Stephen Parrott

picture of Stephen Parrott in Nevada
I retired in 2002.

Please do not send mail to the University, as it may be considerably delayed.
Email sent to my university account will probably be deleted unread;  there is too much spam to delete by hand, so I delete everything unless I'm expecting a message.

For contact information, click here.

Click on the next link for my  bibliography.

Here for pages of  reviews of  books and papers.  (The "papers" page has become a sort of blog.)

Essays:  Over the years I have written essays on topics which have puzzled me and put them on the "papers" page.
                As the page grew, the essays became more and more difficult to locate.
                Following is a list with brief descriptions.

                "Restoring the quantum state after a measurement"

                        According to current quantum theory, a measurement applied to a system in a given state
                    usually changes the state.  The problem addressed is whether it is possible to recover
                    the initial, premeasurement state.  This is impossible for nontrivial projective measurements,
                    but can be possible for the more general so-called POVM measurements.  The essay discusses
                    when it is possible and how to do it.  It also questions some misleading statements in the literature
                    on this problem.

                 "Analysis of the famous experiment of Grangier, Roger, and Aspect supposedly establishing the existence of the photon"

                         This 1986 experiment is frequently cited as establishing the existence of the photon.  The analysis presented in the essay 
                   leads to the opposite conclusion:  if the photon hypothesis it true, then there is a vanishing  probability
                   of obtaining the experimental results.  

                         This does not mean that the photon hypothesis is wrong (and I doubt that it is wrong), only that the experiment
                    is inconsistent with it.  The essay also discusses in less detail an experiment by an undergraduate group Thorn, et al., 
                    which obtains results consistent with the photon hypothesis.  The results of Thorn, et al. differ by an order of magnitude 
                    from those of Grangier, Roger, and Aspect (GRA).  Despite characterizing the GRA experiment  as "an experimental tour-de-force,
                    Thorn, et al.,  never mentions this inconsistency!  

                        For me, the interest in the essay is how  the GRA experiment came to be regarded as definitively establishing
                    the existence of the photon.  For about 30 years, seemingly nobody noticed the discrepancy.  It makes me wonder
                    how trustworthy are claims about modern physics experiments (not just photon experiments).  

                "A second look at P. Riley's 'On the probability of  occurrence of extreme space weather events' "

                    P. Riley's 2012 paper "On the probability of occurrence of extreme space weather events" concludes that the probability
                of a geomagnetic storm as bad as the worst known (the so-called "Carrington event" of 1859) in the next decade is on
                the order of 12%. Given that such a storm might cause trillions of dollars in damages, this is alarmingly high.  
                 This essay points out some surprising anomalies in Riley's data and analysis.  The anomalies are so serious that
                I would go so far as to say that there is no reasonable scientific basis for the 12% figure.  No one can say with
                any reasonable degree of certainty what the actual probability is, but my personal estimate would be at least an order of magnitude lower.   

Following is a link to my personal website .

Recent revisions of the papers page:   

                            October 27, 2013.  An essay entitled "Restoring the quantum state after a measurement" was added to the
                                   October 23 entry on the "papers" page.
 The October 27 entry reports on the nearly final results of
                                   two years of effort to obtain correction in the literature of erroneous papers of Dressel and Jordan.                     

                           December 6: 2013.  A recent paper of Emerson, Serbin, Sutherland, and Veitch is recommended for
                                     its transparent presentation of the Pusey/Barrett/Rudolph result.

                           February 9, 2014.  (1)  Reservations are expressed about a much-discussed paper   "Direct  measurement of the
                                    quantum  wavefunction" by Lundeen, Patel, Stewart, and Bamber.  
                                    (2)  It looks as if the Dressel/Jordan affair may finally be at an end.   The final results and how they reflect on
                                           the standards of three mainstream journals (Physical Review Letters, Journal of Physics A, and Physical
                                            Review A) are described.

                            July 25, 2014.   A statistical analysis is discussed of a famous paper of Grangier, Roger, and Aspect.  This paper
                                       is widely taken as establishing the existence of the photon.  It turns out that the data presented in the
                                       paper actually reject the hypothesis of the existence of the photon at nearly the 100% signficance
                                       level.  (Presumably, the problem lies with the data rather than the hypothesis.)

                            August 2, 2014.  A preliminary critical analysis of a paper in Space Weather, "On the probability of occurrence of extreme
                                        space weather events" by P. Riley, is posted on the papers page in order to solicit comments.   This paper estimates the probability
                                        of occurrence in the next decade of a solar storm which potentially could knock out power grids for months at
                                        a surprisingly high 12%, an estimate which has been widely disseminated in the popular press.  

                            August 4, 2014.  A recent paper of Aharonov, et al., is entitled "The quantum pigeonnole principle and the nature of
                                        quantum correlations".   The classical pigeonhole principle states that if you try to put three pigeons in two
                                        pigeonholes, at least two of the pigeons have to go in the same hole.  The paper claims :  "...we show that
                                        in quantum mechanics, this is not true!".   An article commenting on this paper is posted on the papers page.

                            August 25, 2014.  The preliminary analysis of the Riley paper mentioned in the August 2 entry above has been
                                        replaced by a 3-page "Comment" paper, which is a summary of a 15-page analysis.  On the papers page, of course.

                            August 30, 2014 . Replaced  on the August 4, 2014 entry of the  papers page the original Comment on the Aharonov, et al.,
                                        article on the pigeonhole principle with a new Version 2.  The exposition is expanded and a bad repeated typo is corrected.

                            January 14, 2015  Posted  on the papers  page a 30-page reanalysis of  Riley's paper "On the probability of occurrence of
                                        extreme space weather events"  (see Aug. 2 and 25, 2014 entries above).  Included is the fate of my "Comment" paper
                                        submitted to the journal Space Weather .

                            September 22, 2015:  Posted on the papers page a letter disagreeing with the interpretation of an experiment reported in:

                                                "NMR simulation of Quantum Pigeonhole Effect" by Anjusha V.S., Swathi S. Hegde, and T.S. Mahesh,

                                        This paper claims to experimentally verify a quantum violation of the classical "pigeonhole principle" (see Aug. 4, 2014 entry).
                                        I have no reason to doubt the experimental results, but disagree with the authors' interpretation of them.   

                            September 6, 2016.  Posted on the papers page Version 3 of  the comment on the Aharonov, et al., paper on
                                         the quantum pigeonhole principle.   The only change from Version 3 is the replacement of  the word "different" in one sentence
                                         with the intended "same".  All links to this Comment should now point to Version 3.

                            October 31, 2016.  On the papers page:
                                        (i)  Comments on the recent ascension of Pierre Meystre to Chief Editor of  the Physical Review journals.
                                        (ii) Remarks on a new paper which I just posted on the arXiv:  "Quantum measurements need not conserve energy:
                                                relation to the Wigner-Araki-Yanase theorem"

Recent revisions of the books page:

                                        July 27, 2016:  Added two reviews, of
                                                        The Geometry of Physics  by  Theodore Frankel ,  and

                                                        Curvature in Mathematics and Physics  by  Shlomo Sternberg