Exploring collective interactions of matter and antimatter

STRIP AWAY ELECTRONS FROM THEIR ATOMS and you get a plasma — a collection of negatively charged electrons and positively charged ions. But at high energies around compact cosmic objects such as black holes, quasars and pulsars, curious plasmas may form that, instead of ions, contain positrons, the antimatter counterparts of electrons.

Scientists are searching for ways of distinguishing this type of plasma from others, both in astrophysical environments and in laboratories on Earth. Julia Mikhailova, an assistant professor of mechanical and aerospace engineering, and Matthew Edwards, a graduate student in her lab, together with Professor of Astrophysical Sciences Nathaniel Fisch, found that, contrary to earlier claims, an electron-positron plasma would scatter some wavelengths of light surprisingly intensely via a process called Brillouin scattering.

This fundamental insight into the unusual behavior of matter-antimatter plasmas, published in the journal Physical Review Letters Jan. 8, 2016, may help to find such plasmas in space, or validate methods for creating them in the lab. The work was funded in part by the National Science Foundation and the National Nuclear Security Administration. –By Bennett McIntosh

Researcher probes the secret life of electrons

ELECTRONS DART within and between atoms far too quickly for current imaging techniques to observe their motion. To capture fast-moving objects without a blur, a photographer can use a camera flash to light up a scene for an instant. Julia Mikhailova, an assistant professor of mechanical  and aerospace engineering, hopes to capture electron motion in a similar way, but her camera flash must last only a few attoseconds — just millionths of a trillionth of a second.

Mikhailova and her team use lasers and plasmas, which are collections of charged particles, to create attosecond pulses of light. “With these pulses one can observe the action inside atoms and molecules,” Mikhailova said. These observations could help researchers predict electron behavior, leading to a better understanding of everything from chemical reactions to superconductivity.

Lasers cannot by themselves produce such brief pulses. Instead, scientists scatter high-powered laser light off a stream of gas. Too much energy from the laser, however, can strip the electrons in the gas from their atoms to make a plasma that no longer scatters light in the right way.

Mikhailova and her team, with funding from the National Science Foundation, are taking a different approach. Instead of using a gas target, they aim a much higher-powered laser at a solid glass disc, creating a dense plasma at its surface. The laser light — an oscillating electromagnetic field — accelerates the electrons in the plasma toward nearly the speed of light. At these speeds, Newton’s physics breaks down and relativity takes over, causing the release of light in the form of attosecond pulses.

To improve the technique, Matthew Edwards, a graduate student in Mikhailova’s lab, ran simulations of plasma-laser interactions on Princeton’s TIGRESS high-performance computer cluster. The results, published Sept. 16, 2016, in the journal Physical Review Letters, showed that mixing laser light with light at harmonic frequencies — which are multiples of the original laser’s frequency — increases the efficiency of the process.

In a paper published Feb. 24, 2016, in the journal Physical Review A, the researchers proposed an extremely efficient two-target system: the first target generates light with harmonic frequencies, which hits the second target to generate attosecond pulses. With such powerful pulses, a new domain becomes visible, Mikhailova said. “We may be able to really see what the electron is doing as it ‘orbits’ in the atom.” –By Bennett McIntosh

Exploring the emergence of Cuban consumerism

DENNISSE CALLE FOUND THE TOPIC for her senior thesis along a Havana street in the back of a stall that sells pirated movies and music.

Cubans pay the equivalent of a few dollars, insert a flash drive into the computer at the back of the stall, and get access to El Paquete — a weekly, one-terabyte compilation of popular TV shows, movies, music, computer and phone apps, and advertisements that serves as an offline Netflix, YouTube, Craigslist and more in a country where internet access is slow and expensive.  Calle, a sociology major at Princeton, spent two weeks in January doing research in Cuba and interviewed 50 users and distributors of El Paquete — which means “The Package” — to learn about the service and the way it fits into the lives of everyday Cubans.

“I focus on how El Paquete is transforming how people view themselves as consumers,” Calle said. “This is one of the first forms of consumer culture that is being normalized in Cuba, in part because it’s cheap and easy to pass around.”

The origins of El Paquete, which began around 2008, are unclear, as is the identity of the people behind it. El Paquete is  widely available — either distributed door to door using a portable hard drive or from central locations like the stall where Calle discovered it — despite existing in a sort of legal gray area in Cuba.

It offers an alternative to state-controlled Cuban television, which broadcasts only 10 channels of news and sedate fare to most residents.

Many of the TV shows and movies — generally subtitled in Spanish — come from the United States, along with the United Kingdom and Spain. Competition shows such as “The Voice” and “Cake Wars” are popular, as are South Korean soap operas.  Calle, who is originally from Ecuador and moved to Trenton, New Jersey, also looked beyond the content to explore how El Paquete is changing the way people see themselves. “I think it’s reflective of what’s happening in Cuba, moving from a state that is very controlling to one that is allowing capitalism to emerge into the nation and its culture,” she said.

Calle’s research and analysis are impressive, said her adviser, Patricia Fernandez-Kelly, a senior lecturer in sociology. “It’s really a study about identity,” Fernandez-Kelly said. “Not just personal identity but national identity.”

What’s ahead for El Paquete in Cuba, which has been working to ease tensions with the United States? Calle predicts El Paquete will survive even if Cubans gain broader access to the internet —  in part because it is so inexpensive and easily shared.  –By Michael Hotchkiss

The literature of madness and how it shaped modern psychiatry

IN 1890, THE RUSSIAN PHYSICIAN and writer Anton Chekhov traveled across Siberia to document the lives of prisoners sentenced to a remote penal colony on Sakhalin Island. The visit inspired not only a nonfiction exposé but also several works of fiction, including a famous short story, “Ward Number Six,” about the ill-fated friendship of a doctor and a paranoiac patient in a rural Russian institution.

Science and medicine often provide the inspiration for literature, but graduate student Cate Reilly notes that the reverse also can be true. In an effort to establish psychiatry as a legitimate medical science, German physicians in the period from the 1890s to the late 1920s created a standardized terminology, one that eventually formed the basis of our present-day diagnostic manual of mental illness. Reilly, a doctoral student in comparative literature, is exploring how the literary descriptions of mental disorders by Russian and German-language fiction writers contributed to the science of mental illness in ways that stay with us today.

“The story that hasn’t been told is about the birth of these terms and how literature influenced the development of our current international classification system for mental disorders,” Reilly said. “This was all happening at a time of tremendous exchanges between psychiatrists in Germany and Russia. Those nations’ creative writers, some of whom were doctor-physicians like Chekhov, were involved in and contributed to this classification system.”

Reilly was inspired to explore this interdisciplinary area in part by modern debates over the extent to which definitions of pathologies are shaped by culture. At one time, mental illnesses included homosexuality and “indigenous psychopathology,” a diagnosis given by French physicians to native Algerians to justify their subjugation. “Once you have the standardization of these terms, then you start to see their abuse for purposes of power,” Reilly said.

Reilly explores how psychiatry and literature influenced each other during this critical time by citing works by Chekhov, Russian playwright Nikolai Evreinov, and German-language authors Rainer Maria Rilke and Alfred Döblin. For example, Evreinov’s dramas drew themes from German psychology and the anatomical-imaging technologies available during the 1880s and 1890s. Döblin’s 1924 “true-crime” novella, Two Girlfriends Commit Murder by Poisoning, about a court case involving lesbians who plotted to kill their husbands, featured pages of pseudoscientific diagrams to explain the women’s mental states.

“When creative writers influence what happens in psychiatry, it is not so much the case of a specific work of literature influencing a single term or definition, but the opening of a space for experimentation in how mental illness is characterized,” Reilly said. –By Catherine Zandonella

Cuban literature and culture are focus of Planet/Cuba

RACHEL PRICE, an associate professor of Spanish and Portuguese who also is affiliated with the Program in Media and Modernity, joined Princeton in 2009. Her scholarship focuses on culture, media, poetics, empire and ecocriticism in Latin American, Caribbean and, particularly, Cuban literature.  In her book Planet/Cuba (2015, Verso Books), Price addresses contemporary literature as well as conceptual, digital and visual art from Cuba that engages questions of environmental crisis, new media, and new forms of labor and leisure.

What inspired you to write this book?

I wanted to think about the many positions Cuba has occupied in its own imagination and for the rest of the world. Cuban history has always been inescapably global — it was shaped by empires, by massive slave trade, and by sitting at the junction of international trade routes. Both because of and despite this, Cuba is often discussed as singular: sometimes as a theme park, or as a world apart, as a kind of “Planet Cuba.” By introducing the slash [in the title], I also wanted to call attention to the indissociable relation between Cuba and the planet.

The book has a strong emphasis on ecology. How are artists addressing issues of climate change and issues such as the impact of deforestation in Cuba?

So much of life in Cuba, like anywhere on the planet, is deeply marked by an engagement with the environment. In cities, where food security is an issue; in the countryside, where drought is an increasing problem and where invasive species restore nitrates to land worn out by sugar but also thwart agriculture; and in the water, where fishing is diminished.

Artists and writers engage ecological questions both on the local and global scales. To give just a few examples, they may make humorous video art about the failures of agricultural reform in Cuba, create installations (“environments”) that involve living trees, or write speculative fiction — another term for science fiction — that imagines mass migrations caused by ever increasing hurricanes in the Caribbean.

How does art-making in Cuba reflect issues of surveillance and state security?

Artists use a variety of approaches: hacking into systems of transmission and rebroadcasting information; creating exhibits that force viewers to participate unwittingly in being surveilled; producing video-game art that simulates a famous Panopticon prison [such as Cuba’s Presidio Modelo]; and so on.

What interested me in particular was the way that art references the particularities of Cuba’s network of vigilance, but goes beyond it to comment on — or intervene into — the more pervasive global systems of surveillance, both state and corporate, in which we all participate. –By Jamie Saxon