Articles from the Institute Letter

Additional articles from new and past issues of the Institute Letter will continue to be posted over time and as they become available.

by Yvonne Chiu

A wounded German soldier lighting a cigarette for a wounded British soldier at a British field hospital during the Battle of Épehy, near the end of the First World War (1918)
A wounded German soldier lighting a cigarette for a wounded British soldier at a British field hospital during the Battle of Épehy, near the end of the First World War (1918) (Photo: Lt. Thomas K. Aitken, British Army photographer/Imperial War Museums)

‘Live and Let Live’ as a Representative Element of War

Images that convey the essence of war are more likely to resemble the frenzied, merciless, mutual slaughter between the Aegeans and the Trojans as told in The Iliad, the rapes depicted in Goya’s The Disasters of War, the torture portrayed in The Battle of Algiers, or the indiscriminate napalm bombing in Vietnam dramatized in Apocalypse Now. It is commonly believed—and for good reason—that morality and civilization are inevitably forgotten in war, as participants become desperate to survive, get caught up in the bloodlust, or lose touch with their humanity. There is truth to that, so it might be surprising to think of banning hollow point bullets (Hague Convention, 1899) or regulating prisoner-of-war treatment (from the 1648 Peace of Westphalia through the 1949 Geneva Conventions) as simultaneously capturing an essential element of warfare, but in fact they represent a significant component of war, which is cooperation between enemies.

Some of the more amazing stories of cooperation in warfare come from the trenches of World War I. During the Christmas truces in 1914, and to a lesser extent in 1915, not only did 100,000 British and German soldiers in WWI unofficially stop fighting, but in some places in Belgium, German soldiers who decorated their trenches with candles and trees and sang carols were met with British soldiers singing in kind; eventually, the two sides mingled in No Man’s Land, exchanging gifts, food, and souvenirs, and even engaging in short, casual football games.

In addition to ad hoc cooperation on a shared holy day, opposing trenches spontaneously developed a longer-lived system of timed shellings to allow the other side to anticipate and avoid their impact. While trench warfare was a large part of the WWI experience, it is not particularly interesting militarily. Rather, it is noteworthy for what fighting did not happen. This “live and let live” system has been recounted in marvelous detail by Tony Ashworth (Trench Warfare 1914–1918). That reciprocal exchange—of minimization of injury and death—took different forms during the war: truces lasted anywhere from a few minutes to several months; some were explicit agreements between fraternizing soldiers in close quarters, while others were indirect (due to legal sanctions), over long distances, and involving large numbers of people. There were numerous reports of people walking openly above trenches; unrestricted movement in and out of the trenches; Germans frying sausages and photos of Brits frying bacon in the trenches, despite the fact that smoke from the fires would have attracted gunfire on active fronts; and descriptions of “quiet” fronts, where there were no ammunition shortages. In some trenches, people hunted and retrieved small game, harvested vegetables, kept milking cows for fresh milk, and had pianos and books.

Prospects in Theoretical Physics at the Institute for Advanced Study (Photo: Alexandra Altman)

The Institute’s thirteenth annual Prospects in Theoretical Physics (PiTP) summer program for graduate students and postdoctoral scholars, which focused on string theory, was truly extraordinary in that it overlapped with Strings 2014. This is one of the field’s most important gatherings, which the Institute hosted with Princeton University, convening international experts and researchers to discuss string theory and its most recent developments. Six hundred attendees gathered for Strings 2014, which made it one of the largest Strings conferences since their inception in 1995.

Strings 2014 talks, which covered topics from B-mode cosmology and the theory of inflation to quantum entanglement, the amplituhedron, and the fate of spacetime, may be viewed at The program for PiTP and videos of its string theory talks may be viewed at

As part of the PiTP program, the Institute showed a screening of Particle Fever, a new film that follows six scientists, including the Institute’s Nima Arkani-Hamed, during the launch of the Large Hadron Collider and fortutiously captures the discovery of the Higgs particle. Peter Higgs, who predicted the existence of the particle fifty years ago, gave one of his first seminars on the topic at the Institute in 1966.


Exploring the Arguments of Independence

The following text is excerpted from Our Declaration: A Reading of the ­Declaration of Independence in Defense of Equality (Liveright Publishing Corporation, 2014) by Danielle Allen, UPS Foundation Professor in the School of Social Science.

The Declaration of Independence matters because it helps us see that we cannot have freedom without equality. It is out of an egalitarian commitment that a people grows—a people that is capable of protecting us all collectively, and each of us individually, from domination. If the Declaration can stake a claim to freedom, it is only because it is so clear-eyed about the fact that the people’s strength resides in its equality.

The Declaration also conveys another lesson of paramount importance. It is this: language is one of the most potent resources each of us has for achieving our own political empowerment. The men who wrote the Declaration of Independence grasped the power of words. This reveals itself in the laborious processes by which they brought the Declaration, and their revolution, into being. It shows itself forcefully, of course, in the text’s own eloquence.

When we think about how to achieve political equality, we have to attend to things like voting rights and the right to hold office. We have to foster economic opportunity and understand when excessive material inequality undermines broad democratic political participation. But we also have to cultivate the capacity of citizens to use language effectively enough to influence the choices we make together.


by Clyde Plumauzille

Professor Joan Scott at the School of Social Science’s twenty-fifth anniversary conference in 1997,  “25 Years: Social Science and Social Change”
Professor Joan Scott at the School of Social Science’s twenty-fifth anniversary conference in 1997, “25 Years: Social Science and Social Change” (Photo: Randall Hagadorn)

Revealing Implicit Structuring Norms and Challenging Categories of Difference

Critique will be the art of voluntary insubordination.”1 Epigraph to her essay ­”History-writing as Critique,”2 this quote from Michel Foucault is the key to understanding the epistemological journey of the American historian Joan W. Scott. Professor Emerita at the Institute for Advanced Study in Princeton, Scott is the author of numerous works on gender, feminism, and citizenship. A prolific and dynamic scholar, she has gone from studying social history to studying the history of women and then, in the 1980s, to studying the history of gender, becoming one of the first theorists in the field. With each shift in her historiographical focus, Scott has found the material needed to fuel her critical thought and shed light on the blind spots of social systems from the time of the French Revolution until the present day. Always on the lookout for history’s paradoxes, she has spent her entire career combatting the naturalization of differences and inequalities that stem from these contradictions.

As a historian and critical feminist, she has called for the concepts used in the social sciences to remain categories of critical intervention within political and academic debates. That’s why, from her seminal article “Gender: A Useful Category of Analysis,” published in 1986, to the recent publication in France of her book De l’utilité du genre in 2012, Scott has continued to highlight the political, social, and even imaginary issues that can only be understood through the conceptualization of sexual difference.3 To that end, she has zeroed in on French republican universalism, making it her preferred field of research, and has regularly weighed in on the public discussions surrounding its paradoxes. The politicization of sexual issues in France during the 1990s and the debates surrounding parité, domestic partnerships, and the wearing of Islamic headscarves have allowed her to reflect upon and discuss the reformulation of the republican contract by using real-life examples.

Now that “gender theory” has fallen under attack in France, denounced by its critics as an ideology that destroys the natural order and upsets the political and social balance, it seems fitting, if not crucial, that we take a look back on the ever-changing thoughts of a historian who has contributed greatly to the introduction of the concept of gender within the field of historiography.


by Shiraz Minwalla

Shiraz Minwalla has uncovered an unexpected connection between the equations of fluid and superfluid dynamics and  Einstein’s equations of general relativity.
Shiraz Minwalla has uncovered an unexpected connection between the equations of fluid and superfluid dynamics and Einstein’s equations of general relativity. (Photo: McKay Savage)

How the Movement of Water Molecules Corresponds to Ripples in Spacetime

There is an interesting connection between two of the best-studied nonlinear partial differential equations in physics: the equations of hydrodynamics and the field equations of gravity.

Let’s start with a brief review of hydrodynamics. At the microscopic level a tank of water is a collection of, say, 1025 molecules that constantly collide with one another. The methods of physics may be used to model this collection of water molecules as follows: we set up equations that track the position and momentum of each of the water molecules and predict their time evolution. These conceptually complete equations have of order 1025 variables and so are clearly too difficult to handle in practice.

Does it then follow that tanks of water cannot be usefully studied using the methods of physics? As every plumber knows, this conclusion is false: a useful description of water is obtained by keeping track of average properties of water molecules, rather than each individual molecule.

Think of a tank of water as a union of non-overlapping lumps of water. Each lump is big enough to contain a large number of molecules but small enough so that gross macroscopic properties of the water (energy density, number density, momentum density) are approximately uniform. The fundamental assumption of hydrodynamics is that under appropriate conditions, all the “average” properties of any lump are completely determined by its conserved charge densities (in the case of water, molecule number density, energy density, and momentum density). In particular, the conserved current for molecule number jµ and the conserved current for energy and momentum Tµν are themselves dynamically determined functionals of local thermodynamical densities in a locally equilibrated system (fluctuations away from these dynamically determined values are suppressed by a factor proportional to the square root of the number of molecules in each lump). The equations that express conserved currents as functionals of conserved densities are difficult to compute theoretically but are easily measured experimentally and are known as constitutive relations.

When supplemented with constitutive relations, the conservation equations ∂µ jµ =0, and ∂µ Tµν=0(2) turn into a well-posed initial value problem for the dynamic of conserved densities. They are the equations of hydrodynamics. Let me reemphasize that the effect of the ignored degrees on the evolution of conserved densities is inversely proportional to the square root of the number of molecules in a lump, and so is negligible in an appropriate thermodynamic limit, allowing the formulation of a closed dynamical system for conserved densities.

My research concerns how the equations of hydrodynamics pop up in an apparently completely unrelated setting: in the study of the long wavelength dynamics of black holes governed by Einstein’s equations with a negative cosmological constant.

Einstein’s gravitational equations describe the dynamics of the geometry of spacetime. The ripples of spacetime (gravitational waves) have interesting dynamics even in the absence of any matter. For most of this article, I will be referring to Einstein’s equations in the absence of matter.