8,153 research outputs found
Singular limits of reaction diffusion equations and geometric flows with discontinuous velocity
We consider the singular limit of a bistable reaction diffusion equation in
the case when the velocity of the traveling wave solution depends on the space
variable and converges to a discontinuous function. We show that the family of
solutions converges to the stable equilibria off a front propagating with a
discontinuous velocity. The convergence is global in time by applying the weak
geometric flow uniquely defined through the theory of viscosity solutions and
the level-set equation
Walking, Weak first-order transitions, and Complex CFTs II. Two-dimensional Potts model at
We study complex CFTs describing fixed points of the two-dimensional
-state Potts model with . Their existence is closely related to the
weak first-order phase transition and walking RG behavior present in the real
Potts model at . The Potts model, apart from its own significance, serves
as an ideal playground for testing this very general relation. Cluster
formulation provides nonperturbative definition for a continuous range of
parameter , while Coulomb gas description and connection to minimal models
provide some conformal data of the complex CFTs. We use one and two-loop
conformal perturbation theory around complex CFTs to compute various properties
of the real walking RG flow. These properties, such as drifting scaling
dimensions, appear to be common features of the QFTs with walking RG flows, and
can serve as a smoking gun for detecting walking in Monte Carlo simulations.
The complex CFTs discussed in this work are perfectly well defined, and can
in principle be seen in Monte Carlo simulations with complexified coupling
constants. In particular, we predict a pair of -symmetric complex CFTs
with central charges describing the fixed points
of a 5-state dilute Potts model with complexified temperature and vacancy
fugacity.Comment: 34 pages, 13 figures. v2: refs added; v3 refs added, typos corrected,
presentation of several arguments clarifie
Importance of documentary credit in international trade: analysis of risk and prevention measures
Dissertação de mestrado em International BusinessIn international trade settlement, letters of credit (documentary credit), documentary
collections, and remittances are generally accepted international settlement methods. Letters
of credit take the leading position, with the characteristics of bank credit and the reciprocal
rights and obligations of buyer and seller. It has the function of guaranteeing security to both
exporters and importers; therefore, it is relatively safe means of settlement, which guarantees
the adequate functioning of international transactions. However, due to their characteristics,
letters of credit are not exempt from risks in their practical application. Therefore, the study of
the risk and preventive measures of the letter of credit has a strong relevance to the practice of
international trade.
This dissertation mainly analyzes the risk that the applicant, the bank (issuing bank and
negotiating bank) and the beneficiary may face in the process of using the credit, and puts
forward the corresponding risk prevention measures. Using a qualitative approach, we found a
unique perspective and new findings on the risk and risk prevention measures. The results of
this exploratory study suggest that there is a consensus in considering the principle of letter of
credit independence as one of its main sources of risk. This consensus suggests that future
development of the letter of credit involves reducing their independence, without completely
losing its independence essence. The evolution of letters of credit may also include the
cooperative development of operations and the use of digital platforms to facilitate the
investigation of the credibility of business partners.No comércio internacional, letras de crédito (crédito documentário), cobranças documentárias e
remessas são os métodos de pagamento geralmente aceites. A letra de crédito assume a
posição de liderança enquanto forma de pagamento no comércio internacional com as
características do crédito bancário e os direitos e obrigações recíprocos do comprador e do
vendedor. Tem a função de garantir a segurança a importadores e exportadores, sendo uma
forma de liquidação relativamente segura, que garante a condução normal das transações
internacionais. No entanto, pelas suas características, as letras de crédito não estão isentas de
risco na sua aplicação prática. Portanto, o estudo do risco e das medidas preventivas do risco
da carta de crédito tem uma forte relevância para a prática comercial internacional. Esta
dissertação analisa principalmente o risco que o ordenador (comprador), os bancos (banco
emitente e banco negociador) e o beneficiário (vendedor) podem enfrentar no processo de
utilização das letras de crédito e discute as correspondentes medidas de prevenção de risco.
Com base numa abordagem qualitativa, foi possível obter uma perspetiva prática sobre os
riscos e as correspondentes medidas de prevenção de risco. Os resultados deste estudo
exploratório sugerem que existe um consenso em considerar o princípio da independência da
carta de crédito como uma das suas principais fontes de risco. Esse consenso sugere que o
desenvolvimento futuro da letra de crédito deverá passar por reduzir a sua independência, mas
sem perder completamente a sua essência de independência. A evolução também deverá
incluir o desenvolvimento cooperativo das operações e o uso das plataformas digitais para
facilitar a investigação da credibilidade dos parceiros de negócios
Walking, Weak first-order transitions, and Complex CFTs
We discuss walking behavior in gauge theories and weak first-order phase
transitions in statistical physics. Despite appearing in very different systems
(QCD below the conformal window, the Potts model, deconfined criticality) these
two phenomena both imply approximate scale invariance in a range of energies
and have the same RG interpretation: a flow passing between pairs of fixed
point at complex coupling. We discuss what distinguishes a real theory from a
complex theory and call these fixed points complex CFTs. By using conformal
perturbation theory we show how observables of the walking theory are
computable by perturbing the complex CFTs. This paper discusses the general
mechanism while a companion paper [1] will treat a specific and computable
example: the two-dimensional Q-state Potts model with Q > 4. Concerning walking
in 4d gauge theories, we also comment on the (un)likelihood of the light
pseudo-dilaton, and on non-minimal scenarios of the conformal window
termination.Comment: 38 pages, added reference
Non-gaussianity of the critical 3d Ising model
We discuss the 4pt function of the critical 3d Ising model, extracted from
recent conformal bootstrap results. We focus on the non-gaussianity Q - the
ratio of the 4pt function to its gaussian part given by three Wick
contractions. This ratio reveals significant non-gaussianity of the critical
fluctuations. The bootstrap results are consistent with a rigorous inequality
due to Lebowitz and Aizenman, which limits Q to lie between 1/3 and 1.Comment: 10 pages, 6 figures; v2: refs added; v3: refs updated, published
version; v4: acknowledgement adde
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