dismissed by the author with the (wrong) ar gument that such an irreversible equation cannot describe a reversible process. The process is, however, only "reversible" in the ultraslow limit (as discussed in Sec XII), which is reproduced by the time-dependent GL theory. The friction term is valid only close to Tc where it effectively describes the coupling to a disordered and interacting normal component, which acts as a source for irreversible processes (the friction term does not conserve energy or (angular) momentum which are transfered to the lattice via impurities and Umklapp). The author then postulates the existence of a charge-neutral perfectly conducting fluid. If I understand right, this fluid is conducting with an infinite conductivity and furthermore also flows without friction. These are two independent properties: two quantities are flowing without friction, a highly exotic postulate. The author claims that the new quantity (besides charge) flowing without friction is "effective mass". I think that it is a major problem of this construction that effective mass is just not  conserved (Eq. (71b) stating the opposite has no justification in the paper). While there are also other issues with the paper, the two issues mentioned above are in my opinion sufficient to reject the paper. It uses a highly problematic postulate to explain a problem which does not exist in my opinion. Report from Referee 9: Report 1: The author analyzes the dynamics of the Meissner effect in superconductors using magnetohydrodynamical concepts. He claims that BCS theory is not able to explain the process by which a normal metal expels the magnetic field when becoming superconducting and points out to the unconventional theory of hole superconductivity as an alternative explanation. The problem raised in this manuscript is of great fundamental interest. It is true that a detailed description of the onset of the Meissner effect from the BCS microscopic theory doesn't exist. However, in my opinion, this does not imply that one should simply replace the conventional theory, which has been tested experimentally experimentally uncountable times, with an unconventional one which does not have much or any experimental support.   In addition, one may wonder whether the analysis presented by the authors applies to a realistic situation. It is claimed that the transition should be "reversible". However, this would require a extremely slow process and the interaction with a reservoir to maintain thermal equilibrium, an ingredient which is lacking in the author's analysis but would be essential in a fully microscopic theory. In my opinion, questioning BCS theory for the lack of description of the transition dynamics would be equivalent to question any other mean field theory of a phase transition. In summary, although the issue is of great interest neither the author approach nor its conclusions are convincing. I therefore cannot recommend this manuscript in its present form. -- EPJ Editorial Office http://www.epj.org