In this article, we choose the
s
c
P
s
¯
c
¯
A
-
s
c
A
s
¯
c
¯
P
type tetraquark current to study the hadronic coupling constants in the strong decays
Y
(
4660
)
→
J
/
ψ
f
0
(
980
)
,
η
c
ϕ
(
...1020
)
,
χ
c
0
ϕ
(
1020
)
,
D
s
D
¯
s
,
D
s
∗
D
¯
s
∗
,
D
s
D
¯
s
∗
,
D
s
∗
D
¯
s
,
ψ
′
π
+
π
-
,
J
/
ψ
ϕ
(
1020
)
with the QCD sum rules based on solid quark-hadron quality. The predicted width
Γ
(
Y
(
4660
)
)
=
74
.
2
-
19.2
+
29.2
MeV
is in excellent agreement with the experimental data
68
±
11
±
1
MeV
from the Belle collaboration, which supports assigning the
Y
(4660) to be the
s
c
P
s
¯
c
¯
A
-
s
c
A
s
¯
c
¯
P
type tetraquark state with
J
PC
=
1
-
-
. In calculations, we observe that the hadronic coupling constants
|
G
Y
ψ
′
f
0
|
≫
|
G
Y
J
/
ψ
f
0
|
, which is consistent with the observation of the
Y
(4660) in the
ψ
′
π
+
π
-
mass spectrum, and favors the
ψ
′
f
0
(
980
)
molecule assignment. It is important to search for the process
Y
(
4660
)
→
J
/
ψ
ϕ
(
1020
)
to diagnose the nature of the
Y
(4660), as the decay is greatly suppressed.
Using the spillover index approach and its variants, we examine both static and dynamic volatility connectedness among eight typical cryptocurrencies. The results reveal that their connectedness ...fluctuates cyclically and has shown an obvious rise trend since the end of 2016. In the variance decomposition framework, we further construct a volatility connectedness network linking 52 cryptocurrencies using the LASSO-VAR for estimating high-dimensional VARs. We find that these 52 cryptocurrencies are tightly interconnected and “mega-cap” cryptocurrencies are more likely to propagate volatility shocks to others. However, some unnoticeable cryptocurrencies (e.g., Maidsafe Coin) are also significant net-transmitters of volatility connectedness and even have larger contribution of volatility spillovers to others.
•Total connectedness of 8 cryptocurrencies fluctuates periodically and increases from end-2016 onwards.•Volatility connectedness network of 52 cryptocurrencies is built and analyzed.•The level of incoming or outgoing connectedness of a cryptocurrency is partly linked to its market cap.•Bitcoin is proved to be an important net-emitter of connectedness but not the dominant one.•Some unnoticeable cryptocurrencies (e.g., Maidsafe Coin) also transmit strong volatility shocks to others.
Abstract The current industrial ammonia synthesis relies on Haber–Bosch process that is initiated by the dissociative mechanism, in which the adsorbed N 2 dissociates directly, and thus is limited by ...Brønsted–Evans–Polanyi (BEP) relation. Here we propose a new strategy that an anchored Fe 3 cluster on the θ-Al 2 O 3 (010) surface as a heterogeneous catalyst for ammonia synthesis from first-principles theoretical study and microkinetic analysis. We have studied the whole catalytic mechanism for conversion of N 2 to NH 3 on Fe 3 /θ-Al 2 O 3 (010), and find that an associative mechanism, in which the adsorbed N 2 is first hydrogenated to NNH, dominates over the dissociative mechanism, which we attribute to the large spin polarization, low oxidation state of iron, and multi-step redox capability of Fe 3 cluster. The associative mechanism liberates the turnover frequency (TOF) for ammonia production from the limitation due to the BEP relation, and the calculated TOF on Fe 3 /θ-Al 2 O 3 (010) is comparable to Ru B5 site.
A
bstract
Our understanding of quantum correlators in cosmological spacetimes, including those that we can observe in cosmological surveys, has improved qualitatively in the past few years. Now we ...know many constraints that these objects must satisfy as consequences of general physical principles, such as symmetries, unitarity and locality. Using this new understanding, we derive the most general scalar four-point correlator, i.e., the trispectrum,
to all orders in derivatives
for manifestly local
contact
interactions. To obtain this result we use techniques from commutative algebra to write down all possible scalar four-particle amplitudes without assuming invariance under Lorentz boosts. We then input these amplitudes into a
contact reconstruction formula
that generates a contact cosmological correlator in de Sitter spacetime from a contact scalar or graviton amplitude. We also show how the same procedure can be used to derive higher-point contact cosmological correlators. Our results further extend the reach of the boostless cosmological bootstrap and build a new connection between flat and curved spacetime physics.
In the article, we investigate the diquark-diquark-antiquark type fully-heavy pentaquark states with the spin-parity JP=12− via the QCD sum rules for the first time, and obtain the masses ...Mccccc¯=7.93±0.15 GeV and Mbbbbb¯=23.91±0.15 GeV. We can search for the fully-heavy pentaquark states in the J/ψΩccc and ϒΩbbb invariant mass spectrum in the future.
In this article, we construct the
C
⊗
γ
μ
C
and
C
γ
5
⊗
γ
5
γ
μ
C
type currents to interpolate the vector tetraquark states, then carry out the operator product expansion up to the vacuum condensates ...of dimension-10 in a consistent way, and obtain four QCD sum rules. In calculations, we use the formula
μ
=
M
Y
2
-
(
2
M
c
)
2
to determine the optimal energy scales of the QCD spectral densities, moreover, we take the experimental values of the masses of the
Y
(4260 / 4220),
Y
(4360 / 4320),
Y
(4390) and
Y
(4660 / 4630) as input parameters and fit the pole residues to reproduce the correlation functions at the QCD side. The numerical results support assigning the
Y
(4660 / 4630) to be the
C
⊗
γ
μ
C
type vector tetraquark state
c
c
¯
s
s
¯
, assigning the
Y
(4360 / 4320) to be
C
γ
5
⊗
γ
5
γ
μ
C
type vector tetraquark state
c
c
¯
q
q
¯
, and disfavor assigning the
Y
(4260 / 4220) and
Y
(4390) to be the pure vector tetraquark states.
In the present work, we adopt the scalar, pseudoscalar, vector, axialvector and tensor (anti)diquark operators as the elementary building blocks to construct vector and tensor local four-quark ...currents without introducing explicit P-waves, and explore the mass spectrum of the vector hidden-charm tetraquark states via the QCD sum rules comprehensively, and revisit the interpretations of the existing Y states in the scenario of vector tetraquark states. We resort to the energy scale formula to enhance the pole contributions and improve the convergent behaviors of the operator product expansion, and we should bear in mind that the predictions are rather sensitive to the particular energy scales which obey the uniform/same constraint. The predicted vector hidden-charm tetraquark states can be confronted to the experimental data in the future.
We take the scalar, pseudoscalar, axialvector, vector and tensor diquarks as the basic building blocks to construct the four-quark currents with implicit P-waves, and investigate the ...hidden-charm-hidden-strange tetraquark states with the JPC=1−− and 1−+ via the QCD sum rules in a comprehensive and consistent way, and revisit the assignments of the X/Y states, especially the Y(4500), X(4630), Y(4660), Y(4710) and Y(4790), in the tetraquark picture.
In this article, we extend our previous work to study the mass spectrum of the ground state hidden-bottom tetraquark states with the QCD sum rules in a systematic way. The predicted hidden-bottom ...tetraquark masses can be confronted to the experimental data in the future to diagnose the nature of the
Z
b
states. In calculations, we observe that the scalar diquark states, the axialvector diquark states and the axialvector components of the tensor diquark state are all good diquarks in building the lowest tetraquark states.
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