604 research outputs found
Mass renormalization in nonrelativistic QED
In nonrelativistic QED the charge of an electron equals its bare value,
whereas the self-energy and the mass have to be renormalized. In our
contribution we study perturbative mass renormalization, including second order
in the fine structure constant , in the case of a single, spinless
electron. As well known, if denotes the bare mass and \mass the mass
computed from the theory, to order one has \frac{\mass}{m}
=1+\frac{8\alpha}{3\pi} \log(1+\half (\Lambda/m))+O(\alpha^2) which suggests
that \mass/m=(\Lambda/m)^{8\alpha/3\pi} for small . If correct, in
order the leading term should be \displaystyle \half
((8\alpha/3\pi)\log(\Lambda/m))^2. To check this point we expand \mass/m to
order . The result is as leading term, suggesting
a more complicated dependence of on
Ultraviolet Renormalization of the Nelson Hamiltonian through Functional Integration
Starting from the N-particle Nelson Hamiltonian defined by imposing an
ultraviolet cutoff, we perform ultraviolet renormalization by showing that in
the zero cutoff limit a self-adjoint operator exists after a logarithmically
divergent term is subtracted from the original Hamiltonian. We obtain this term
as the diagonal part of a pair interaction appearing in the density of a Gibbs
measure derived from the Feynman-Kac representation of the Hamiltonian. Also,
we show existence of a weak coupling limit of the renormalized Hamiltonian and
derive an effective Yukawa interaction potential between the particles.Comment: 28 pages, revision of section 2 and typos correcte
Kramers degeneracy theorem in nonrelativistic QED
Degeneracy of the eigenvalues of the Pauli-Fierz Hamiltonian with spin 1/2 is
proven by the Kramers degeneracy theorem. The Pauli-Fierz Hamiltonian at fixed
total momentum is also investigated.Comment: LaTex, 11 page
Letter from Members of the Hiroshima YMCA to Geraldine Ferraro
Letter from members of the Hiroshima YMCA to Geraldine Ferraro. The authors invite Ferraro to visit the Atomic Bomb Museum in Hiroshima. A letter from Laurence M. Wiig of the YMCA International Institute for Peace is enclosed.https://ir.lawnet.fordham.edu/vice_presidential_campaign_correspondence_1984_international/1360/thumbnail.jp
Scaling Limits for the System of Semi-Relativistic Particles Coupled to a Scalar Bose Field
In this paper the Hamiltonian for the system of semi-relativistic particles
interacting with a scalar bose field is investigated. A scaled total
Hamiltonian of the system is defined and its scaling limit is considered. Then
the semi-relativistic Schrodinger operator with an effective potential is
derived
Hyperfine splitting in non-relativistic QED: uniqueness of the dressed hydrogen atom ground state
We consider a free hydrogen atom composed of a spin-1/2 nucleus and a
spin-1/2 electron in the standard model of non-relativistic QED. We study the
Pauli-Fierz Hamiltonian associated with this system at a fixed total momentum.
For small enough values of the fine-structure constant, we prove that the
ground state is unique. This result reflects the hyperfine structure of the
hydrogen atom ground state.Comment: 22 pages, 3 figure
Quantum information with Gaussian states
Quantum optical Gaussian states are a type of important robust quantum states
which are manipulatable by the existing technologies. So far, most of the
important quantum information experiments are done with such states, including
bright Gaussian light and weak Gaussian light. Extending the existing results
of quantum information with discrete quantum states to the case of continuous
variable quantum states is an interesting theoretical job. The quantum Gaussian
states play a central role in such a case. We review the properties and
applications of Gaussian states in quantum information with emphasis on the
fundamental concepts, the calculation techniques and the effects of
imperfections of the real-life experimental setups.
Topics here include the elementary properties of Gaussian states and relevant
quantum information device, entanglement-based quantum tasks such as quantum
teleportation, quantum cryptography with weak and strong Gaussian states and
the quantum channel capacity, mathematical theory of quantum entanglement and
state estimation for Gaussian states.Comment: 170 pages. Minors of the published version are corrected and listed
in the Acknowledgement part of this versio
Ground State and Resonances in the Standard Model of Non-relativistic QED
We prove existence of a ground state and resonances in the standard model of
the non-relativistic quantum electro-dynamics (QED). To this end we introduce a
new canonical transformation of QED Hamiltonians and use the spectral
renormalization group technique with a new choice of Banach spaces.Comment: 50 pages change
Quantum teleportation scheme by selecting one of multiple output ports
The scheme of quantum teleportation, where Bob has multiple (N) output ports
and obtains the teleported state by simply selecting one of the N ports, is
thoroughly studied. We consider both deterministic version and probabilistic
version of the teleportation scheme aiming to teleport an unknown state of a
qubit. Moreover, we consider two cases for each version: (i) the state employed
for the teleportation is fixed to a maximally entangled state, and (ii) the
state is also optimized as well as Alice's measurement. We analytically
determine the optimal protocols for all the four cases, and show the
corresponding optimal fidelity or optimal success probability. All these
protocols can achieve the perfect teleportation in the asymptotic limit of
. The entanglement properties of the teleportation scheme are also
discussed.Comment: 14 pages, 4 figure
Field evolution of the magnetic structures in ErTiO through the critical point
We have measured neutron diffraction patterns in a single crystal sample of
the pyrochlore compound ErTiO in the antiferromagnetic phase
(T=0.3\,K), as a function of the magnetic field, up to 6\,T, applied along the
[110] direction. We determine all the characteristics of the magnetic structure
throughout the quantum critical point at =2\,T. As a main result, all Er
moments align along the field at and their values reach a minimum. Using
a four-sublattice self-consistent calculation, we show that the evolution of
the magnetic structure and the value of the critical field are rather well
reproduced using the same anisotropic exchange tensor as that accounting for
the local paramagnetic susceptibility. In contrast, an isotropic exchange
tensor does not match the moment variations through the critical point. The
model also accounts semi-quantitatively for other experimental data previously
measured, such as the field dependence of the heat capacity, energy of the
dispersionless inelastic modes and transition temperature.Comment: 7 pages; 8 figure
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