# Category Archives: Theoretical physics

## Metric structures in General Relativity

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 […]

## The tautomerization of porphycene on Cu(111) in simple physical terms

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 […]

## A link between straintronics and valleytronics in graphene

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 […]

## How to study magnetic Weyl fermions experimentally

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 […]

## On the spin geometry of String Theory

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 […]

## The geometry of String Compactifications (III): exploring the Calabi-Yau manifold

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 […]

## The geometry of String Theory compactifications (II): finding the Calabi-Yau manifold

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 […]

## The geometry of String Theory compactifications (I): the basics.

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 […]

## How to measure tiny temperature differences using a Josephson junction

At low temperatures, the resistivity of a metal (the inverse of its conductivity) is nearly constant. As the temperature of a material is lowered and as we approach absolute zero the resistivity should approach a constant value. Many metals, […]

## Unveiling the origin of the record superconductivity

Achieving room temperature superconductivity is among the most pursued but elusive goals of scientists. A paper uploaded to the arXiv in December 2014 claims to have observed superconductivity as high as 190 K in hydrogen sulfide at high […]