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## Market bubbles and crashes

Kaizoji, T.; Sornette, D.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
57.91478%
Episodes of market crashes have fascinated economists for centuries. Although many academics, practitioners and policy makers have studied questions related to collapsing asset price bubbles, there is little consensus yet about their causes and effects. This review and essay evaluates some of the hypotheses offered to explain the market crashes that often follow asset price bubbles. Starting from historical accounts and syntheses of past bubbles and crashes, we put the problem in perspective with respect to the development of the efficient market hypothesis. We then present the models based on heterogeneous agents and the limits to arbitrage that prevent rational agents from bursting bubbles before they inflate. Then, we explore another set of explanations of why rational traders would be led to actually profit from and surf on bubbles, by anticipating the behavior of noise traders or by realizing the difficulties in synchronizing their actions. We then end by discussing a complex system approach of social imitation leading to collective market regimes like herding and the phenomenon of bifurcation (or phase transition) that rationalize what crash can occur in unstable market regimes. The key insight is that diagnosing bubbles may be feasible when taking into account the positive feedback mechanisms that give rise to transient "super-exponential" price growth...

## Bank Networks from Text: Interrelations, Centrality and Determinants

Rönnqvist, Samuel; Sarlin, Peter
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
57.91478%
In the wake of the still ongoing global financial crisis, bank interdependencies have come into focus in trying to assess linkages among banks and systemic risk. To date, such analysis has largely been based on numerical data. By contrast, this study attempts to gain further insight into bank interconnections by tapping into financial discourse. We present a text-to-network process, which has its basis in co-occurrences of bank names and can be analyzed quantitatively and visualized. To quantify bank importance, we propose an information centrality measure to rank and assess trends of bank centrality in discussion. For qualitative assessment of bank networks, we put forward a visual, interactive interface for better illustrating network structures. We illustrate the text-based approach on European Large and Complex Banking Groups (LCBGs) during the ongoing financial crisis by quantifying bank interrelations and centrality from discussion in 3M news articles, spanning 2007Q1 to 2014Q3.; Comment: Quantitative Finance, forthcoming in 2015

## The Zeeman Effect in Finance: Libor Spectroscopy and Basis Risk Management

Bianchetti, Marco
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
58.007603%
Once upon a time there was a classical financial world in which all the Libors were equal. Standard textbooks taught that simple relations held, such that, for example, a 6 months Libor Deposit was replicable with a 3 months Libor Deposits plus a 3x6 months Forward Rate Agreement (FRA), and that Libor was a good proxy of the risk free rate required as basic building block of no-arbitrage pricing theory. Nowadays, in the modern financial world after the credit crunch, some Libors are more equal than others, depending on their rate tenor, and classical formulas are history. Banks are not anymore too "big to fail", Libors are fixed by panels of risky banks, and they are risky rates themselves. These simple empirical facts carry very important consequences in derivative's trading and risk management, such as, for example, basis risk, collateralization and regulatory pressure in favour of Central Counterparties. Something that should be carefully considered by anyone managing even a single plain vanilla Swap. In this qualitative note we review the problem trying to shed some light on this modern animal farm, recurring to an analogy with quantum physics, the Zeeman effect.

## On the new central bank strategy toward monetary and financial instabilities management in finances: Econophysical analysis of nonlinear dynamical financial systems

Ledenyov, Dimitri O.; Ledenyov, Viktor O.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
58.29627%
We describe the innovations in finances, introduced over the recent decades, and analyze most of the business and regulatory challenges, faced by the financial industry, because of the present disruptive changes in the global capital markets. We use the integrative thinking approach to formulate the new central bank strategy and propose that the new strategy has to be focused on the constant management of the monetary and financial instabilities, using the knowledge base in the field of econophysics. We propose the new theoretical model of economics, which is called the Nonlinear Dynamic Stochastic General Equilibrium (NDSGE), which takes to the account the nonlinearities, appearing during the interaction between the business cycles. We show that the central banks, which will apply the knowledge gained from the econophysical analysis to understand the complex processes in the national financial systems in the time of high volatility in global capital markets, will be able to govern the national financial systems successfully.; Comment: 8 pages, 1 table

## A unified approach to pricing and risk management of equity and credit risk

Fontana, Claudio; Montes, Juan Miguel A.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
57.840537%
We propose a unified framework for equity and credit risk modeling, where the default time is a doubly stochastic random time with intensity driven by an underlying affine factor process. This approach allows for flexible interactions between the defaultable stock price, its stochastic volatility and the default intensity, while maintaining full analytical tractability. We characterise all risk-neutral measures which preserve the affine structure of the model and show that risk management as well as pricing problems can be dealt with efficiently by shifting to suitable survival measures. As an example, we consider a jump-to-default extension of the Heston stochastic volatility model.; Comment: 18 pages, 4 figures. Revised version (remarks and references added)

## A General Duality Relation with Applications in Quantitative Risk Management

Hauser, Raphael; Shahverdyan, Sergey; Embrechts, Paul
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
57.58757%
A fundamental problem in risk management is the robust aggregation of different sources of risk in a situation where little or no data are available to infer information about their dependencies. A popular approach to solving this problem is to formulate an optimization problem under which one maximizes a risk measure over all multivariate distributions that are consistent with the available data. In several special cases of such models, there exist dual problems that are easier to solve or approximate, yielding robust bounds on the aggregated risk. In this chapter we formulate a general optimization problem, which can be seen as a doubly infinite linear programming problem, and we show that the associated dual generalizes several well known special cases and extends to new risk management models we propose.

## Price Impact

Bouchaud, J. P.; Management, Capital Fund
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
57.91478%
We define what "Price Impact" means, and how it is measured and modelled in the recent literature. Although this notion seems to convey the idea of a forceful and intuitive mechanism, we discuss why things might not be that simple. Empirical studies show that while the correlation between signed order flow and price changes is strong, the impact of trades on prices is neither linear in volume nor permanent. Impact allows private information to be reflected in prices, but by the same token, random fluctuations in order flow must also contribute to the volatility of markets.; Comment: Entry for the upcoming "Encyclopedia of Quantitative Finance"

## The t copula with Multiple Parameters of Degrees of Freedom: Bivariate Characteristics and Application to Risk Management

Luo, Xiaolin; Shevchenko, Pavel V.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
58.07357%
The t copula is often used in risk management as it allows for modelling tail dependence between risks and it is simple to simulate and calibrate. However, the use of a standard t copula is often criticized due to its restriction of having a single parameter for the degrees of freedom (dof) that may limit its capability to model the tail dependence structure in a multivariate case. To overcome this problem, grouped t copula was proposed recently, where risks are grouped a priori in such a way that each group has a standard t copula with its specific dof parameter. In this paper we propose the use of a grouped t copula, where each group consists of one risk factor only, so that a priori grouping is not required. The copula characteristics in the bivariate case are studied. We explain simulation and calibration procedures, including a simulation study on finite sample properties of the maximum likelihood estimators and Kendall's tau approximation. This new copula can be significantly different from the standard t copula in terms of risk measures such as tail dependence, value at risk and expected shortfall. Keywords: grouped t copula, tail dependence, risk management.

## Contraction or steady state? An analysis of credit risk management in Italy in the period 2008-2012

Olgiati, Stefano; Danovi, Alessandro
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
57.44266%
Credit risk management in Italy is characterized, in the period June 2008 to June 2012, by frequent (frequency=0.5 cycles per year) and intense (peak amplitude: mean=39.2 billion Euros, s.e.=2.83 billion Euros) quarterly contractions and expansions around the mean (915.4 billion Euros, s.e.=3.59 billion Euros) of the nominal total credit used by non-financial corporations. Such frequent and intense fluctuations are frequently ascribed to exogenous Basel II procyclical effects on credit flow into the economy and, consequently, Basel III output based point in time Credit to GDP countercyclical buffering advocated. We have tested the opposite null hypotheses that such variation is significantly correlated to actual default rates, and that such correlation is explained by fluctuations of credit supply around a steady state. We have found that, in the period June 2008 to June 2012 (n=17), linear regression of credit growth rates on default rates reveals a negative correlation of r=minus 0.6903 with R squared=0.4765, and that credit supply fluctuates steadily around the default rate with an Internal Steady State Parameter SSP=0.00245 with chi squared=37.47 (v=16, P<.005). We conclude that fluctuations of the total credit used by non-financial corporations are exhaustively explained by variation of the independent variable default rate...

## On Game-Theoretic Risk Management (Part Two) - Algorithms to Compute Nash-Equilibria in Games with Distributions as Payoffs

Rass, Stefan
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
57.840537%
The game-theoretic risk management framework put forth in the precursor work "Towards a Theory of Games with Payoffs that are Probability-Distributions" (arXiv:1506.07368 [q-fin.EC]) is herein extended by algorithmic details on how to compute equilibria in games where the payoffs are probability distributions. Our approach is "data driven" in the sense that we assume empirical data (measurements, simulation, etc.) to be available that can be compiled into distribution models, which are suitable for efficient decisions about preferences, and setting up and solving games using these as payoffs. While preferences among distributions turn out to be quite simple if nonparametric methods (kernel density estimates) are used, computing Nash-equilibria in games using such models is discovered as inefficient (if not impossible). In fact, we give a counterexample in which fictitious play fails to converge for the (specifically unfortunate) choice of payoff distributions in the game, and introduce a suitable tail approximation of the payoff densities to tackle the issue. The overall procedure is essentially a modified version of fictitious play, and is herein described for standard and multicriteria games, to iteratively deliver an (approximate) Nash-equilibrium.

## On the Risk Management with Application of Econophysics Analysis in Central Banks and Financial Institutions

Ledenyov, Dimitri O.; Ledenyov, Viktor O.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
58.362236%
The purpose of this research article is to discover how the econophysics analysis can complement the econometrics models in application to the risk management in the central banks and financial institutions, operating within the nonlinear dynamical financial system. We consider the modern risk management models and show the appropriate techniques to calculate the various existing risks in the finances. We make a few comments on the possible limitations in the models of statistical modeling of volatility such as the Autoregressive Conditional Heteroskedasticity (GARCH) model, because of the nonlinearities appearance in the nonlinear dynamical financial systems. We propose that the various types of nonlinearities, which can originate in the financial and economical systems, have to be taken to the detailed consideration during the Cost of Capital calculation in the finances and economics. We propose the new theory of nonlinear dynamic volatilities and the new nonlinear dynamic chaos (NDC) volatility model for the statistical modeling of financial volatility with the aim to determine the Value at Risk.; Comment: 10 pages

## Theoretical Sensitivity Analysis for Quantitative Operational Risk Management

Kato, Takashi
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
77.63782%
We study the asymptotic behavior of the difference between the values at risk VaR(L) and VaR(L+S) for heavy tailed random variables L and S for application in sensitivity analysis of quantitative operational risk management within the framework of the advanced measurement approach of Basel II (and III). Here L describes the loss amount of the present risk profile and S describes the loss amount caused by an additional loss factor. We obtain different types of results according to the relative magnitudes of the thicknesses of the tails of L and S. In particular, if the tail of S is sufficiently thinner than the tail of L, then the difference between prior and posterior risk amounts VaR(L+S) - VaR(L) is asymptotically equivalent to the expectation (expected loss) of S.; Comment: 19 pages, 1 figure, 4 tables

## An initial approach to Risk Management of Funding Costs

Brigo, Damiano; Durand, Cyril
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
57.3657%
In this note we sketch an initial tentative approach to funding costs analysis and management for contracts with bilateral counterparty risk in a simplified setting. We depart from the existing literature by analyzing the issue of funding costs and benefits under the assumption that the associated risks cannot be hedged properly. We also model the treasury funding spread by means of a stochastic Weighted Cost of Funding Spread (WCFS) which helps describing more realistic financing policies of a financial institution. We elaborate on some limitations in replication-based Funding / Credit Valuation Adjustments we worked on ourselves in the past, namely CVA, DVA, FVA and related quantities as generally discussed in the industry. We advocate as a different possibility, when replication is not possible, the analysis of the funding profit and loss distribution and explain how long term funding spreads, wrong way risk and systemic risk are generally overlooked in most of the current literature on risk measurement of funding costs. As a matter of initial illustration, we discuss in detail the funding management of interest rate swaps with bilateral counterparty risk in the simplified setup of our framework through numerical examples and via a few simplified assumptions.

## A new approach for scenario generation in Risk management

Ortega, Juan-Pablo; Pullirsch, Rainer; Teichmann, Josef; Wergieluk, Julian
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
58.176377%
We provide a new dynamic approach to scenario generation for the purposes of risk management in the banking industry. We connect ideas from conventional techniques -- like historical and Monte Carlo simulation -- and we come up with a hybrid method that shares the advantages of standard procedures but eliminates several of their drawbacks. Instead of considering the static problem of constructing one or ten day ahead distributions for vectors of risk factors, we embed the problem into a dynamic framework, where any time horizon can be consistently simulated. Additionally, we use standard models from mathematical finance for each risk factor, whence bridging the worlds of trading and risk management. Our approach is based on stochastic differential equations (SDEs), like the HJM-equation or the Black-Scholes equation, governing the time evolution of risk factors, on an empirical calibration method to the market for the chosen SDEs, and on an Euler scheme (or high-order schemes) for the numerical evaluation of the respective SDEs. The empirical calibration procedure presented in this paper can be seen as the SDE-counterpart of the so called Filtered Historical Simulation method; the behavior of volatility stems in our case out of the assumptions on the underlying SDEs. Furthermore...

## Credit contagion and risk management with multiple non-ordered defaults

Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
58.007603%
The classical reduced-form and filtration expansion framework in credit risk is extended to the case of multiple, non-ordered defaults, assuming that conditional densities of the default times exist. Intensities and pricing formulas are derived, revealing how information driven default contagion arises in these models. We then analyze the impact of ordering the default times before expanding the filtration. While not important for pricing, the effect is significant in the context of risk management, and becomes even more pronounced for highly correlated and asymmetrically distributed defaults. Finally, we provide a general scheme for constructing and simulating the default times, given that a model for the conditional densities has been chosen.; Comment: This paper has been withdrawn by the authors because some of the main results have significant overlap with others available in the literature

## New copulas based on general partitions-of-unity and their applications to risk management

Pfeifer, Dietmar; Tsatedem, Hervé Awoumlac; Mändle, Andreas; Girschig, Côme
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
57.5216%
We construct new multivariate copulas on the basis of a generalized infinite partition-of-unity approach. This approach allows - in contrast to finite partition-of-unity copulas - for tail-dependence as well as for asymmetry. A possibility of fitting such copulas to real data from quantitative risk management is also pointed out.; Comment: 22 pages

## Pricing and Risk Management with High-Dimensional Quasi Monte Carlo and Global Sensitivity Analysis

Bianchetti, Marco; Kucherenko, Sergei; Scoleri, Stefano
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
58.292593%
We review and apply Quasi Monte Carlo (QMC) and Global Sensitivity Analysis (GSA) techniques to pricing and risk management (greeks) of representative financial instruments of increasing complexity. We compare QMC vs standard Monte Carlo (MC) results in great detail, using high-dimensional Sobol' low discrepancy sequences, different discretization methods, and specific analyses of convergence, performance, speed up, stability, and error optimization for finite differences greeks. We find that our QMC outperforms MC in most cases, including the highest-dimensional simulations and greeks calculations, showing faster and more stable convergence to exact or almost exact results. Using GSA, we are able to fully explain our findings in terms of reduced effective dimension of our QMC simulation, allowed in most cases, but not always, by Brownian bridge discretization. We conclude that, beyond pricing, QMC is a very promising technique also for computing risk figures, greeks in particular, as it allows to reduce the computational effort of high-dimensional Monte Carlo simulations typical of modern risk management.; Comment: 43 pages, 21 figures, 6 tables

## Fractional smoothness and applications in finance

Geiss, Stefan; Gobet, Emmanuel
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
57.47388%
This overview article concerns the notion of fractional smoothness of random variables of the form $g(X_T)$, where $X=(X_t)_{t\in [0,T]}$ is a certain diffusion process. We review the connection to the real interpolation theory, give examples and applications of this concept. The applications in stochastic finance mainly concern the analysis of discrete time hedging errors. We close the review by indicating some further developments.; Comment: Chapter of AMAMEF book. 20 pages.

## A Non-Gaussian Approach to Risk Measures

Bormetti, G.; Cisana, E.; Montagna, G.; Nicrosini, O.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
57.840537%
Reliable calculations of financial risk require that the fat-tailed nature of prices changes is included in risk measures. To this end, a non-Gaussian approach to financial risk management is presented, modeling the power-law tails of the returns distribution in terms of a Student-t distribution. Non-Gaussian closed-form solutions for Value-at-Risk and Expected Shortfall are obtained and standard formulae known in the literature under the normality assumption are recovered as a special case. The implications of the approach for risk management are demonstrated through an empirical analysis of financial time series from the Italian stock market and in comparison with the results of the most widely used procedures of quantitative finance. Particular attention is paid to quantify the size of the errors affecting the market risk measures obtained according to different methodologies, by employing a bootstrap technique.; Comment: Latex 15 pages, 3 figures and 5 tables 68% c. levels for tail exponents corrected, conclusions unchanged

## Four Points Beginner Risk Managers Should Learn from Jeff Holman's Mistakes in the Discussion of Antifragile

Taleb, Nassim Nicholas