25,603 research outputs found
Generalized dual symmetry of nonabelian theories, monopoles and dyons
In the present talk we present an investigation of nonabelian SU(N) gauge
theories, describing a system of fields with non--dual g and dual \tilde g
charges and revealing the generalized dual symmetry. The Zwanziger type action
is suggested. The renormalization group equations for pure nonabelian theories,
in particular for pure SU(3)\times\widetilde{SU(3)} gauge theory (as an
example) are analysed. We consider not only monopoles, but also dyons. The
behaviour of the QCD total beta--function is investigated. It was shown that
this beta--function is antisymmetric under the interchange
\alpha\leftrightarrow\frac 1\alpha (here \alpha\equiv\alpha_s), and has zero
("fixed point") at \alpha = 1. Monopoles, or dyons, are responsible for the
phase transition. Considering critical points at \alpha_1\approx 0.4 and
\alpha_2\approx 2.5, we give an explanation of the freezing of \alpha_s.Comment: 15 pages, 5 figures, Presented at the 12th Lomonosov Conference on
Elementary Particle Physics, Moscow State University, Moscow, 25-31 August,
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Comparative analysis of 18S rRNA genes from Myxobolus aeglefini Auerbach, 1906 isolated from cod (Gadus morhua), Plaice (Pleuronectes platessa) and dab (Limanda limanda), using PCR-RFLP
The myxosporean parasite Myxobolus aeglefini is a marine species, which can be found in the cartilage of mainly gadid fish species. The parasite has, however, been recorded in the flatfish plaice (Pleuronectes platessa) and dab (Limanda limanda). It is not clear if isolates from unrelated hosts represent the same species. Therefore a molecular study was conducted to reveal differences at the DNA level between these isolates. PCR was successfully conducted on three different isolates of Myxobolus aeglefini sampled from cod (Gadus morhua), plaice and dab respectively, using 18S rDNA as template. A PCR product of approx. 1600 base pairs was obtained and RFLP (Restriction Fragment Length Polymerase) was conducted on the fragment with the restriction enzymes Hinf I, Msp I and Hae III. No differences between the isolates were found, suggesting that the three isolates represent the same species
The Fundamental-Weak Scale Hierarchy in the Standard Model
The multiple point principle, according to which several vacuum states with
the same energy density exist, is put forward as a fine-tuning mechanism
predicting the ratio between the fundamental and electroweak scales in the
Standard Model (SM). It is shown that this ratio is exponentially huge: . Using renormalisation group equations for the SM, we obtain the
effective potential in the 2-loop approximation and investigate the existence
of its postulated second minimum at the fundamental scale. The investigation of
the evolution of the top quark Yukawa coupling constant in the 2-loop
approximation shows that, with initial values of the top Yukawa coupling in the
interval (here is the top quark pole mass), a
second minimum of the SM effective potential can exist in the region
GeV. A prediction is made of the existence
of a new bound state of 6 top quarks and 6 anti-top quarks, formed due to Higgs
boson exchanges between pairs of quarks/anti-quarks. This bound state is
supposed to condense in a new phase of the SM vacuum. This gives rise to the
possibility of having a phase transition between vacua with and without such a
condensate. The existence of three vacuum states (new, electroweak and
fundamental) solves the hierarchy problem in the SM.Comment: 30 pages, 7 figures; to be published in Phys. Atom. Nuc
Behavior of quantum entropies in polaronic systems
Quantum entropies and state distances are analyzed in polaronic systems with
short range (Holstein model) and long range (Frhlich model)
electron-phonon coupling. These quantities are extracted by a variational wave
function which describes very accurately polaron systems with arbitrary size in
all the relevant parameter regimes. With the use of quantum information tools,
the crossover region from weak to strong coupling regime can be characterized
with high precision. Then, the linear entropy is found to be very sensitive to
the range of the electron-phonon coupling and the adiabatic ratio. Finally, the
entanglement entropy is studied as a function of the system size pointing out
that it not bounded, but scales as the logarithm of the size either for weak
electron-phonon coupling or for short range interaction. This behavior is
ascribed to the peculiar coupling induced by the single electron itinerant
dynamics on the phonon subsystem.Comment: 4 figures, to be published in Phys. Rev.
Diphoton decay of the Higgs boson and new bound states of top and anti-top quarks
We consider the constraints, provided by the LHC results on Higgs boson decay
into 2 photons and its production via gluon fusion, on the previously proposed
Standard Model (SM) strongly bound state of 6 top quarks and 6 anti-top
quarks. A correlation is predicted between the ratios and
of the Higgs diphoton decay and gluon production amplitudes
respectively to their SM values. We estimate the contribution to these
amplitudes from one loop diagrams involving the 12 quark bound state and
related excited states using an atomic physics based model. We find two regions
of parameter space consistent with the ATLAS and CMS data on
(, ) at the 3 sigma level: a region close to the SM
values (, ) with the mass of the bound state
GeV and a region with (, ) corresponding to a bound state mass of GeV.Comment: 27 pages and 4 figure
Optimal control, geometry, and quantum computing
We prove upper and lower bounds relating the quantum gate complexity of a
unitary operation, U, to the optimal control cost associated to the synthesis
of U. These bounds apply for any optimal control problem, and can be used to
show that the quantum gate complexity is essentially equivalent to the optimal
control cost for a wide range of problems, including time-optimal control and
finding minimal distances on certain Riemannian, subriemannian, and Finslerian
manifolds. These results generalize the results of Nielsen, Dowling, Gu, and
Doherty, Science 311, 1133-1135 (2006), which showed that the gate complexity
can be related to distances on a Riemannian manifoldComment: 7 Pages Added Full Names to Author
Developing the Deutsch-Hayden approach to quantum mechanics
The formalism of Deutsch and Hayden is a useful tool for describing quantum
mechanics explicitly as local and unitary, and therefore quantum information
theory as concerning a "flow" of information between systems. In this paper we
show that these physical descriptions of flow are unique, and develop the
approach further to include the measurement interaction and mixed states. We
then give an analysis of entanglement swapping in this approach, showing that
it does not in fact contain non-local effects or some form of superluminal
signalling.Comment: 14 pages. Added section on entanglement swappin
Superconducting Spin Qubits
We propose and theoretically investigate spin superconducting qubits. Spin
superconducting qubit consists of a single spin confined in a Josephson
junction. We show that owing to spin-orbit interaction, superconducting
difference across the junction can polarize this spin. We demonstrate that this
enables single qubit operations and more complicated quantum gates, where spins
of different qubits interact via a mutual inductance of superconducting loop
where the junctions are embedded. Recent experimental realizations of Josephson
junctions made of semiconductor quantum dots in contact with superconducting
leads have shown that the number of electrons in the quantum dot can be tuned
by a gate voltage. Spin superconducting qubit is realized when the number of
electrons is odd. We discuss the qubit properties at phenomenological level. We
present a microscopic theory that enables us to make accurate estimations of
the qubit parameters by evaluating the spin-dependent Josephson energy in the
framework of fourth-order perturbation theory.Comment: 11 pages, 8 figure
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