Skip to main content
  • Home
  • About
  • Faculty Experts
  • For The Media
  • Videos
  • Topics
    • Alumni
    • Events
    • Faculty
    • Library
    • Research
    • Students
    • All Topics
  • Contact
  • Submit
STEM
  • All News
  • Arts & Culture
  • Business & Economy
  • Campus & Community
  • Health & Society
  • Media, Law & Policy
  • STEM
  • Veterans
  • |
  • Alumni
  • The Peel
  • Athletics
Sections
  • All News
  • Arts & Culture
  • Business & Economy
  • Campus & Community
  • Health & Society
  • Media, Law & Policy
  • STEM
  • Veterans
  • |
  • Alumni
  • The Peel
  • Athletics
  • Home
  • About
  • Faculty Experts
  • For The Media
  • Videos
  • Topics
    • Alumni
    • Events
    • Faculty
    • Library
    • Research
    • Students
    • All Topics
  • Contact
  • Submit
STEM

Curious Properties

Monday, September 11, 2017, By News Staff
Share
College of Arts and SciencesfacultyresearchSTEM

Editor’s Note: The following piece was prepared for the Kavli Institute for Theoretical Physics (KITP) at the University of California, Santa Barbara. The article highlights three members of Syracuse’s Department of Physics: Mark Bowick, the Joel Dorman Steele Professor of Physics, as well as a visiting scientist and deputy director at KITP; Cristina Marchetti, the William R. Kenan Distinguished Professor of Physics and a KITP general member; and Suraj Shankar, a Ph.D. student and KITP Graduate Fellow. 

A murmuration of starlings. The phrase reads like something from literature or the title of an arthouse film. In fact, it is meant to describe the phenomenon that results when hundreds, sometimes thousands, of these birds fly in swooping, intricately coordinated patterns through the sky.

Or in more technical terms, flocking.

Mark Bowick

Mark Bowick (Photo by Sonia Fernandez)

But birds are not the only creatures that flock. Such behavior also takes place on a microscopic scale, such as when bacteria roam the folds of the gut. Yet bird or bacteria, all flocking has one prerequisite: The form of the entity must be elongated with a “head” and “tail” to align and move with neighbors in an ordered state.

Physicists study flocking to better understand dynamic organization at various scales, often as a way to expand their knowledge of the rapidly developing field of active matter. Case in point is a new analysis by a group of theoretical physicists, including Mark Bowick, deputy director of UC Santa Barbara’s Kavli Institute for Theoretical Physics (KITP).

Generalizing the standard model of flocking motion to the curved surface of a sphere rather than the usual linear plane or flat three-dimensional space, Bowick’s team found that instead of spreading out uniformly over the whole sphere, arrowlike agents spontaneously order into circular bands centered on the equator. The team’s findings appear in the journal Physical Review X.

“Whether it’s bacteria swarming, cells roaming or energy-consuming ‘arrows’ flying, these systems share universal characteristics independent of the precise size and structure of the agents as well as their detailed interactions,” said corresponding author Bowick, who is on leave from Syracuse University while in his role at KITP. “The ordered states of these systems are never perfectly uniform, so fluctuations in density generate sound, much in the same way that wind instruments create music.”

On curved surfaces, the team, which includes KITP general member [and Syracuse’s Kenan Distinguished Professor of Physics] Cristina Marchetti and KITP graduate fellow Suraj Shankar, found “special” sound modes that don’t dissipate and flow around obstacles. According to Bowick, these special modes correspond to special harmonics or tones that don’t mix with all the other harmonics.

He also noted that these modes are special precisely because the band geometry of the equator is very different from the planar geometry of a flat surface. For example, a particle moving on a ring comes back to its starting point even though it moves along a “straight” path. This doesn’t happen on a plane, where entities continue forever in a straight line, never to return, unless they encounter an edge. This feature is a direct consequence of the very different topology of the sphere and the plane.

sphere and catenoid

Steady flocks on a sphere and a catenoid. (Courtesy of Suraj Shankar)

“Even though a sphere itself has no edge, the swarming patterns have an edge—the edge of the band,” Bowick said. “So simply by locally consuming energy, active agents on the sphere spontaneously swarm and create an edge.”

The authors also analyzed another curved shape, an hourglass-shaped figure called a catenoid. Unlike a sphere on which parallel lines converge, the catenoid’s concave curvature causes parallels to diverge. This opposite curvature pushes the flocking entities and associated sound waves to the top and bottom edges of the hourglass, leaving the middle bare—the opposite of what happens on a sphere.

“Just the fact that these systems flock is pretty remarkable because they dynamically generate motion,” said Shankar, a doctoral student in the soft matter program in Syracuse University’s physics department. “But they are far richer systems than we expected because they also generate these ‘topologically protected’ sound modes.”

  • Author

News Staff

  • Recent
  • IVMF Advisory Board Welcomes New Additions
    Monday, January 18, 2021, By News Staff
  • Syracuse Stage Announces Changes to the 2020/2021 Season
    Sunday, January 17, 2021, By Joanna Penalva
  • Hehnly Lab Awarded $1.2M NIH Grant to Research Critical Tissue Formation
    Sunday, January 17, 2021, By Dan Bernardi
  • Important Information Regarding Proof of Eligibility for and Access to the COVID Vaccine
    Saturday, January 16, 2021, By News Staff
  • COVID-19 Update: Vaccination | Testing | Important Reminders | Zoom Sessions
    Friday, January 15, 2021, By News Staff

More In STEM

Hehnly Lab Awarded $1.2M NIH Grant to Research Critical Tissue Formation

A key process during the development of an embryo is tissue morphogenesis, where the number of cells in an organism increase through cell division and tissues begins to take shape. Heidi Hehnly, assistant professor of biology, has been awarded a…

The Role of Digital Forensics and Tracking Down US Capitol Riot Criminals

With just under a week left before President-elect Joe Biden’s inauguration ceremony, investigators and law enforcement agencies across the country are working speedily to identify as many of the Jan. 6 U.S. Capitol riot offenders as they can. Knowing exactly…

A&S Researchers Awarded $2.1M Grant to Study Causes of Congenital Heart Defects

Congenital heart defects are the most common type of birth defect, affecting nearly 1 percent of births in the United States each year, according to the Centers for Disease Control and Prevention. Doctors have been unable to lower that number…

$1.5 Million NIH Grant Funds ALS-Linked Research

The human body is made up of trillions of cells. Within each cell are proteins which help to maintain the structure, function and regulation of the body’s tissues and organs. When cells are under stress, as in response to heat…

Professor Shikha Nangia Selected as Associate Editor for ACS Applied Bio Materials Journal

Biomedical and chemical engineering Professor Shikha Nangia was selected as the associate editor for the ACS Applied Bio Materials journal. ACS Applied Bio Materials is an interdisciplinary journal publishing original research covering all aspects of biomaterials and biointerfaces including and beyond…

Subscribe to SU Today

If you need help with your subscription, contact sunews@syr.edu.

Connect With Us

  • Twitter
  • Facebook
  • Instagram
  • Youtube
  • LinkedIn
Social Media Directory

For the Media

Find an Expert Follow @SyracuseUNews
  • Facebook
  • Instagram
  • Youtube
  • LinkedIn
  • @SyracuseU
  • @SyracuseUNews
  • @SUCampus
  • Social Media Directory
  • Accessibility
  • Privacy
  • Campus Status
  • Syracuse.edu
© 2021 Syracuse University News. All Rights Reserved.