### When & Where?

- November 7–8, 2022
- 215 Humphrey (Wilkins Room), University of Minnesota, Twin Cities; and online, via Zoom
- Registration is required, but free. Registrants attending online will receive a Zoom link via email.
- Workshop dinner at 7 PM, Nov. 7, venue TBA. Cost will be ~$80. Registrants who indicate an interest in attending the dinner will receive information via email regarding payment methods.
- Current UMN Covid protocols will be in effect.

### What & How?

### Who? (Speakers)

### More on When (Program)

#### Monday, November 7, 2022

Time |
Event |
---|---|

9:15–9:30 | Opening Remarks (Alan Love) |

9:30–10:30 | Charlotte Werndl (Salzburg): Phase Transitions: Boltzmann versus Gibbs |

10:30–10:45 | Coffee Break |

10:45–11:45 | Lena Zuchowski (Bristol): From Randomness to the Arrow of Time |

11:45–12:00 | Coffee Break |

12:00–1:00 | Giovanni Valente (Poli Milano): Taking up Statistical Thermodynamics: Equilibrium Fluctuations and Irreversibility |

1:00–2:30 | Lunch Break |

2:30–3:30 | Clayton Gearhart (St. John’s): “Astonishing Successes”; “Bitter Disappointment”: Physics Textbooks and the Old Quantum Theory |

3:30–3:45 | Coffee Break |

3:45–4:45 | Michel Janssen (UMN): Getting Right to the Heart of Matters (Counting Crows in Omaha) |

4:45–5:00 | Coffee Break |

5:00–6:00 | Margriet van der Heijden (Eindhoven/AUC): Tatiana Afanassjewa and Paul Ehrenfest – A Cosmopolitan Oasis in Provincial Leiden |

7:00 | Workshop Dinner |

#### Tuesday, November 8, 2022

Time |
Event |
---|---|

9:00–10:00 | Wayne Myrvold (Western): Two Sciences Called “Thermodynamics” |

10:00–10:15 | Coffee Break |

10:15–11:15 | Samuel C. Fletcher (UMN): The Thermodynamics of Compact Astrophysical Objects |

11:15–11:30 | Coffee Break |

11:30–12:30 | Bryan W. Roberts (LSE): Geometric Thermodynamics and Black Holes |

12:30–1:00 | Closing Remarks |

### More on What (Abstracts)

#### Samuel C. Fletcher (UMN): The Thermodynamics of Compact Astrophysical Objects

I discuss the prospects of extending black hole thermodynamics to any compact astrophysical object and its implications for the nature of thermodynamics.

#### Clayton Gearhart (St. John’s): “Astonishing Successes”; “Bitter Disappointment”: Physics textbooks and the old quantum theory

How do physics textbooks treat flawed theories? With the old (pre-Heisenberg and Schroedinger) quantum theory, textbook authors were faced with a theory that often worked, but just as often did not. The title of my talk is taken from Fritz Reiche’s 1921 textbook, but there are many other early textbooks that treat quantum theory, from well before 1920 to the 30s and 40s. Even after the appearance of modern quantum mechanics, textbook authors continued to treat the old quantum theory —sometimes in considerable detail. I give an introduction to this surprising and interesting literature.

#### Michel Janssen (UMN): Getting Right to the Heart of Matters (Counting Crows in Omaha)

In an obituary for Paul Ehrenfest (1880–1933), Albert Einstein praised his dearly departed friend and colleague for his “unusually well developed faculty to grasp the essence of a theoretical notion, to strip a theory of its mathematical accouterments until the simple basic idea emerged with clarity.” In this talk, I’ll give a few examples of how he pulled this off and argue that Ehrenfest is best understood not so much as a theoretical physicist but as a philosopher of physics *avant la lettre*.

#### Wayne Myrvold (Western): Two Sciences Called “Thermodynamics”

It has been occasionally remarked, but insufficiently appreciated, that there are two distinct sorts of endeavour that have gone by the name of “thermodynamics”. The first, which is in line with how the founders of the subject thought of it, is a theory about how agents with limited means of manipulation and limited access to information about a system can exploit its physical properties to achieve specified ends. On this conception, which I have elsewhere called the “Maxwellian view”, thermodynamics is not a theory of basic or fundamental physics, but is, rather, a *resource theor*y (or family of resource theories), akin to quantum information theory. The second, which I will call the “Planckian view”, thermodynamics has been severed from its roots in technological considerations, and is a theory about the bulk properties of macroscopic matter. The distinction between these two views makes a difference for the relation between thermodynamics and statistical mechanics. On the Planckian view, the relation should be one of reduction, and it is a matter of consternation that this supposed reduction is anything but straightforward. On the Maxwellian view, it is perfectly natural and appropriate for conceptions alien to physics proper (such as the notion of information) be brought to bear in discussing the relation of thermodynamics to the underlying physics. I will argue that many of the philosophical conundrums associated with thermodynamics arise from a failure to distinguish between Maxwellian and Planckian thermodynamics.

#### Bryan W. Roberts (LSE): Geometric thermodynamics and black holes

We formulate and defend an interpretation of what it means to be an equilibrium thermodynamic system, as a Gibbs-inspired geometric theory with models given by contact manifolds. This allows one to state a precise sense in which black holes are “really thermal”, in spite of the fact that some of their thermodynamic properties are very unusual.

#### Margriet van der Heijden (Eindhoven/AUC): Tatiana Afanassjewa and Paul Ehrenfest – A cosmopolitan oasis in provincial Leiden

In September 1912 a small company arrived at Leiden’s railway station. The 32-year old theoretical physicist Paul Ehrenfest, 36-year old mathematician and physicist Tatiana Afanassjewa, and their almost seven-year old daughter Tatiana were followed by a nanny carrying her belongings in a bundle and holding toddler Galenka Ehrenfest by the hand. They were happy to come to this relatively small and provincial town: after many years of – often desperately – seeking a stable position at a university, Ehrenfest had been offered a prestigious post here. He was to become the successor to the well-known theoretical physicist and Nobel Laureate Hendrik Lorentz.

In the years thereafter Ehrenfest and Afanassjewa built a large house at Witte Rozenstraat 57, which soon turned into a cosmopolitan oasis for famous colleagues like Bohr, Einstein, Meitner, Oppenheimer, Pauli, and plenty other international guests. Students who attended the lively debates went on to become influential scientists themselves, while Afanassjewa’s discussions with Dutch mathematics teachers triggered the reform of mathematical education in the Netherlands. Margriet van der Heijden will explore the influence of Ehrenfest, raised in Vienna, and of Afanassjewa, raised in Petersburg, on the scientific landscape in the Netherlands and elsewhere.

#### Giovanni Valente (Poli Milano): Taking up Statistical Thermodynamics: Equilibrium Fluctuations and Irreversibility

The reduction of thermodynamics to statistical mechanics is a much discussed case-study in philosophy of physics. Based on the Generalised Nagel-Schaffner model, it would be accomplished if one finds a corrected version of classical thermodynamics that can be strictly derived from statistical mechanics at the microscopic level. That is the sense in which, according to Callender (1999, 2001), one should not take thermodynamics too seriously. Arguably, the sought-after revision is given by statistical thermodynamics (cfr. Batterman 2001, Dizadji-Bahmani et al. 2010), intended as a macroscopic theory equipped with a probabilistic law of equilibrium fluctuations. In this talk I critically evaluate this proposal. The upshot is that, while statistical thermodynamics enables one to re-define equilibrium so as to agree with Boltzmann statistical-mechanical entropy, it does not provide a definitive solution to the problem of modelling macroscopic irreversibility at the microscopic level.

#### Charlotte Werndl (Salzburg): Phase Transitions: Boltzmann versus Gibbs

There are two main frameworks in statistical mechanics: Boltzmannian statistical mechanics and Gibbsian statistical mechanics. In this talk we will look at how Boltzmannian and Gibbsian statistical mechanics can conceptualise phase transitions. We will show that, in calculations, the results for Gibbsian statistical mechanics and Boltzmannian statistical mechanics do not always coincide. We will discuss the implication of these results on the relationship between Boltzmannian and Gibbsian statistical mechanics.

#### Lena Zuchowski (Bristol): From Randomness to the Arrow of Time

The talk will trace the roots of different versions of the entropy-based Arrow of Time. It will be demonstrated that there are at least three different derivational routes to an Arrow of Time: (i) starting from the Thermodynamic Entropy and inductively deriving the Empirical 2nd Law to ground the Empirical Arrow of Time; (ii) starting from a notion of randomness, which acts as a desiderata on the definition of Boltzmann and Gibbs Entropy, from which one can deductively derive the Statistical 2nd and then ground either (ii) the Universal Statistical Arrow of Time or (iii) the Local Statistical Arrow of Time. Each of the three Arrows has different epistemic advantages and disadvantages: prominently, the Empirical Arrow of Time provides a straightforward definitional grounding of the direction of time; in contrast, the two statistical Arrows of Time have higher explanatory potentials, but their derivation requires the introduction of additional assumptions.

### Acknowledgements

Funding provided by:

- The Department of Philosophy, University of Minnesota, Twin Cities
- The Minnesota Center for Philosophy of Science