PVLAS
Encyclopedia
PVLAS is an apparatus
dedicated to the detection of dark matter
. It is located at the Legnaro National Laboratory of National Institute of Nuclear Physics
near Padova, Italy
. Experiments with the apparatus began in 2001.
As dark matter is a form of matter that does not emit
or reflect
enough electromagnetic radiation
to be detected directly, the PVLAS is used to detect the small flattening
acquired by a linearly polarised
laser beam after it passes through a vacuum
space where an intense magnetic field
has been applied.
More precisely in the presence of a massive dark matter candidate that interacts with the photon
, like the axion
, the virtual dark matter particles will be preferentially created by photons whose polarization is parallel to the external field. These virtual particles travel slower than the speed of light, and so the effective speed of the photons with a parallel polarization
is reduced. Thus the vacuum is birefringent
, as the index of refraction depends on the polarization. This flattening is characteristic of the propagation of light in a birefringent medium. Notice however that uncharged dark matter candidates will not interact with the photon and so will not be detectable by PVLAS. The birefrigence of the vacuum of quantum electrodynamics
in the presence of an external field is generally credited to Stephen L. Adler
, who presented the first general derivation in Photon splitting and photon dispersion in a strong magnetic field in 1971.
The PVLAS experiment investigates the vacuum after being perturbed by external magnetic fields.
Apparatus
Apparatus may refer to:*Technical term for body of the Soviet and post-Soviet governments *Machine*Equipment*Critical apparatus, the critical and primary source material that accompanies an edition of a text-See also:*Fire apparatus...
dedicated to the detection of dark matter
Dark matter
In astronomy and cosmology, dark matter is matter that neither emits nor scatters light or other electromagnetic radiation, and so cannot be directly detected via optical or radio astronomy...
. It is located at the Legnaro National Laboratory of National Institute of Nuclear Physics
Istituto Nazionale di Fisica Nucleare
The Istituto Nazionale di Fisica Nucleare is the coordinating institution for nuclear, particle and astroparticle physics in Italy. It was founded on the 8th of August 1951, to further the nuclear physics research tradition initiated by Enrico Fermi in Rome, in the 1930s...
near Padova, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
. Experiments with the apparatus began in 2001.
As dark matter is a form of matter that does not emit
Emission spectrum
The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted by the element's atoms or the compound's molecules when they are returned to a lower energy state....
or reflect
Reflection (physics)
Reflection is the change in direction of a wavefront at an interface between two differentmedia so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves...
enough electromagnetic radiation
Electromagnetic radiation
Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...
to be detected directly, the PVLAS is used to detect the small flattening
Flattening
The flattening, ellipticity, or oblateness of an oblate spheroid is a measure of the "squashing" of the spheroid's pole, towards its equator...
acquired by a linearly polarised
Linear polarization
In electrodynamics, linear polarization or plane polarization of electromagnetic radiation is a confinement of the electric field vector or magnetic field vector to a given plane along the direction of propagation...
laser beam after it passes through a vacuum
Vacuum
In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...
space where an intense magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
has been applied.
More precisely in the presence of a massive dark matter candidate that interacts with the photon
Photon
In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
, like the axion
Axion
The axion is a hypothetical elementary particle postulated by the Peccei-Quinn theory in 1977 to resolve the strong CP problem in quantum chromodynamics...
, the virtual dark matter particles will be preferentially created by photons whose polarization is parallel to the external field. These virtual particles travel slower than the speed of light, and so the effective speed of the photons with a parallel polarization
Photon polarization
Photon polarization is the quantum mechanical description of the classical polarized sinusoidal plane electromagnetic wave. Individual photons are completely polarized...
is reduced. Thus the vacuum is birefringent
Birefringence
Birefringence, or double refraction, is the decomposition of a ray of light into two rays when it passes through certain anisotropic materials, such as crystals of calcite or boron nitride. The effect was first described by the Danish scientist Rasmus Bartholin in 1669, who saw it in calcite...
, as the index of refraction depends on the polarization. This flattening is characteristic of the propagation of light in a birefringent medium. Notice however that uncharged dark matter candidates will not interact with the photon and so will not be detectable by PVLAS. The birefrigence of the vacuum of quantum electrodynamics
Quantum electrodynamics
Quantum electrodynamics is the relativistic quantum field theory of electrodynamics. In essence, it describes how light and matter interact and is the first theory where full agreement between quantum mechanics and special relativity is achieved...
in the presence of an external field is generally credited to Stephen L. Adler
Stephen L. Adler
Stephen Louis Adler is an American physicist specializing in elementary particles and field theory.-Biography:Adler was born in New York City. He received an A.B. degree at Harvard University in 1961, where he was a Putnam Fellow, and a Ph.D. from Princeton University in 1964...
, who presented the first general derivation in Photon splitting and photon dispersion in a strong magnetic field in 1971.
The PVLAS experiment investigates the vacuum after being perturbed by external magnetic fields.
External links
- Exploring the Quantum Vacuum and its structure - Istituto Nazionale di Fisica Nucleare (INFN)
- Axion Interpretation of PVLAS Data? - 9th International Conference on Topics in Astroparticle and Underground Physics (TAUP 2005) September 10 - 14, 2005, University of Zaragoza, Zaragoza, Spain