34,891 research outputs found
A simpel and versatile cold-atom simulator of non-Abelian gauge potentials
We show how a single, harmonically trapped atom in a tailored magnetic field
can be used for simulating the effects of a broad class of non-abelian gauge
potentials. We demonstrate how to implement Rashba or Linear-Dresselhaus
couplings, or observe {\em Zitterbewegung} of a Dirac particle.Comment: 5 page
Creation of Entanglement by Interaction with a Common Heat Bath
I show that entanglement between two qubits can be generated if the two
qubits interact with a common heat bath in thermal equilibrium, but do not
interact directly with each other. In most situations the entanglement is
created for a very short time after the interaction with the heat bath is
switched on, but depending on system, coupling, and heat bath, the entanglement
may persist for arbitrarily long times. This mechanism sheds new light on the
creation of entanglement. A particular example of two quantum dots in a closed
cavity is discussed, where the heat bath is given by the blackbody radiation.Comment: 4 revtex pages, 1 eps figure; replaced with published version; short
discussion on entanglement distillation adde
Lubricated friction between incommensurate substrates
This paper is part of a study of the frictional dynamics of a confined solid
lubricant film - modelled as a one-dimensional chain of interacting particles
confined between two ideally incommensurate substrates, one of which is driven
relative to the other through an attached spring moving at constant velocity.
This model system is characterized by three inherent length scales; depending
on the precise choice of incommensurability among them it displays a strikingly
different tribological behavior. Contrary to two length-scale systems such as
the standard Frenkel-Kontorova (FK) model, for large chain stiffness one finds
that here the most favorable (lowest friction) sliding regime is achieved by
chain-substrate incommensurabilities belonging to the class of non-quadratic
irrational numbers (e.g., the spiral mean). The well-known golden mean
(quadratic) incommensurability which slides best in the standard FK model shows
instead higher kinetic-friction values. The underlying reason lies in the
pinning properties of the lattice of solitons formed by the chain with the
substrate having the closest periodicity, with the other slider.Comment: 14 pagine latex - elsart, including 4 figures, submitted to Tribology
Internationa
Hadron-nucleus scattering in the local reggeon model with pomeron loops for realistic nuclei
Contribution of simplest loops for hadron-nucleus scattering cross-sections
is studied in the Local Reggeon Field Theory with a supercritical pomeron. It
is shown that inside the nucleus the supercritical pomeron transforms into a
subcritical one, so that perturbative treatment becomes possible. The pomeron
intercept becomes complex, which leads to oscillations in the cross-sections.Comment: 13 pages, 6 figure
Three Generations on the Quintic Quotient
A three-generation SU(5) GUT, that is 3x(10+5bar) and a single 5-5bar pair,
is constructed by compactification of the E_8 heterotic string. The base
manifold is the Z_5 x Z_5-quotient of the quintic, and the vector bundle is the
quotient of a positive monad. The group action on the monad and its
bundle-valued cohomology is discussed in detail, including topological
restrictions on the existence of equivariant structures. This model and a
single Z_5 quotient are the complete list of three generation quotients of
positive monads on the quintic.Comment: 19 pages, LaTeX. v2: section on anomaly cancellation adde
The Exact MSSM Spectrum from String Theory
We show the existence of realistic vacua in string theory whose observable
sector has exactly the matter content of the MSSM. This is achieved by
compactifying the E_8 x E_8 heterotic superstring on a smooth Calabi-Yau
threefold with an SU(4) gauge instanton and a Z_3 x Z_3 Wilson line.
Specifically, the observable sector is N=1 supersymmetric with gauge group
SU(3)_C x SU(2)_L x U(1)_Y x U(1)_{B-L}, three families of quarks and leptons,
each family with a right-handed neutrino, and one Higgs-Higgs conjugate pair.
Importantly, there are no extra vector-like pairs and no exotic matter in the
zero mode spectrum. There are, in addition, 6 geometric moduli and 13 gauge
instanton moduli in the observable sector. The holomorphic SU(4) vector bundle
of the observable sector is slope-stable.Comment: 15 pages, LaTeX; v2: Hidden sector is unstable, symbol typesetting
error corrected, clarifications and references added; v3: New discussion of
hidden secto
Zero-temperature equation of state of mass-imbalanced resonant Fermi gases
We calculate the zero-temperature equation of state of mass-imbalanced
resonant Fermi gases in an ab initio fashion, by implementing the recent
proposal of imaginary-valued mass difference to bypass the sign problem in
lattice Monte Carlo calculations. The fully non-perturbative results thus
obtained are analytically continued to real mass imbalance to yield the
physical equation of state, providing predictions for upcoming experiments with
mass-imbalanced atomic Fermi gases. In addition, we present an exact relation
for the rate of change of the equation of state at small mass imbalances,
showing that it is fully determined by the energy of the mass-balanced system.Comment: 5 pages, 2 figures, 2 table
Inhomogeneous phases in one-dimensional mass- and spin-imbalanced Fermi gases
We compute the phase diagram of strongly interacting fermions in one
dimension at finite temperature, with mass and spin imbalance. By including the
possibility of the existence of a spatially inhomogeneous ground state, we find
regions where spatially varying superfluid phases are favored over homogeneous
phases. We obtain estimates for critical values of the temperature, mass and
spin imbalance, above which these phases disappear. Finally, we show that an
intriguing relation exists between the general structure of the phase diagram
and the binding energies of the underlying two-body bound-state problem.Comment: 5 pages, 3 figure
Phase structure of mass- and spin-imbalanced unitary Fermi gases
We study the phase diagram of mass- and spin-imbalanced unitary Fermi gases,
in search for the emergence of spatially inhomogeneous phases. To account for
fluctuation effects beyond the mean-field approximation, we employ
renormalization group techniques. We thus obtain estimates for critical values
of the temperature, mass and spin imbalance, above which the system is in the
normal phase. In the unpolarized, equal-mass limit, our result for the critical
temperature is in accordance with state-of-the-art Monte Carlo calculations. In
addition, we estimate the location of regions in the phase diagram where
inhomogeneous phases are likely to exist. We show that an intriguing relation
exists between the general structure of the many-body phase diagram and the
binding energies of the underlying two-body bound-state problem, which further
supports our findings. Our results suggest that inhomogeneous condensates form
for mass ratios of the spin-down and spin-up fermions greater than three. The
extent of the inhomogeneous phase in parameter space increases with increasing
mass imbalance.Comment: 17 pages, 7 figure
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