Category archives: Theoretical physics

Our core theory of fundamental physics, the Standard Model (SM), describes a vast range of phenomena precisely and very accurately. In that sense it is close to Nature’s last word. It presents, however, some shortcomings. For example, the SM contains three different forces and many independent fields. It is attractive to imagine that a deeper […]

For centuries, metals were employed in optical applications only as mirrors and gratings. New vistas opened up in the late 1970s and early 1980s with the discovery of surface-enhanced Raman scattering and the use of surface plasmon (collective electronic oscillations at the surface of metals) resonances for sensing. However, it was not until the 1990s […]

Reference contains the following statement: “Ashtekar’s formulation of general relativity taught us to think of gravitational theories as theories of connections, on a bare manifold with no metric structure. […] The idea that general relativity has its deepest formulation as a connection theory suggested immediately a new approach to the unification of general relativity with […]

There are compounds, called isomers, that have the same molecular formulae but different molecular structures or different arrangements of atoms in space. In the so-called cis-trans isomerism, isomers have different positions of groups or specific atoms with respect to a double bond, a ring or a central atom. For example, the numbers in the name […]

So-called “valleytronics” is a new type of electronics that could lead to faster and more efficient computer logic systems and data storage chips in next-generation devices. Valley electrons are so named because they carry a valley “degree of freedom.” This is a new way to harness electrons for information processing that’s in addition to utilizing […]

Imagine there exist a material in which an electron could be split into two quasiparticles. These two quasiparticles both would carry electric charge, move in opposite directions but could not move backwards. Furthermore these quasiparticles would be massless. And we can give them a fancy name, Weyl fermions. This seems to be at odds with […]

The purpose of this note is to introduce the reader to the notion of Lipschitz structure and its potential applications to the spin geometry required to globally formulate string theory and supergravity on a differentiable manifold. Spinors are a crucial ingredient in the global formulation of string/M-Theory and its low energy limit supergravity, since these […]

In the previous articles (I, II), we have characterized the simplest class of supersymmetric heterotic compactification backgrounds. In particular, we have finished the second article with the following result: There is a class of admissible Heterotic internal manifolds characterized as being six-dimensional, oriented, spin, Riemannian compact manifolds admitting a parallel spinor respect to the Levi-Civita […]

This is the second of the series of articles on the geometry of String Theory compactifications. Before reading this note, the interested reader may want to read the first note, where the concept of compactification background is introduced in the context of String Theory and M-Theory compactifications. As it is well known, to be well-defined […]

This is first of a series of notes on the geometry of String Theory compactifications. The space-time in String Theory is often described by means of a mathematical object called manifold . Manifolds are very important objects from the mathematical and the physics point of view, not only in String Theory. For example, differential geometry […]