13,262 research outputs found
The Static Quantum Multiverse
We consider the multiverse in the intrinsically quantum mechanical framework
recently proposed in Refs. [1,2]. By requiring that the principles of quantum
mechanics are universally valid and that physical predictions do not depend on
the reference frame one chooses to describe the multiverse, we find that the
multiverse state must be static---in particular, the multiverse does not have a
beginning or end. We argue that, despite its naive appearance, this does not
contradict observation, including the fact that we observe that time flows in a
definite direction. Selecting the multiverse state is ultimately boiled down to
finding normalizable solutions to certain zero-eigenvalue equations, analogous
to the case of the hydrogen atom. Unambiguous physical predictions would then
follow, according to the rules of quantum mechanics.Comment: 27 pages, 2 figures; a typo in the abstract correcte
Electric charging of magnetic textures on the surface of a topological insulator
A three-dimensional topological insulator manifests gapless surface modes,
described by two-dimensional Dirac equation. We study magnetic textures, such
as domain walls and vortices, in a ferromagnetic thin film deposited on a
three-dimensional topological insulator. It is shown that these textures can be
electrically charged, ascribed to the proximity effect with the Dirac surface
states. We derive a general relation between the electric and the magnetic
charges. As a physical consequence, we discuss domain wall motion driven by an
applied electric field, which promises magnetic devices with high thermal
efficiency.Comment: 5 pages, 2 figure
Inversion phenomenon and phase diagram of the distorted diamond chain with the interaction anisotropy
We discuss the anisotropies of the Hamiltonian and the wave-function in an
distorted diamond chain. The ground-state phase diagram of this model
is investigated using the degenerate perturbation theory up to the first order
and the level spectroscopy analysis of the numerical diagonalization data. In
some regions of the obtained phase diagram, the anisotropy of the Hamiltonian
and that of the wave-function are inverted, which we call inversion phenomenon;
the N\'{e}el phase appears for the XY-like anisotropy and the spin-fluid phase
appears for the Ising-like anisotropy. Three key words are important for this
nature, which are frustration, the trimer nature, and the anisotropy.Comment: 4pages, 10 figures, for proceedings of SPQS 200
Level spectroscopy of the square-lattice three-state Potts model with a ferromagnetic next-nearest-neighbor coupling
We study the square-lattice three-state Potts model with the ferromagnetic
next-nearest-neighbor coupling at finite temperature. Using the
level-spectroscopy method, we numerically analyze the excitation spectrum of
the transfer matrices and precisely determine the global phase diagram. Then we
find that, contrary to a previous result based on the finite-size scaling, the
massless region continues up to the decoupling point with criticality in the antiferromagnetic region. We also check the universal
relations among excitation levels to provide the reliability of our result.Comment: 4 pages, 2 figure
Theory of electric polarization in multi-orbital Mott insulators
The interaction between the electric field, E, and spins in multi-orbital
Mott insulators is studied theoretically. We find a generic dynamical coupling
mechanism, which works for all crystal lattices and which does not involve
relativistic effects. The general form of the coupling is -T_ab E_a e_b, where
e is the `internal' electric field originating from the dynamical Berry phase
of electrons and T_ab is a tensor determined by lattice symmetry. We discuss
several effects of this interaction: (i) an unusual electron spin resonance
induced by an oscillating electric field, (ii) the displacement of spin
textures in an applied electric field, and (iii) the resonant absorption of
circularly polarized light by Skyrmions, magnetic bubbles, and magnetic
vortices.Comment: 5 page
Supersymmetry, Naturalness, and Signatures at the LHC
Weak scale supersymmetry is often said to be fine-tuned, especially if the
matter content is minimal. This is not true if there is a large A term for the
top squarks. We present a systematic study on fine-tuning in minimal
supersymmetric theories and identify low energy spectra that do not lead to
severe fine-tuning. Characteristic features of these spectra are: a large A
term for the top squarks, small top squark masses, moderately large tan\beta,
and a small \mu parameter. There are classes of theories leading to these
features, which are discussed. In one class, which allows a complete
elimination of fine-tuning, the Higgsinos are the lightest among all the
superpartners of the standard model particles, leading to three nearly
degenerate neutralino/chargino states. This gives interesting signals at the
LHC -- the dilepton invariant mass distribution has a very small endpoint and
shows a particular shape determined by the Higgsino nature of the two lightest
neutralinos. We demonstrate that these signals are indeed useful in realistic
analyses by performing Monte Carlo simulations, including detector simulations
and background estimations. We also present a method that allows the
determination of all the relevant superparticle masses without using input from
particular models, despite the limited kinematical information due to short
cascades. This allows us to test various possible models, which is demonstrated
in the case of a model with mixed moduli-anomaly mediation. We also give a
simple derivation of special renormalization group properties associated with
moduli mediated supersymmetry breaking, which are relevant in a model without
fine-tuning.Comment: 56 pages, 24 figure
The q-harmonic oscillators, q-coherent states and the q-symplecton
The recently introduced notion of a quantum group is discussed conceptually and then related to deformed harmonic oscillators ('q-harmonic oscillators'). Two developments in applying q-harmonic oscillators are reviewed: q-coherent states and the q-symplecton
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