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Related Concept Videos

Atomic Nuclei: Nuclear Magnetic Moment00:59

Atomic Nuclei: Nuclear Magnetic Moment

All atomic nuclei are positively charged. When they have a nonzero spin, they behave like rotating charges. As a consequence of their charge and spin, these nuclei generate a magnetic field (B). This, in turn, gives rise to a magnetic moment (μ), which is randomly oriented in the absence of an external magnetic field. When an external magnetic field (B0) is applied, the magnetic moment vectors can align with the field or against it in 2 + 1 orientations. A hydrogen nucleus, which is just a...
Magnetic Fields01:27

Magnetic Fields

A moving charge or a current creates a magnetic field in the surrounding space, in addition to its electric field. The magnetic field exerts a force on any other moving charge or current that is present in the field. Like an electric field, the magnetic field is also a vector field. At any position, the direction of the magnetic field is defined as the direction in which the north pole of a compass needle points.
A magnetic field is defined by the force that a charged particle experiences...
Atomic Nuclei: Nuclear Relaxation Processes01:23

Atomic Nuclei: Nuclear Relaxation Processes

In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis,  the precessing magnetic moments are randomly oriented around the z-axis. This...
Atomic Nuclei: Larmor Precession Frequency01:11

Atomic Nuclei: Larmor Precession Frequency

The earth's gravitational field produces a 'twisting force' perpendicular to the angular momentum of a spinning mass (such as a spinning top) that causes the mass to 'wobble' around the gravitational field axis in a phenomenon called precession. Similarly, the magnetic moment (μ) of a spinning nucleus precesses due to an external magnetic field directed along the z-axis. The precession of the magnetic moment vector about the magnetic field is called Larmor precession, and the angular frequency...
Motion Of A Charged Particle In A Magnetic Field01:22

Motion Of A Charged Particle In A Magnetic Field

A charged particle experiences a force when moving through a magnetic field. Consider the field to be uniform and the charged particle to move perpendicular to it. If the field is in a vacuum, the magnetic field is the dominant factor determining the motion. Since the magnetic force is perpendicular to the direction of motion, a charged particle follows a curved path. The particle continues to follow this curved path until it forms a complete circle. Another way to look at this is that the...
Diamagnetic Shielding of Nuclei: Local Diamagnetic Current01:14

Diamagnetic Shielding of Nuclei: Local Diamagnetic Current

An applied magnetic field causes the electrons present in the molecule to circulate, setting up a local diamagnetic current within the molecule. The local diamagnetic current arising from circulating sigma-bonding electrons induces a magnetic field, Blocal that opposes the applied magnetic field, B0. The effective magnetic field experienced by these nuclei is given by the difference between the applied and local magnetic fields in a phenomenon called local diamagnetic shielding. Essentially,...

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Related Experiment Video

Updated: Jun 28, 2026

Setting Limits on Supersymmetry Using Simplified Models
07:46

Setting Limits on Supersymmetry Using Simplified Models

Published on: November 15, 2013

Helical magnetic fields from sphaleron decay and baryogenesis.

Craig J Copi1, Francesc Ferrer, Tanmay Vachaspati

  • 1CERCA, Department of Physics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-7079, USA.

Physical Review Letters
|November 13, 2008
PubMed
Summary

Baryogenesis models generate helical cosmic magnetic fields through electroweak dynamics. These fields, though weaker than predicted, offer a new way to study particle physics and CP violation.

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Optimized Setup and Protocol for Magnetic Domain Imaging with In Situ Hysteresis Measurement
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Optimized Setup and Protocol for Magnetic Domain Imaging with In Situ Hysteresis Measurement

Published on: November 7, 2017

Related Experiment Videos

Last Updated: Jun 28, 2026

Setting Limits on Supersymmetry Using Simplified Models
07:46

Setting Limits on Supersymmetry Using Simplified Models

Published on: November 15, 2013

Optimized Setup and Protocol for Magnetic Domain Imaging with In Situ Hysteresis Measurement
09:43

Optimized Setup and Protocol for Magnetic Domain Imaging with In Situ Hysteresis Measurement

Published on: November 7, 2017

Area of Science:

  • Cosmology
  • Particle Physics
  • Astrophysics

Background:

  • Baryogenesis models often invoke anomalous particle physics for baryon number violation.
  • Understanding the origin of cosmic magnetic fields is a key challenge in astrophysics.

Purpose of the Study:

  • To investigate the generation of helical cosmic magnetic fields by baryogenesis.
  • To compare numerical results with analytical estimates of magnetic field helicity.

Main Methods:

  • Numerical evolution of electroweak equations on a lattice.
  • Analysis of Chern-Simons number and electromagnetic helicity conservation.

Main Results:

  • Baryogenesis in these models creates helical cosmic magnetic fields.
  • The generated helicity is smaller than predicted by earlier analytical estimates.
  • Electroweak dynamics conserve Chern-Simons number and total electromagnetic helicity after a transitory period.

Conclusions:

  • Baryogenesis can produce astrophysically relevant magnetic fields of nano-Gauss strength.
  • Helical magnetic fields serve as an independent probe for baryogenesis and CP violation.