846 research outputs found
Optimal simulation of two-qubit Hamiltonians using general local operations
We consider the simulation of the dynamics of one nonlocal Hamiltonian by
another, allowing arbitrary local resources but no entanglement nor classical
communication. We characterize notions of simulation, and proceed to focus on
deterministic simulation involving one copy of the system. More specifically,
two otherwise isolated systems and interact by a nonlocal Hamiltonian
. We consider the achievable space of Hamiltonians such
that the evolution can be simulated by the interaction
interspersed with local operations. For any dimensions of and , and any
nonlocal Hamiltonians and , there exists a scale factor such that
for all times the evolution can be simulated by acting for
time interspersed with local operations. For 2-qubit Hamiltonians and
, we calculate the optimal and give protocols achieving it. The optimal
protocols do not require local ancillas, and can be understood geometrically in
terms of a polyhedron defined by a partial order on the set of 2-qubit
Hamiltonians.Comment: (1) References to related work, (2) protocol to simulate one
two-qudit Hamiltonian with another, and (3) other related results added. Some
proofs are simplifie
A generalized no-broadcasting theorem
We prove a generalized version of the no-broadcasting theorem, applicable to
essentially \emph{any} nonclassical finite-dimensional probabilistic model
satisfying a no-signaling criterion, including ones with ``super-quantum''
correlations. A strengthened version of the quantum no-broadcasting theorem
follows, and its proof is significantly simpler than existing proofs of the
no-broadcasting theorem.Comment: 4 page
Interaction and observation: categorical semantics of reactive systems trough dialgebras
We use dialgebras, generalising both algebras and coalgebras, as a complement
of the standard coalgebraic framework, aimed at describing the semantics of an
interactive system by the means of reaction rules. In this model, interaction
is built-in, and semantic equivalence arises from it, instead of being
determined by a (possibly difficult) understanding of the side effects of a
component in isolation. Behavioural equivalence in dialgebras is determined by
how a given process interacts with the others, and the obtained observations.
We develop a technique to inter-define categories of dialgebras of different
functors, that in particular permits us to compare a standard coalgebraic
semantics and its dialgebraic counterpart. We exemplify the framework using the
CCS and the pi-calculus. Remarkably, the dialgebra giving semantics to the
pi-calculus does not require the use of presheaf categories
Ongoing methane discharge at well site 22/4b (North Sea)and discovery of a spiral vortex bubble plume motion
Highlights
• Mega ebullition of biogenic methane from an abandoned offshore gas well, North Sea.
• Evidence for midwater bubble plume intrusion, fallback, and short-circuiting of the plume.
• Effective trapping of seabed released methane underneath the thermocline.
• First observation of a spiral vortex methane plume and marginal turbulences.
• Megaplumes appear less efficient in terms of vertical methane transport than previously thought.
Abstract
First direct evidence for ongoing gas seepage activity on the abandoned well site 22/4b (Northern North Sea, 57°55′ N, 01°38′ E) and discovery of neighboring seepage activity is provided from observations since 2005. A manned submersible dive in 2006 discovered several extraordinary intense seepage sites within a 60 m wide and 20 m deep crater cut into the flat 96 m deep seafloor. Capture and (isotope) chemical analyses of the gas bubbles near the seafloor revealed in situ concentrations of methane between 88 and 90%Vol. with δ13C–CH4 values around −74‰ VPDB, indicating a biogenic origin. Bulk methane concentrations throughout the water column were assessed by 120 Niskin water samples showing up to 400.000 nM CH4 in the crater at depth. In contrast, concentrations above the thermocline were orders of magnitude lower, with a median value of 20 nM. A dye tracer injection into the gas seeps revealed upwelling bubble and water motion with gas plume rise velocities up to ∼1 ms−1 (determined near the seabed). However, the dissolved dye did not pass the thermocline, but returned down to the seabed. Measurements of direct bubble-mediated atmospheric flux revealed low values of 0.7 ± 0.3 kty−1, much less than current state-of-the-art bubble dissolution models would predict for such a strong and upwelling in situ gas bubble flux at shallow water depths (i.e. ∼100 m). Acoustic multibeam water column imaging data indicate a pronounced 200 m lateral intrusion at the thermocline together with high methane concentration at this layer. A partly downward-orientated bubble plume motion is also visible in the acoustic data with potential short-circuiting in accordance to the dye experiment. This observation could partly explain the observed trapping of most of the released gas below the well-established thermocline in the North Sea. Moreover, 3D analyses of the multibeam water column data reveal that the upwelling plume transforms into a spiral expanding vortex while rising through the water column. Such a spiral vortex motion has never been reported before for marine gas seepage and might represent an important process with strong implication on plume dynamics, dissolution behavior, gas escape to the atmosphere, and is considered very important for respective modeling approaches
Deriving Bisimulation Congruences: 2-categories vs precategories
G-relative pushouts (GRPOs) have recently been proposed by the authors as a new foundation for Leifer and Milner’s approach to deriving labelled bisimulation congruences from reduction systems. This paper develops the theory of GRPOs further, arguing that they provide a simple and powerful basis towards a comprehensive solution. As an example, we construct GRPOs in a category of ‘bunches and wirings.’ We then examine the approach based on Milner’s precategories and Leifer’s functorial reactive systems, and show that it can be recast in a much simpler way into the 2-categorical theory of GRPOs
Are quantum states real?
In this paper we consider theories in which reality is described by some
underlying variables. Each value these variables can take represents an ontic
state (a particular state of reality). The preparation of a quantum state
corresponds to a distribution over the ontic states. If we make three basic
assumptions, we can show that the distributions over ontic states corresponding
to distinct pure states are non-overlapping. This means that we can deduce the
quantum state from a knowledge of the ontic state. Hence, if these assumptions
are correct, we can claim that the quantum state is a real thing (it is written
into the underlying variables that describe reality). The key assumption we use
in this proof is ontic indifference - that quantum transformations that do not
affect a given pure quantum state can be implemented in such a way that they do
not affect the ontic states in the support of that state. In fact this
assumption is violated in the Spekkens toy model (which captures many aspects
of quantum theory and in which different pure states of the model have
overlapping distributions over ontic states). This paper proves that ontic
indifference must be violated in any model reproducing quantum theory in which
the quantum state is not a real thing. The argument presented in this paper is
different from that given in a recent paper by Pusey, Barrett, and Rudolph. It
uses a different key assumption and it pertains to a single copy of the system
in question.Comment: 19 pages, 4 figures. Remarks added concerning fact that ontic
indifference assumption is violated in Spekkens toy mode
Thermal decomposition of a fullerene mix
Experiments to characterize fullerene decomposition at temperatures above 973 K were conducted by spectroscopic analysis of samples heated in vacuo. The thermal decomposition can be described by first-order kinetics with an activation energy of 266±9 kJ/mol and a preexponential factor of 1.24×10^(9) s^-1. Though scanning electron micrographs display structures with a distinctly faceted appearance, x-ray diffraction, Raman spectroscopy, and transmission-electron microscopy all show that the material is composed of amorphous carbon and graphite, indicating that pyrolysis of the fullerite occurs without destroying crystal facets
UPAYA HUKUM KREDITOR PENERIMA JAMINAN FIDUSIA MOTOR BEKAS APABILA DEBITOR WANPRESTASI DAN BENDA JAMINAN MENGALAMI OVERMACHT PADA BRI SURAKARTA
Bank Rakyat Indonesia was established in Purwokerto, Central Java by Raden Aria
Wirjaatmadja under the name Hulp-en Spaarbank der Inlandsche Bertuurs Ambtenaren. Bank
Rakyat Indonesia is the first government bank in the Republic of Indonesia, established on
December 16, 1895. Fiduciary security is a guarantee that is often used because it has benefits
for both parties. In the world of financial institutions of the Bank, do not escape the existence
of an agreement between creditors as funders and debtors of recipients of funds. If the debtor
breaches the pledge or does not perform to the creditor but the collateral object experiences
a state of force majeure resulting in damaged or even destroyed objects that harm the creditor.
The method I use is to interview the head of Semanggi unit and supervisor BRI Surakarta.
Efforts made by BRI Unit Semanggi Surakarta with a persuasive approach with
debtors' obligations to keep paying off the debt even though the collateral objects overmach
in accordance with the accessoir principle and under article 1131 Civil Code. Another effort
by BRI Semanggi Unit to protect the bank from the risk is by filing insurance claim to PT.
Askrindo as the guarantor of the government for the financing of KUR BRI. Submission of
insurance claims can be made if the debtor does not perform achievements or installments
jammed more than 120 days from here there are other consequences that will arise that
collectibility of debtors will be bad that resulted in bad debtor can no longer apply credit to
banks and non-bank financial institutions that have become members of SLIK managed by
OJK
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