# Category Archives: Theoretical physics

## How to extract the interacting spectral function from a ground state DFT calculation

The electronic wave function of an n-electron molecule depends on 3n spatial and n spin coordinates. In a sense, the wave function of a many-electron molecule contains more information than is needed and is lacking in direct physical significance. This […]

## Higher-order topological insulators

Topological insulators are materials with special universal properties, which are protected against perturbations. Such properties are theoretically described by topology, a branch of mathematics concerned with the properties of geometrical objects that are unchanged by continuous deformations. Concretely, topological insulators […]

## The size of atoms, uncertainty and relativity

You may have read somewhere that atoms are actually made up mostly of empty space. The usual description goes more or less as follows. At the centre of each atom there is a very tiny nucleus, which carries all of […]

## Family unification (2): The SO(18) spinor strikes back

In the previous post, Family unification 1, we reviewed the historical development of Grand Unified Theories (GUT) of force and matter, i.e. Comprehensive Unification. We saw how the SO(18) spinor, 256, is able to accomodate the Standard Model […]

## Family unification (1)

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 […]

## How dopants induce plasmon decay in graphene

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 […]

## 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 […]