32,912 research outputs found
The Price of Governance: A Middle Ground Solution to Coordination in Organizational Control
Achieving coordination is crucial in organizational control. This paper
investigates a middle ground solution between decentralized interactions and
centralized administrations for coordinating agents beyond inefficient
behavior. We first propose the price of governance (PoG) to evaluate how such a
middle ground solution performs in terms of effectiveness and cost. We then
propose a hierarchical supervision framework to explicitly model the PoG, and
define step by step how to realize the core principle of the framework and
compute the optimal PoG for a control problem. Two illustrative case studies
are carried out to exemplify the applications of the proposed framework and its
methodology. Results show that by properly formulating and implementing each
step, the hierarchical supervision framework is capable of promoting
coordination among agents while bounding administrative cost to a minimum in
different kinds of organizational control problems
Higher ramification loci over homogeneous spaces
We generalize the Gaffney-Lazarsfeld theorem on higher ramification loci of
branched coverings of to homogeneous spaces with Picard number
one.Comment: 7 page
Three Identical Fermions with Resonant p-wave Interactions in Two Dimensions
A new kind of "super-Efimov" states of binding energies scaling as
were predicted by a field theory calculation for
three fermions with resonant -wave interactions in two dimensions [Phys.
Rev. Lett. \textbf{110}, 235301 (2013)]. However, the universality of these
"super-Efimov" states has not been proved independently. In this Letter, we
study the three fermion system through the hyperspherical formalism. Within the
adiabatic approximation, we find that at -wave resonances, the low energy
physics of states of angular momentum crucially depends on the
value of an emergent dimensionless parameter determined by the detail of
the inter-particle potential. Only if is exactly zero, the predicted
"super-Efimov" states exist. If , the scaling of the bound states changes
to , while there are no shallow bound states if
.Comment: The neglected term has been calculated numerically and found
to be non-negligible in the large hyperradius limi
Breathing mode of two-dimensional atomic Fermi gases in harmonic traps
For two-dimensional (2D) atomic Fermi gases in harmonic traps, the SO(2,1)
symmetry is broken by the interatomic interaction explicitly via the contact
correlation operator. Consequently the frequency of the breathing mode
of the 2D Fermi gas can be different from , with
the trapping frequency of harmonic potentials. At zero temperature,
we use the sum rules of density correlation functions to yield upper bounds for
. We further calculate through the Euler equations in the
hydrodynamic regime. The obtained value of satisfies the upper
bounds and shows deviation from which can be as large as about 8%.Comment: 5 pages, 1 figur
The Single Particle Excitation Spectrum of Degenerate Fermi gases in a ring cavity
By considering a spin- degenerate Fermi gases in a ring cavity
where strong interaction between atoms and light gives rise to a superradiance,
we find the cavity dissipation could cause a severe broadening in some special
cases, breaking down the quasi-particle picture which was constantly assumed in
mean field theory studies. This broadening happens when the band gap resonant
with polariton excitation energy. Interestingly enough, this broadening is
highly spin selective depending on how the fermions are filled and the spectrum
becomes asymmetric due to dissipation. Further, a non-monotonous dependence of
the maximal broadening of the spectrum against cavity decay rate is
found and the largest broadening emerges at comparable to recoil
energy.Comment: 10 pages, 10 figure
Density Wave Superradiance of Photonic Fluid in Frustrated Triangle Lattice Cavity Arrays
The spontaneously broken of translational symmetry is usually due to the
competition between local interactions and long-range interactions. However, in
this paper, we show how a crystalline order can be generated by the competition
between local interaction and long-range correlation by frustration. Here we
propose a positive hopping Bose Hubbard model on triangle lattices with a pair
creation term which comes from frustrated linked cavity arrays with degenerate
quantum gases in them. We find by increasing the strength of pair creation term
against local interaction strength, two kinds of density wave ordered
superradiant photonic fluid phase can be realized and a first order transition
between two different density wave ordered states is found. This proposal shows
us a new way to produce coherent "solid" phase without the help of long range
interactions.Comment: 5 pages, 4 figure
Piezoelectricity and Topological Quantum Phase Transitions in Two-Dimensional Spin-Orbit Coupled Crystals with Time-Reversal Symmetry
Finding new physical responses that signal topological quantum phase
transitions is of both theoretical and experimental importance. Here, we
demonstrate that the piezoelectric response can change discontinuously across a
topological quantum phase transition in two-dimensional time-reversal invariant
systems with spin-orbit coupling, thus serving as a direct probe of the
transition. We study all gap closing cases for all 7 plane groups that allow
non-vanishing piezoelectricity and find that any gap closing with 1 fine-tuning
parameter between two gapped states changes either the invariant or the
locally stable valley Chern number. The jump of the piezoelectric response is
found to exist for all these transitions, and we propose the HgTe/CdTe quantum
well and BaMnSb as two potential experimental platforms. Our work provides
a general theoretical framework to classify topological quantum phase
transitions and reveals their ubiquitous relation to the piezoelectric
response.Comment: Close to the published versio
Note on acoustic black holes from black D3-brane
In this paper, we study the acoustic black hole emerged from the nonextremal
black D3-brane, based on the holographic approaches in constructing the
acoustic black hole in asymptotically Anti de-Sitter spacetime (AAdS) and the
effective hydrodynamic description of the nonextremal black D3-brane. We show
that the holographic dual description of the acoustic black hole appeared on
the timelike cutoff surface in the nonextremal black D3-brane also exist. The
duality includes the dynamical connection between the acoustic black hole and
the bulk gravity, a universal equation relating the Hawking-like temperature
and the Hawking temperature, and a phonon/scalar channel quasinormal mode
correspondence.Comment: 14 pages, no figure
Spin Susceptibility, Upper Critical Field and Disorder Effect in Superconductors with Singlet-Quintet Mixing
Recently, a new pairing state with the mixing between s-wave singlet channel
and isotropic d-wave quintet channel induced by centrosymmetric spin-orbit
coupling has been theoretically proposed in the superconducting materials with
electrons. In this work, we derive the expressions of the
zero-temperature spin susceptibility, the upper critical field close to the
zero-field critical temperature and the critical temperature with weak
random non-magnetic disorders for the singlet-quintet mixed state based on the
Luttinger model. Our study revealed the following features of the
singlet-quintet mixing. (1) The zero-temperature spin susceptibility remains
zero for the singlet-quintet mixed state if only the centrosymmetric spin-orbit
coupling is taken into account, and will deviate from zero when the
non-centrosymmetric spin-orbit coupling is introduced. (2) The singlet-quintet
mixing can help enhance the upper critical field roughly because it can
increase . (3) Although the quintet channel is generally suppressed by the
non-magnetic disorder scattering, we find the strong mixing between singlet and
quintet channels can help to stabilize the quintet channel. As a result, we
still find a sizable quintet component mixed into the singlet channel in the
presence of weak random non-magnetic disorders. Our work provides the guidance
for future experiments on spin susceptibility and upper critical field of the
singlet-quintet mixed superconducting states, and illustrates the stability of
the singlet-quintet mixing against the weak random non-magnetic disorder.Comment: 23 pages and 6 figure
Gravitational waves and extra dimensions: a short review
We give a brief review on the recent development of gravitational waves in
extra-dimensional theories of gravity. Studying extra-dimensional theories with
gravitational waves provides a new way to constrain extra dimensions. After a
flash look at the history of gravitational waves and a brief introduction to
several major extra-dimensional theories, we focus on the sources and spectra
of gravitational waves in extra-dimensional theories. It is shown that one can
impose limits on the size of extra dimensions and the curvature of the universe
by researching the propagations of gravitational waves and the corresponding
electromagnetic waves. Since gravitational waves can propagate throughout the
bulk, how the amplitude of gravitational waves decreases determines the number
of extra dimensions for some models. In addition, we also briefly present some
other characteristics of gravitational waves in extra-dimensional theories.Comment: 35 pages, 1 figur
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