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Sequestration is a proposed way to confine certain particles and forces to extra dimensions, solving problems in particle physics. It is relevant to string theory, M theory, and supersymmetry. Sequestration can solve the hierarchy problem while avoiding flavor violation. Supersymmetry theory provides one possible explanation, but there is a problem with supersymmetry. Sequestration can prevent flavor violations by sequestering supersymmetry breaking in a separate brane. The theory can be tested by the Large Hadron Collider, but as of 2011, experiments have failed to detect superpartners. The idea may still have useful applications in physics.
In the context of physics, sequestration is a proposed means by which certain particles and forces can be confined to extra dimensions, by preventing or minimizing their interaction with the particles and forces that make up the Standard Model. The idea, which has particular relevance to string theory, M theory and supersymmetry (SUSY), was developed by theoretical physicists Lisa Randall and Raman Sundrum. The seizure can solve some important problems in particle physics. In particular, it offers a solution to what is known as the “hierarchy problem” through supersymmetry breaking, while avoiding another problem known as “flavor violation”.
Physicists have long sought a Grand Unified Theory (GUT) that unifies the four forces of nature – the electromagnetic force, the strong and weak nuclear forces, and gravity – as well as explaining the properties of all elementary particles. The big problem facing any such theory is the apparent incompatibility of general relativity with quantum theory and the Standard Model. String theory, in which the fundamental units of matter, such as electrons and quarks, are considered to be extremely small, one-dimensional, string-like entities, is an attempt at such a theory. This was developed in M-theory, where strings can be extended into two- and three-dimensional “branes” floating in a higher dimensional space, known as the “bulk.”
In addition to the problems involved in bringing gravity into the picture, there is a problem with the standard model itself, known as the hierarchy problem. To put it simply, the hierarchy problem centers on why the gravitational force is vastly weaker than the other forces of nature, but it also involves predicted values for the masses of some hypothetical force-carrying particles that differ vastly from each other. other. One hypothetical particle in particular, the Higgs particle, is expected to be relatively light, while it appears that the quantum contributions of virtual particles must make it vastly more massive, at least without an extraordinary degree of fine-tuning. This is considered extremely unlikely by most physicists, so some underlying principle is sought to explain the disparities.
Supersymmetry theory (SUSY) provides one possible explanation. This states that for every fermion – or matter-forming particle – there is a boson – or force-carrying particle – and vice versa, so that every particle in the Standard Model has a supersymmetric partner or “superpartner”. Since these superpartners have not been observed, it means that the symmetry is broken and that supersymmetry exists only at very high energies. According to this theory, the hierarchy problem is solved by the fact that the mass contributions of the virtual particles and their superpartners cancel out, removing the apparent discrepancies in the Standard Model. There is, however, a problem with supersymmetry.
The particles that make up fundamental matter such as quarks come in three generations or “flavors,” with different masses. When supersymmetry is broken, it appears that all sorts of interactions could occur, some of which would change the flavors of these particles. Since these interactions are not observed experimentally, any theory of supersymmetry breaking must somehow include a mechanism that prevents so-called flavor violations.
This is where seizure comes into play. Returning to the concept of three-dimensional branes floating in a higher dimensional mass, it is possible to sequester the supersymmetry breaking in a brane separate from the one on which the Standard Model particles and forces reside. Supersymmetry breaking effects could be communicated to the Standard Model brane by force-carrying particles that are able to move within the mass, but otherwise, the Standard Model particles will behave in the same way as unbroken supersymmetry. The particles in the mass that could interact with both the symmetry-breaking brane and the Standard Model brane would determine which interactions can occur, and could rule out flavor-changing interactions that we don’t observe. The theory works well if the graviton, the hypothetical gravity-bearing particle, plays this role.
Unlike many other ideas related to string theory and M-theory, it seems possible to test sequestered supersymmetry. It makes predictions for the masses of superpartner bosons – force-carrying particles – that fall within the range of energies achievable at the Large Hadron Collider (LHC). If these particles are observed by the LHC, their masses can be matched to what is expected. As of 2011, however, experiments at the LHC have failed to detect these superpartners at the energies they should have appeared at, a result that appears to rule out the simplest version of SUSY, though not some more complex versions. Even if SUSY is proven wrong, the kidnapping idea may still have useful applications regarding other problems and mysteries of physics.
