{"title":"A robust stochastic control problem with applications to monotone mean-variance problems","authors":"Yuyang Chen, Tianjiao Hua, Peng Luo","doi":"arxiv-2408.08595","DOIUrl":"https://doi.org/arxiv-2408.08595","url":null,"abstract":"This paper studies a robust stochastic control problem with a monotone\u0000mean-variance cost functional and random coefficients. The main technique is to\u0000find the saddle point through two backward stochastic differential equations\u0000(BSDEs) with unbounded coefficients. We further show that the robust stochastic\u0000control problem shares the same optimal control and optimal value with the\u0000stochastic control problem with a mean-variance cost functional. The results\u0000obtained are then applied to monotone mean-variance and mean-variance portfolio\u0000selection problems and monotone mean-variance and mean-variance\u0000investment-reinsurance problems.","PeriodicalId":501084,"journal":{"name":"arXiv - QuantFin - Mathematical Finance","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142216349","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The mean-variance portfolio selection based on the average and current profitability of the risky asset","authors":"Yu Li, Yuhan Wu, Shuhua Zhang","doi":"arxiv-2408.07969","DOIUrl":"https://doi.org/arxiv-2408.07969","url":null,"abstract":"We study the continuous-time pre-commitment mean-variance portfolio selection\u0000in a time-varying financial market. By introducing two indexes which\u0000respectively express the average profitability of the risky asset (AP) and the\u0000current profitability of the risky asset (CP), the optimal portfolio selection\u0000is represented by AP and CP. Furthermore, instead of the traditional maximum\u0000likelihood estimation (MLE) of return rate and volatility of the risky asset,\u0000we estimate AP and CP with the second-order variation of an auxiliary wealth\u0000process. We prove that the estimations of AP and CP in this paper are more\u0000accurate than that in MLE. And, the portfolio selection is implemented in\u0000various simulated and real financial markets. Numerical studies confirm the\u0000superior performance of our portfolio selection with the estimation of AP and\u0000CP under various evaluation criteria.","PeriodicalId":501084,"journal":{"name":"arXiv - QuantFin - Mathematical Finance","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142216344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Endogenous Crashes as Phase Transitions","authors":"Revant Nayar, Minhajul Islam","doi":"arxiv-2408.06433","DOIUrl":"https://doi.org/arxiv-2408.06433","url":null,"abstract":"This paper explores the mechanisms behind extreme financial events,\u0000specifically market crashes, by employing the theoretical framework of phase\u0000transitions. We focus on endogenous crashes, driven by internal market\u0000dynamics, and model these events as first-order phase transitions critical,\u0000stochastic, and dynamic. Through a comparative analysis of early warning\u0000signals associated with each type of transition, we demonstrate that dynamic\u0000phase transitions (DPT) offer a more accurate representation of market crashes\u0000than critical (CPT) or stochastic phase transitions (SPT). Unlike existing\u0000models, such as the Log-Periodic Power Law (LPPL) model, which often suffers\u0000from overfitting and false positives, our approach grounded in DPT provides a\u0000more robust prediction framework. Empirical findings, based on an analysis of\u0000S&P 500 stocks from 2019 to 2024, reveal significant trends in volatility and\u0000anomalous dimensions before crashes, supporting the superiority of the DPT\u0000model. This work contributes to a deeper understanding of the predictive\u0000signals preceding market crashes and offers a novel perspective on their\u0000underlying dynamics.","PeriodicalId":501084,"journal":{"name":"arXiv - QuantFin - Mathematical Finance","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142216347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Linear reflected backward stochastic differential equations arising from vulnerable claims in markets with random horizon","authors":"T. Choulli, S. Alsheyab","doi":"arxiv-2408.04758","DOIUrl":"https://doi.org/arxiv-2408.04758","url":null,"abstract":"This paper considers the setting governed by $(mathbb{F},tau)$, where\u0000$mathbb{F}$ is the \"public\" flow of information, and $tau$ is a random time\u0000which might not be $mathbb{F}$-observable. This framework covers credit risk\u0000theory and life insurance. In this setting, we assume $mathbb{F}$ being\u0000generated by a Brownian motion $W$ and consider a vulnerable claim $xi$, whose\u0000payment's policy depends {it{essentially}} on the occurrence of $tau$. The\u0000hedging problems, in many directions, for this claim led to the question of\u0000studying the linear reflected-backward-stochastic differential equations (RBSDE\u0000hereafter), begin{equation*} begin{split}\u0000&dY_t=f(t)d(twedgetau)+Z_tdW_{twedge{tau}}+dM_t-dK_t,quad Y_{tau}=xi,\u0000& Ygeq Squadmbox{on}quad Lbrack0,tauLbrack,quad\u0000displaystyleint_0^{tau}(Y_{s-}-S_{s-})dK_s=0quad Pmbox{-a.s.}.end{split}\u0000end{equation*} This is the objective of this paper. For this RBSDE and without\u0000any further assumption on $tau$ that might neglect any risk intrinsic to its\u0000stochasticity, we answer the following: a) What are the sufficient minimal\u0000conditions on the data $(f, xi, S, tau)$ that guarantee the existence of the\u0000solution to this RBSDE? b) How can we estimate the solution in norm using $(f,\u0000xi, S)$? c) Is there an $mathbb F$-RBSDE that is intimately related to the\u0000current one and how their solutions are related to each other? This latter\u0000question has practical and theoretical leitmotivs.","PeriodicalId":501084,"journal":{"name":"arXiv - QuantFin - Mathematical Finance","volume":"65 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141947294","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Efficient simulation of the SABR model","authors":"Jaehyuk Choi, Lilian Hu, Yue Kuen Kwok","doi":"arxiv-2408.01898","DOIUrl":"https://doi.org/arxiv-2408.01898","url":null,"abstract":"We propose an efficient and reliable simulation scheme for the\u0000stochastic-alpha-beta-rho (SABR) model. The two challenges of the SABR\u0000simulation lie in sampling (i) the integrated variance conditional on terminal\u0000volatility and (ii) the terminal price conditional on terminal volatility and\u0000integrated variance. For the first sampling procedure, we analytically derive\u0000the first four moments of the conditional average variance, and sample it from\u0000the moment-matched shifted lognormal approximation. For the second sampling\u0000procedure, we approximate the conditional terminal price as a\u0000constant-elasticity-of-variance (CEV) distribution. Our CEV approximation\u0000preserves the martingale condition and precludes arbitrage, which is a key\u0000advantage over Islah's approximation used in most SABR simulation schemes in\u0000the literature. Then, we adopt the exact sampling method of the CEV\u0000distribution based on the shifted-Poisson-mixture Gamma random variable. Our\u0000enhanced procedures avoid the tedious Laplace inversion algorithm for sampling\u0000integrated variance and non-efficient inverse transform sampling of the forward\u0000price in some of the earlier simulation schemes. Numerical results demonstrate\u0000our simulation scheme to be highly efficient, accurate, and reliable.","PeriodicalId":501084,"journal":{"name":"arXiv - QuantFin - Mathematical Finance","volume":"50 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141947296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A Path Integral Approach for Time-Dependent Hamiltonians with Applications to Derivatives Pricing","authors":"Mark Stedman, Luca Capriotti","doi":"arxiv-2408.02064","DOIUrl":"https://doi.org/arxiv-2408.02064","url":null,"abstract":"We generalize a semi-classical path integral approach originally introduced\u0000by Giachetti and Tognetti [Phys. Rev. Lett. 55, 912 (1985)] and Feynman and\u0000Kleinert [Phys. Rev. A 34, 5080 (1986)] to time-dependent Hamiltonians, thus\u0000extending the scope of the method to the pricing of financial derivatives. We\u0000illustrate the accuracy of the approach by presenting results for the\u0000well-known, but analytically intractable, Black-Karasinski model for the\u0000dynamics of interest rates. The accuracy and computational efficiency of this\u0000path integral approach makes it a viable alternative to fully-numerical schemes\u0000for a variety of applications in derivatives pricing.","PeriodicalId":501084,"journal":{"name":"arXiv - QuantFin - Mathematical Finance","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141947295","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The indifference value of the weak information","authors":"Fabrice Baudoin, Oleksii Mostovyi","doi":"arxiv-2408.02137","DOIUrl":"https://doi.org/arxiv-2408.02137","url":null,"abstract":"We propose indifference pricing to estimate the value of the weak\u0000information. Our framework allows for tractability, quantifying the amount of\u0000additional information, and permits the description of the smallness and the\u0000stability with respect to small perturbations of the weak information. We\u0000provide sharp conditions for the stability with counterexamples. The results\u0000rely on a theorem of independent interest on the stability of the optimal\u0000investment problem with respect to small changes in the physical probability\u0000measure. We also investigate contingent claims that are indifference price\u0000invariant with respect to changes in weak information. We show that, in\u0000incomplete models, the class of information-invariant claims includes the\u0000replicable claims, and it can be strictly bigger. In particular, in complete\u0000models, all contingent claims are information invariant. We augment the results\u0000with examples and counterexamples.","PeriodicalId":501084,"journal":{"name":"arXiv - QuantFin - Mathematical Finance","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141969627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Generative model for financial time series trained with MMD using a signature kernel","authors":"Lu Chung I, Julian Sester","doi":"arxiv-2407.19848","DOIUrl":"https://doi.org/arxiv-2407.19848","url":null,"abstract":"Generating synthetic financial time series data that accurately reflects\u0000real-world market dynamics holds tremendous potential for various applications,\u0000including portfolio optimization, risk management, and large scale machine\u0000learning. We present an approach for training generative models for financial\u0000time series using the maximum mean discrepancy (MMD) with a signature kernel.\u0000Our method leverages the expressive power of the signature transform to capture\u0000the complex dependencies and temporal structures inherent in financial data. We\u0000employ a moving average model to model the variance of the noise input,\u0000enhancing the model's ability to reproduce stylized facts such as volatility\u0000clustering. Through empirical experiments on S&P 500 index data, we demonstrate\u0000that our model effectively captures key characteristics of financial time\u0000series and outperforms a comparable GAN-based approach. In addition, we explore\u0000the application of the synthetic data generated to train a reinforcement\u0000learning agent for portfolio management, achieving promising results. Finally,\u0000we propose a method to add robustness to the generative model by tweaking the\u0000noise input so that the generated sequences can be adjusted to different market\u0000environments with minimal data.","PeriodicalId":501084,"journal":{"name":"arXiv - QuantFin - Mathematical Finance","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141863627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Consumption-investment optimization with Epstein-Zin utility in unbounded non-Markovian markets","authors":"Zixin Feng, Dejian Tian, Harry Zheng","doi":"arxiv-2407.19995","DOIUrl":"https://doi.org/arxiv-2407.19995","url":null,"abstract":"The paper investigates the consumption-investment problem for an investor\u0000with Epstein-Zin utility in an incomplete market. A non-Markovian environment\u0000with unbounded parameters is considered, which is more realistic in practical\u0000financial scenarios compared to the Markovian setting. The optimal consumption\u0000and investment strategies are derived using the martingale optimal principle\u0000and quadratic backward stochastic differential equations (BSDEs) whose\u0000solutions admit some exponential moment. This integrability property plays a\u0000crucial role in establishing a key martingale argument. In addition, the paper\u0000also examines the associated dual problem and several models within the\u0000specified parameter framework.","PeriodicalId":501084,"journal":{"name":"arXiv - QuantFin - Mathematical Finance","volume":"191 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141863626","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Julio Backhoff-Veraguas, Gudmund Pammer, Walter Schachermayer
{"title":"The Gradient Flow of the Bass Functional in Martingale Optimal Transport","authors":"Julio Backhoff-Veraguas, Gudmund Pammer, Walter Schachermayer","doi":"arxiv-2407.18781","DOIUrl":"https://doi.org/arxiv-2407.18781","url":null,"abstract":"Given $mu$ and $nu$, probability measures on $mathbb R^d$ in convex order,\u0000a Bass martingale is arguably the most natural martingale starting with law\u0000$mu$ and finishing with law $nu$. Indeed, this martingale is obtained by\u0000stretching a reference Brownian motion so as to meet the data $mu,nu$. Unless\u0000$mu$ is a Dirac, the existence of a Bass martingale is a delicate subject,\u0000since for instance the reference Brownian motion must be allowed to have a\u0000non-trivial initial distribution $alpha$, not known in advance. Thus the key\u0000to obtaining the Bass martingale, theoretically as well as practically, lies in\u0000finding $alpha$. In cite{BaSchTsch23} it has been shown that $alpha$ is determined as the\u0000minimizer of the so-called Bass functional. In the present paper we propose to\u0000minimize this functional by following its gradient flow, or more precisely, the\u0000gradient flow of its $L^2$-lift. In our main result we show that this gradient\u0000flow converges in norm to a minimizer of the Bass functional, and when $d=1$ we\u0000further establish that convergence is exponentially fast.","PeriodicalId":501084,"journal":{"name":"arXiv - QuantFin - Mathematical Finance","volume":"74 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141863628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}