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  1. Lord Jestocost

    B Weinberg on the measurement problem

    The mathematical formalism of quantum theory has nothing to say regarding the actual outcome of a single measurement event; such questions are not answerd by the minimal statistical interpretation as long as one doesn't confuse the minimal statistical interpretation with the ensemble...
  2. Lord Jestocost

    I Entropic Force - Heat Transfer Mechanism

    Stretching of a rubber band (ordering) restricts the available microstates for its internal degrees of freedom, so that its thermal energy – under adiabatic conditions – has to be redistributed among a lesser number of degrees of freedom. Reversely, when a rubber band is allowed to relax...
  3. Lord Jestocost

    I Does the postulate of equal a priori probability apply only to equilibrium?

    Personally, I prefer the following statement: “If an isolated system is found with equal probability in each accessible microstate, then it is in equilibrium. Starting with this distribution, it stays that way. This is what we mean by thermal equilibrium.” (from the Lecture Note about the...
  4. Lord Jestocost

    B Energy of an Electron

    When an electron is excited from the valence band to the conduction band, its total energy is changed by ##E_C(\vec k_C)-E_V(\vec k_V)##, where ##\vec k_V## and ##\vec k_C## are the wave vectors (crystal momenta) of the electron in its initial valence band state (just before the transition) and...
  5. Lord Jestocost

    A Metal Semiconductor Contact

    "Since the density of free carriers is very high in a metal, the thickness of the charge layer in the metal is very thin. Therefore, the potential across the metal is several orders of magnitude smaller than that across the semiconductor, even though the total amount of charge is the same in...
  6. Lord Jestocost

    B Energy of an Electron

    In the free electron approximation the potential energy contribution is assumed to be zero.
  7. Lord Jestocost

    I Why do we need to supply energy to a biological body to keep entropy decreasing?

    Biological organisms are open systems which exchange permanently matter and energy with the environment to maintain a so-called nonequilibrium steady state. They are self-organizing dissipative structures: “…the maintenance of order in actual living systems requires a great number of metabolic...
  8. Lord Jestocost

    A Metal Semiconductor Contact

    In an ideal case, the work function of the metal and the electron affinity of the semiconductor are material properties.
  9. Lord Jestocost

    B Energy of an Electron

    "The band structure of a material is (essentially), a description of the way the total energy of electronic states varies as a function of their quantum number. k = (kx ,ky ,kz ). In other words, the band structure of a material is a statement of the total energy relationship E(k), which is in...
  10. Lord Jestocost

    A Metal Semiconductor Contact

    a) Even if some electrons are transferred from the n-type semiconductor to the metal, the Fermi energy of the metal doesn’t change because of the extremely high electron density in metals. b) The Schottky barrier - a barrier for electrons to move from the metal to the semiconductor - is the...
  11. Lord Jestocost

    Phase transition between two phases with different Cv

    When dealing with a second order phase transition, the entropy is continuous at ##T_c## (it has a kink as the heat capacities of both phases differ from each other). See the figures on page 20 in [PDF] Phase Transitions and Phase Diagrams - Virginia The temperature dependence of the entropy in...
  12. Lord Jestocost

    I What is really that density matrix in QM?

    "Is it not good to know what follows from what, even if it is not really necessary FAPP? Suppose for example that quantum mechanics were found to resist precise formulation. Suppose that when formulation beyond FAPP is attempted, we find an unmovable finger obstinately pointing outside the...
  13. Lord Jestocost

    I Is this another Maxwell's demon?

    In order to count molecules, the demon must be able to see them. He is in a container in equilibrium at constant temperature, where the radiation must be that of a blackbody. As it is impossible to see anything in the interior of a black body (the demon has the same temperature), he needs...
  14. Lord Jestocost

    I What is really that density matrix in QM?

    Bruce Rosenblum writes in "Quantum Enigma" (by Bruce Rosenblum and Fred Kuttner): “I (Bruce) shared a taxi and conversation with John Bell in 1989 on the way to a small conference in Erice, Sicily, which focused on his work. At the conference, with wit, and in his Irish voice, Bell firmly...
  15. Lord Jestocost

    I What is really that density matrix in QM?

    The distinction is a fundamental physical fact: A superposition remains a superposition! “Decoherence is, formally, never complete. There always remain exponentially small non-diagonal terms in the reduced density matrix, reminding us that an initial pure state remains pure according to basic...
  16. Lord Jestocost

    A Shouldn't the shape of a semiconductor laser be planar instead of conical?

    See Fig. 6 in https://pe2bz.philpem.me.uk/Lights/-%20Laser/Info-999-LaserCourse/C04-M06-DiodeLaserPowerSupplies/mod04_06.htm "The beam emitted from a semiconductor laser typically has an elliptical spatial profile, as illustrated in Figure 6. The profile is caused by diffraction. In the...
  17. Lord Jestocost

    Phase transition between two phases with different Cv

    The next question is: Is there a thermodynamic function which shows a characteristic behavior at the transition temperature ##T_c## and which can be related to the heat capacities in both phases?
  18. Lord Jestocost

    B Entanglement & Wave Function Collapse

    For me, ideas of "superluminal signals" or "spooky actions at a distance" were always nonsensical ideas and helpless attempts to “explain” something which cannot be explained. But, what have "superluminal signals" or "spooky actions at a distance" to do with the collapse postulate. You are...
  19. Lord Jestocost

    B Entanglement & Wave Function Collapse

    In my comment #53, I have merely cited remarks by Ghirardi and Dirac which are related to the wave-packet reduction postulate. Referring to comment #53, you start your comment #59 with “But that's highly problematic”. I do not have any clue what’s now highly problematic. The wave-packet...
  20. Lord Jestocost

    B Entanglement & Wave Function Collapse

    That’s not problematic in case one accepts quantum non-separability. Franck Laloë, in “Do We Really Understand Quantum Mechanics?”: “The idea is that different quantum systems, when they have interacted in the past, no longer have in general their own physical properties; they are both part of...
  21. Lord Jestocost

    B Entanglement & Wave Function Collapse

    State reduction is a fundamental postulate and part of the formalism. As Giancarlo Ghirardi puts it in the entry “Collapse Theories” on the “Stanford Encyclopedia of Philosophy” (https://plato.stanford.edu/entries/qm-collapse/) : “The fact that when the measurement is completed one can make...
  22. Lord Jestocost

    B Is the concept of "wave function collapse" obsolete?

    In case you would recombine "both beams", you would find every particle in the pure |+x> state again. Nothing is randomnized.
  23. Lord Jestocost

    Phase transition between two phases with different Cv

    What does it mean for the order of a phase transition if there is no latent heat generated at the transition temperature Tc?
  24. Lord Jestocost

    B Is the concept of "wave function collapse" obsolete?

    What the heck do you want to tell? When you partially block the beam in a say z-oriented Stern-Gerlach apparatus which is fed with a beam of say |+x> polarized particles, you simply acquire a “which path information”. That’s at the end a measurement leading to a “state reduction” to say |+z> or...
  25. Lord Jestocost

    B Is the concept of "wave function collapse" obsolete?

    This statement is misleading. Quantum theory is, as termed by Schwinger, a causal, statistically deterministic theory. That’s all. But quantum theory has nothing to say regarding the outcome of a single measurement event; there exists no connection between quantum theory and individual...
  26. Lord Jestocost

    Quantum Interpretations of QM in different countries

    Otto Robert Frisch in “What Little I Remember”: "I remember an occasion when after a lengthy discussion on the fundamental problems of quantum theory a visitor said 'It makes me quite giddy to think about these problems.' Bohr immediately rounded on him and said 'But, but, but...if anybody says...
  27. Lord Jestocost

    B Is the concept of "wave function collapse" obsolete?

    Freeman Dyson: "When new knowledge displaces ignorance, the wave-function does not collapse; it merely becomes irrelevant." https://www.edge.org/response-detail/25350
  28. Lord Jestocost

    I Why randomness means incomplete understanding

    To my mind, there is need to more profound thinking. The onsets of individual clicks in a counter seem to be totally lawless events, coming by themselves and thus being uncaused. Or can one denote a cause which compels these individual effects?
  29. Lord Jestocost

    What is the heat of combustion of 1 kg carbon dioxide w/ magnesium?

    You must clearly distinguish between the standard molar reaction enthalpy, ΔrH°, and the standard molar enthalpy of formation (or standard molar heat of formation), ΔfH°. ΔrH° = -810.1 kJ/mol is the standard molar reaction enthalpy for the reaction 2Mg(s) + CO2 ---> 2MgO(s) + C(s) . The...
  30. Lord Jestocost

    A Is quantum theory a microscopic theory?

    A way out might be that we at first accept that this what we call 'reality' is just a state of mind. https://www.theguardian.com/science/blog/2009/mar/17/templeton-quantum-entanglement
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