23,545 research outputs found
Gauge invariant hydrogen atom Hamiltonian
For quantum mechanics of a charged particle in a classical external
electromagnetic field, there is an apparent puzzle that the matrix element of
the canonical momentum and Hamiltonian operators is gauge dependent. A
resolution to this puzzle is recently provided by us in [2]. Based on the
separation of the electromagnetic potential into pure gauge and gauge invariant
parts, we have proposed a new set of momentum and Hamiltonian operators which
satisfy both the requirement of gauge invariance and the relevant commutation
relations. In this paper we report a check for the case of the hydrogen atom
problem: Starting from the Hamiltonian of the coupled electron, proton and
electromagnetic field, under the infinite proton mass approximation, we derive
the gauge invariant hydrogen atom Hamiltonian and verify explicitly that this
Hamiltonian is different from the Dirac Hamiltonian, which is the time
translation generator of the system. The gauge invariant Hamiltonian is the
energy operator, whose eigenvalue is the energy of the hydrogen atom. It is
generally time-dependent. In this case, one can solve the energy eigenvalue
equation at any specific instant of time. It is shown that the energy
eigenvalues are gauge independent, and by suitably choosing the phase factor of
the time-dependent eigenfunction, one can ensure that the time-dependent
eigenfunction satisfies the Dirac equation.Comment: 7 pages, revtex4, some further discussion on Dirac Hamiltonian and
the gauge invariant Hamiltonian is added, one reference removed; new address
of some of the authors added, final version to appear in Phys. Rev.
Mapping epigenetic modifications by sequencing technologies
The “epigenetics” concept was first described in 1942. Thus far, chemical modifications on histones, DNA, and RNA have emerged as three important building blocks of epigenetic modifications. Many epigenetic modifications have been intensively studied and found to be involved in most essential biological processes as well as human diseases, including cancer. Precisely and quantitatively mapping over 100 [1], 17 [2], and 160 [3] different known types of epigenetic modifications in histone, DNA, and RNA is the key to understanding the role of epigenetic modifications in gene regulation in diverse biological processes. With the rapid development of sequencing technologies, scientists are able to detect specific epigenetic modifications with various quantitative, high-resolution, whole-genome/transcriptome approaches. Here, we summarize recent advances in epigenetic modification sequencing technologies, focusing on major histone, DNA, and RNA modifications in mammalian cells
Note On Certain Inequalities for Neuman Means
In this paper, we give the explicit formulas for the Neuman means ,
, and , and present the best possible upper and lower
bounds for theses means in terms of the combinations of harmonic mean ,
arithmetic mean and contraharmonic mean .Comment: 9 page
- …