Boojum (superfluidity)
Encyclopedia
In the physics
of superfluidity, a boojum is a geometric pattern on the surface of one of the phase
s of superfluid
helium-3
, whose motion can result in the decay of a supercurrent
. A boojum can result from a monopole singularity in the bulk of the liquid being drawn to, and then "pinned" on a surface. Although superfluid helium-3 only exists within a few thousandths of a degree of absolute zero
, boojums have also been observed forming in various liquid crystal
s at room temperature.
The boojum was named by David Mermin
of Cornell University
in 1976. He was inspired by Lewis Carroll
's poem The Hunting of the Snark
. As in the poem, the appearance of a boojum can cause something (in this case, the supercurrent) to "softly and suddenly vanish away". Other, less whimsical names had already been suggested for the phenomenon, but Mermin was persistent. After an exchange of letters that Mermin describes as both "lengthy and hilarious", the editors of Physical Review Letters
agreed to his terminology. Research using the term "boojum" in a superfluid context was first published in 1977, and the term has since gained widespread acceptance in broader areas of physics. Its Russian phonetic equivalent is "budzhum", which is also well accepted by physicists.
The plural of the term is "boojums", a word initially disliked by Mermin (who at first used "booja") but one which is defined unambiguously by Carroll in his poem.
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
of superfluidity, a boojum is a geometric pattern on the surface of one of the phase
Phase (matter)
In the physical sciences, a phase is a region of space , throughout which all physical properties of a material are essentially uniform. Examples of physical properties include density, index of refraction, and chemical composition...
s of superfluid
Superfluid
Superfluidity is a state of matter in which the matter behaves like a fluid without viscosity and with extremely high thermal conductivity. The substance, which appears to be a normal liquid, will flow without friction past any surface, which allows it to continue to circulate over obstructions and...
helium-3
Helium-3
Helium-3 is a light, non-radioactive isotope of helium with two protons and one neutron. It is rare on Earth, and is sought for use in nuclear fusion research...
, whose motion can result in the decay of a supercurrent
Supercurrent
A supercurrent is a superconducting current, that is, electric current which flows without dissipation....
. A boojum can result from a monopole singularity in the bulk of the liquid being drawn to, and then "pinned" on a surface. Although superfluid helium-3 only exists within a few thousandths of a degree of absolute zero
Absolute zero
Absolute zero is the theoretical temperature at which entropy reaches its minimum value. The laws of thermodynamics state that absolute zero cannot be reached using only thermodynamic means....
, boojums have also been observed forming in various liquid crystal
Liquid crystal
Liquid crystals are a state of matter that have properties between those of a conventional liquid and those of a solid crystal. For instance, an LC may flow like a liquid, but its molecules may be oriented in a crystal-like way. There are many different types of LC phases, which can be...
s at room temperature.
The boojum was named by David Mermin
David Mermin
Nathaniel David Mermin is a solid-state physicist at Cornell University best known for the eponymous Mermin-Wagner theorem and his application of the term "Boojum" to superfluidity, and for the quote "Shut up and calculate!"Together with Neil W...
of Cornell University
Cornell University
Cornell University is an Ivy League university located in Ithaca, New York, United States. It is a private land-grant university, receiving annual funding from the State of New York for certain educational missions...
in 1976. He was inspired by Lewis Carroll
Lewis Carroll
Charles Lutwidge Dodgson , better known by the pseudonym Lewis Carroll , was an English author, mathematician, logician, Anglican deacon and photographer. His most famous writings are Alice's Adventures in Wonderland and its sequel Through the Looking-Glass, as well as the poems "The Hunting of the...
's poem The Hunting of the Snark
The Hunting of the Snark
The Hunting of the Snark is usually thought of as a nonsense poem written by Lewis Carroll in 1874, when he was 42 years old...
. As in the poem, the appearance of a boojum can cause something (in this case, the supercurrent) to "softly and suddenly vanish away". Other, less whimsical names had already been suggested for the phenomenon, but Mermin was persistent. After an exchange of letters that Mermin describes as both "lengthy and hilarious", the editors of Physical Review Letters
Physical Review Letters
Physical Review Letters , established in 1958, is a peer reviewed, scientific journal that is published 52 times per year by the American Physical Society...
agreed to his terminology. Research using the term "boojum" in a superfluid context was first published in 1977, and the term has since gained widespread acceptance in broader areas of physics. Its Russian phonetic equivalent is "budzhum", which is also well accepted by physicists.
The plural of the term is "boojums", a word initially disliked by Mermin (who at first used "booja") but one which is defined unambiguously by Carroll in his poem.