41,363 research outputs found
: An Excellent Candidate of Tetraquarks
We analyze various possible interpretations of the narrow state
which lies 100 MeV above threshold. This interesting state
decays mainly into instead of . If this relative branching
ratio is further confirmed by other experimental groups, we point out that the
identification of either as a state or more generally
as a state in the representation is probably
problematic. Instead, such an anomalous decay pattern strongly indicates
is a four quark state in the representation
with the quark content . We discuss its
partners in the same multiplet, and the similar four-quark states composed of a
bottom quark . Experimental searches of other members
especially those exotic ones are strongly called for
Classical simulation of quantum many-body systems with a tree tensor network
We show how to efficiently simulate a quantum many-body system with tree
structure when its entanglement is bounded for any bipartite split along an
edge of the tree. This is achieved by expanding the {\em time-evolving block
decimation} simulation algorithm for time evolution from a one dimensional
lattice to a tree graph, while replacing a {\em matrix product state} with a
{\em tree tensor network}. As an application, we show that any one-way quantum
computation on a tree graph can be efficiently simulated with a classical
computer.Comment: 4 pages,7 figure
Negative-Index Refraction in a Lamellar Composite with Alternating Single Negative Layers
Negative-index refraction is achieved in a lamellar composite with
epsilon-negative (ENG) and mu-negative (MNG) materials stacked alternatively.
Based on the effective medium approximation, simultaneously negative effective
permittivity and permeability of such a lamellar composite are obtained
theoretically and further proven by full-wave simulations. Consequently, the
famous left-handed metamaterial comprising split ring resonators and wires is
interpreted as an analogy of such an ENG-MNG lamellar composite. In addition,
beyond the effective medium approximation, the propagating field squeezed near
the ENG/MNG interface is demonstrated to be left-handed surface waves with
backward phase velocity.Comment: 18 pages, 6 figure
On quasi-local Hamiltonians in General Relativity
We analyse the definition of quasi-local energy in GR based on a Hamiltonian
analysis of the Einstein-Hilbert action initiated by Brown-York. The role of
the constraint equations, in particular the Hamiltonian constraint on the
timelike boundary, neglected in previous studies, is emphasized here. We argue
that a consistent definition of quasi-local energy in GR requires, at a
minimum, a framework based on the (currently unknown) geometric well-posedness
of the initial boundary value problem for the Einstein equations.Comment: 9 page
Light Fan Driven by a Relativistic Laser Pulse
When a relativistic laser pulse with a high photon density interacts with a specially tailored thin foil target, a strong torque is exerted on the resulting spiral-shaped foil plasma, or “light fan.” Because of its structure, the latter can gain significant orbital angular momentum (OAM), and the opposite OAM is imparted to the reflected light, creating a twisted relativistic light pulse. Such an interaction scenario is demonstrated by particle-in-cell simulation as well as analytical modeling, and should be easily verifiable in the laboratory. As an important characteristic, the twisted relativistic light pulse has a strong torque and ultrahigh OAM density
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Life cycle assessment of white roof and sedum-tray garden roof for office buildings in China
White roof (WR) and Sedum lineare tray garden roof (STGR) have been convinced to improve the energy-efficiency and provide various benefits for conventional impervious grey roofs. Some national and local standards have standardized and recommended these technologies in existing building retrofits, however, they do not include assessment and choice of a particular roof retrofit in different climates. This paper presents a 40-year life-cycle cost analysis (LCCA) of an office building roof retrofitted by adding either WR or STGR over an existing grey roof in five cities, located in four Chinese climate zones. The LCCA find that the WR retrofits exhibit positive life-cycle net savings (NS) in warm winter zones, ranging 5.7–35.1 CNY/m 2 , and STGR retrofits have negative NS of -81.3– -16.7 CNY/m 2 in all climate zones. The NS of both WR and STGR generally tend to improve as one moves from the coldest cities to the warmest cities. LCCA results suggest that adding new building codes concerning crediting or prescribing WR and STGR retrofits into office buildings with grey roofs in hot summer climate zones and warm winter zone in China, respectively. And featured by more specific requirements, the localized Technical Norms help promote the implementation of new building codes
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