Particle Physics Essay Example | Topics and Well Written Essays - 7000 words

Particle Physics - Essay Example Search for a complete or full particle physics model is still on and experts are exploring the options of either producing a completely new innovative theory or model or constructing an efficient model merging the relative gravity and the Standard Models. This search saw the emergence of a variety of new-age models beyond the Standard Model. However, merging these theories is not so simple as it sounds and there are some difficulties that need to be tackled (Green et. al., 1987). These models are build upon different basic assumptions and concepts and this is why one finds it difficult to merge such models. QFT depends on particle fields embedded in the flat space-time of special relativity whereas, General Relativity accounts gravity as a curvature within space-time that changes as mass moves (Zee A., 2003). The simple option of merging these two theories considering gravity as another particle field seems to end up creating the so-called renormalization problem. As per the traditional understanding, gravity particles would attract each other and add up all the interactions resulting in many infinite values which cannot be easily cancelled out by methematical interventions (Linde, 1990), thereby ruling out the possibility of getting any sensible or finite results or values. This outcome is in contrast with quantum electrodynamics where, the addition of the interactions results in comparatively lesser infinite values which can be removed or cancelled out via renormalization (Banks, 1985). The long-range forces like the electromagnetic and gravity forces are believed to be meditated by massless particles with spin j 1 and as such, proper description of such massless particles in quantum field theory (QFT) is very important (Aitchison & Hey, 1989). This directionally brings in the fascinating approach of emergent gravity indicating that gravity may not be a component of fundamental physics. However, this concept of emergent gravity theory has been branded to be a misguided one by Steven Weinberg and Edward Witten (See, Jackson & Okun, 2001). Gravity was speculated to be an emergent phenemonon during the 1980s and supporting this, many theories like the 'Preon theories', Technicolor theories', etc. went on to regard that gluons might be composite. Noticing this, Weinberg & Witten came out with a 'no-go theorem' called the 'Weinberg-Witten Theorem' that excludes the hypothetical composite and emergent theories (Wienberg & Witten, HUTP-80). This theorem indicates that an i nteracting graviton cannot emerge from an ordinary Quantum Field Theory (QFT) in the same space-time. The Weinberg-Witten theorem forbids the existence of any massless particles with helicity j>1 in any theory with a Lorentz covariant energy-momentum tensor and also restricts charged massless particles of helicity>1/2 in any theory with a Lorentz covariant conserved current. This basically prohibits the existence of both graviton and the gluon but this can be avoided due to gauge symmetries. Taking on from here, this paper proceeds to decode and