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  2. Dirac cone - Wikipedia

    en.wikipedia.org/wiki/Dirac_cone

    In k-space, this shows up as a hypercone, which have doubly degenerate bands which also meet at Dirac points. [11] Dirac semimetals contain both time reversal and spatial inversion symmetry; when one of these is broken, the Dirac points are split into two constituent Weyl points, and the material becomes a Weyl semimetal.

  3. Graphene - Wikipedia

    en.wikipedia.org/wiki/Graphene

    Graphene is a zero-gap semiconductor because its conduction and valence bands meet at the Dirac points. The Dirac points are six locations in momentum space on the edge of the Brillouin zone, divided into two non-equivalent sets of three points. These sets are labeled K and K'.

  4. Electronic properties of graphene - Wikipedia

    en.wikipedia.org/wiki/Electronic_properties_of...

    The two bands touch at the zone corners (the K point in the Brillouin zone), where there is a zero density of states but no band gap. The graphene sheet thus displays a semimetallic (or zero-gap semiconductor) character. Two of the six Dirac points are independent, while the rest are equivalent by symmetry.

  5. Dirac matter - Wikipedia

    en.wikipedia.org/wiki/Dirac_matter

    The Dirac velocity gives the gradient of the dispersion at large momenta , is the mass of particle or object. In the case of massless Dirac matter, such as the fermionic quasiparticles in graphene or Weyl semimetals, the energy-momentum relation is linear,

  6. Light-cone coordinates - Wikipedia

    en.wikipedia.org/wiki/Light-cone_coordinates

    The spatial coordinate of a point on the string is conveniently described by a parameter which runs from to . Time is appropriately described by a parameter σ 0 {\displaystyle \sigma _{0}} . Associating each point on the string in a D-dimensional spacetime with coordinates x 0 , x {\displaystyle x_{0},x} and transverse coordinates x i , i = 2

  7. Dirac delta function - Wikipedia

    en.wikipedia.org/wiki/Dirac_delta_function

    A so-called uniform "pulse train" of Dirac delta measures, which is known as a Dirac comb, or as the Sha distribution, creates a sampling function, often used in digital signal processing (DSP) and discrete time signal analysis. The Dirac comb is given as the infinite sum, whose limit is understood in the distribution sense,

  8. Dirac structure - Wikipedia

    en.wikipedia.org/wiki/Dirac_structure

    In mathematics a Dirac structure is a geometric structure generalizing both symplectic structures and Poisson structures, and having several applications to mechanics. It is based on the notion of the Dirac bracket constraint introduced by Paul Dirac and was first introduced by Ted Courant and Alan Weinstein .

  9. Interaction picture - Wikipedia

    en.wikipedia.org/wiki/Interaction_picture

    Where the Hamiltonian in this case is the QED interaction Hamiltonian, but it can also be a generic interaction, and is a spacelike surface that is passing through the point . The derivative formally represents a variation over that surface given fixed. It is difficult to give a precise mathematical formal interpretation of this equation.