This article proposes a dynamic model to examine the structure of “simple” relational contracts, obeying realistic properties that can be easily understood and audited by both parties. In such ...relationships, the need to offer each supplier a large enough share of future business to deter cheating limits the number of relationships a buyer can sustain. Trade is thus restricted to durable relationships, a form of social capital. Nevertheless, exogenous stochastic shocks sometimes prevent suppliers from fulfilling their promises and relationships are constantly dissolving and later renewed. Moreover, the coming of a crisis, where stochastic shocks are more probable, can lead to the quick rupture of some relationships as there is less expected future business to incentivize all suppliers. New relationships can later be formed, but this takes time due to search frictions. This suggests new connections between the theory of relational contracting and the macroeconomic analysis of recessions.
We develop a dynamic model where successive, decentralized policy makers must decide whether to implement affirmative action policies aimed at improving the performance of future generations of a ...targeted group. Employers do not perfectly observe if a worker benefited from affirmative action, but take that possibility into account, resulting in the devaluation of the worker’s credentials and an associated feeling of injustice. We establish that, in equilibrium, affirmative action is implemented perpetually by benevolent policy makers, despite the feeling of injustice that eventually dominates the anticipated benefits. This contrasts with the first best, which requires affirmative action to be temporary.
Mapping states with explicit gluonic degrees of freedom in the light sector is a challenge, and has led to controversies in the past. In particular, the experiments have reported two different hybrid ...candidates with spin-exotic signature, π_{1}(1400) and π_{1}(1600), which couple separately to ηπ and η^{'}π. This picture is not compatible with recent Lattice QCD estimates for hybrid states, nor with most phenomenological models. We consider the recent partial wave analysis of the η^{(')}π system by the COMPASS Collaboration. We fit the extracted intensities and phases with a coupled-channel amplitude that enforces the unitarity and analyticity of the S matrix. We provide a robust extraction of a single exotic π_{1} resonant pole, with mass and width 1564±24±86 and 492±54±102 MeV, which couples to both η^{(')}π channels. We find no evidence for a second exotic state. We also provide the resonance parameters of the a_{2}(1320) and a_{2}^{'}(1700).
We study the nature of the new signal reported by LHCb in the J/ψp spectrum. Based on the S-matrix principles, we perform a minimum-bias analysis of the underlying reaction amplitude, focusing on the ...analytic properties that can be related to the microscopic origin of the Pc(4312)+ peak. By exploring several amplitude parametrizations, we find evidence for the attractive effect of the Σc+D¯0 channel, which is not strong enough, however, to form a bound state.
Three-body scattering: ladders and resonances Mikhasenko, M.; Wunderlich, Y.; Jackura, A. ...
The journal of high energy physics,
08/2019, Letnik:
2019, Številka:
8
Journal Article
Recenzirano
Odprti dostop
A
bstract
We discuss unitarity constraints on the dynamics of a system of three interacting particles. We show how the short-range interaction that describes three-body resonances can be separated ...from the long-range exchange processes, in particular the one-pion-exchange process. It is demonstrated that unitarity demands a specific functional form of the amplitude with a clear interpretation: the bare three-particle resonances are dressed by the initial- and final-state interaction, in a way that is consistent with the considered long-range forces. We postulate that the resonance kernel admits a factorization in the energy variables of the initial- and the final-state particles. The factorization assumption leads to an algebraic form for the unitarity equations, which is reminiscent of the well-known two-body-unitarity condition and approaches it in the limit of the narrow-resonance approximation.
In view of the recent high-statistic KLOE data for the η→π+π−π0 decay, a new determination of the quark mass double ratio has been done. Our approach relies on a dispersive model that takes into ...account rescattering effects between three pions via subenergy unitarity. The latter is essential to reproduce the Dalitz plot distribution. A simultaneous description of the KLOE and WASA-at-COSY data is achieved in terms of just two real parameters. From a global fit, we determine Q=21.6±1.1. The predicted slope parameter for the neutral channel α=−0.025±0.004 is in reasonable agreement with the PDG average value.
Swallowing is a complex physiological process transporting food from the mouth into the esophagus. Understanding how food properties condition flow, ease of swallowing and amount of post-swallow ...residues can support the design and development of novel products with improved texture and swallow-ability. Diagnostics allowed visualizing directly the effect of bolus consistency on flow, but complementary approaches are needed to speed up the pace of product innovation.
This review summarizes the state of the art with respect to the in vitro and in silico approaches to predict the ease of swallowing, with an overview of the oral, pharyngeal and esophageal swallowing. Physical and computational models are discussed and compared, highlighting capabilities and limitations.
In vitro and in silico experiments represent attractive complements to the in vivo investigations because they allow varying parameters independently, which is key to understand the effect of different food and drink properties and to adapting them to different needs. Two motor control strategies are commonly used, namely imposing displacements or stresses. These models have helped clarifying the role of bolus rheology in the oral phase of swallowing and the importance of salivary coating in the pharyngeal bolus flow. Few areas of improvements were identified: the use of more realistic geometries and mechanical properties representing the relevant tissues, of lubrication boundary conditions and of a wider variety of food boli. Further clinical studies should also focus on identifying the most realistic motor control strategy to mimic human swallowing.
•In vitro and in silico models to predict the ease of swallowing are discussed.•The relevant physiology, bolus and tissue properties are introduced.•The oral, pharyngeal and esophageal phases of swallowing are considered.•Different swallow motor control scenarios are discussed.•Limitations of existing models and future research opporunities are reviewed.
We perform a systematic analysis of the
J
/
ψ
→
γ
π
0
π
0
and
→
γ
K
S
0
K
S
0
partial waves measured by BESIII. We use a large set of amplitude parametrizations to reduce the model bias. We determine ...the physical properties of seven scalar and tensor resonances in the 1–
2.5
GeV
mass range. These include the well known
f
0
(
1500
)
and
f
0
(
1710
)
, that are considered to be the primary glueball candidates. The hierarchy of resonance couplings determined from this analysis favors the latter as the one with the largest glueball component.
The microscopic nature of the XYZ states remains an unsettled topic. We show how a thorough amplitude analysis of the data can help constraining models of these states. Specifically, we consider the ...case of the Zc(3900) peak and discuss possible scenarios of a QCD state, virtual state, or a kinematical enhancement. We conclude that current data are not precise enough to distinguish between these hypotheses, however, the method we propose, when applied to the forthcoming high-statistics measurements should shed light on the nature of these exotic enhancements.
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