Defines risk-free portfolios and risk-free rate using gauge symmetries.
problem Identifying a consistent definition of risk-free rate in economics.
method Introduces three gauge invariant differential operators to define risk-free portfolios and identifies the risk-free rate as the return of an infinitely diversified portfolio.
result Identifies the risk-free rate as the return of an infinitely diversified portfolio and connects it to global price rescaling as a gauge symmetry.
Paper proposes a robust Sharpe ratio portfolio method.
problem Comparing portfolios with unknown risk-free asset.
method Cross-efficiency evaluation to maximize Sharpe ratio.
result Explicit expression for robust Sharpe ratio portfolio.
Investigates optimal portfolios with risk-free assets, minimizing investment risk.
problem Investment risk minimization with budget and return constraints.
method Replica analysis and exploration of implications of a risk-free asset.
result Implications of a risk-free asset on optimal portfolio and investment risk.
The paper simplifies hedging and portfolio allocation in markets without a risk-free asset.
problem Optimal hedging and portfolio allocation in markets without a risk-free asset.
method Establishes equivalence between hedging with and without numeraire change, uses oblique projections.
result Explicit expressions for optimal strategies and efficient frontier computation.
Traders underestimated risk-free rates, leading to poor investments.
problem Incorrect setting of risk-free rates by traders.
method Analysis of investment decisions and financial models.
result Underestimating risk-free rates led to flawed investment decisions.
This paper revisits mean-variance portfolio theory, addressing limitations in diversification models.
problem Current diversification models assume exchangeable asset returns and ignore risk-free assets.
method Analyzes diversification under full information about asset returns and risk, considering both risky and risk-free assets.
result The conventional wisdom of mean-variance portfolio theory is not universally valid, especially when asset returns are not exchangeable.
We consider the mean--variance portfolio optimization problem under the game theoretic framework and without risk-free assets. The problem is solved semi-explicitly by applying the extended Hamilton--Jacobi--Bellman equation. Although the coefficient of risk aversion in our model is a constant, the optimal amounts of m…
Investigates optimal investment strategies under CPT with risk-free and risky assets over multiple periods.
problem Optimal portfolio selection under CPT with constraints and stochastic benchmark.
method Numerical analysis of optimal CPT-investment strategies sensitivity to model parameters.
result Investment strategies under CPT are sensitive to model parameters.
Machine learning improves portfolio allocation between index and risk-free assets.
problem Finding optimal portfolio rules for time-varying returns and volatility.
method Two Random Forest models: one for sign probabilities of excess return, the other for optimized volatility.
result Substantial improvements in utility, risk-adjusted returns, and maximum drawdowns over buy-and-hold.
Analyzes various methods to compare portfolio performance, explaining why simple choices can outperform sophisticated ones.
problem Explains why simple portfolio choices can outperform more complex ones.
method Examines several comparison criteria for portfolios, including those on the market line and in the absence of a risk-free asset.
result Clarifies why some portfolios may seem to outperform others, providing theoretical insights.
We consider the problem of finding the efficient frontier associated with the risk-return portfolio optimization model. We derive the analytical expression of the efficient frontier for a portfolio of N risky assets, and for the case when a risk-free asset is added to the model. Also, we provide an R implementation, an…
Investors only hold risk-free assets if certain conditions are met.
problem Investment behavior under multiprior minimax utility maximization.
method Continuous-time financial market analysis with semimartingales.
result Portfolio consists only of risk-free asset if specific conditions on priors are met.
This paper derives a portfolio decomposition formula when the agent maximizes utility of her wealth at some finite planning horizon. The financial market is complete and consists of multiple risky assets (stocks) plus a risk free asset. The stocks are modelled as exponential Brownian motions with drift and volatility b…
Solves portfolio optimization with costs using numerical methods.
problem Dynamic portfolio optimization with transaction costs and constraints.
method Numerical dynamic programming techniques.
result Problems can now be solved tractably.
We investigate the use of Kelly's strategy in the construction of an optimal portfolio of assets. For lognormally distributed asset returns, we derive approximate analytical results for the optimal investment fractions in various settings. We show that when mean returns and volatilities of the assets are small and ther…
It is well established that in a market with inclusion of a risk-free asset the single-period mean-variance efficient frontier is a straight line tangent to the risky region, a fact that is the very foundation of the classical CAPM. In this paper, it is shown that in a continuous-time market where the risky prices are …
The paper integrates behavioral distortions into portfolio optimization using implied probability weighting functions.
problem Behavioral distortions in probability weighting affect portfolio optimization under different return distributions.
method Developed a unified framework to extract probability weighting functions from optimal portfolios modeled under Gaussian and NIG distributions.
result Increasing tail fatness amplifies behavioral distortions, and shifts in risk-free rates alter the curvature of these distortions.
Investor optimizes portfolio to manage risk with heavy-tailed stock returns.
problem Managing risk in portfolios with heavy-tailed stock returns.
method Markov Decision Process and dynamic programming for optimal strategies and value function.
result Optimal strategies and value function maximizing expected utility for both parametric and non-parametric distributions.
The paper identifies inconsistencies in post-crisis derivative pricing methods and derives no-arbitrage expressions.
problem Inconsistencies in post-crisis derivative pricing methods, particularly regarding cost components to a risk-free money account.
method Derives no-arbitrage expressions for default-risky derivative contracts with and without collateral.
result Avoids inconsistencies in derivative pricing methods by deriving no-arbitrage expressions.
This study compares Markowitz and Single-Index models for Malaysian stocks.
problem Optimizing portfolio selection for Malaysian stocks using different models.
method Applied Markowitz and Single-Index models to 10-year historical data of 10 stocks and a risk-free asset.
result Comparison of minimum variance and maximum Sharpe portfolios for both models under various constraints.
This paper tackles cost-sensitive portfolio optimization under ambiguous return distributions.
problem Tackles cost-sensitive distributionally robust log-optimal portfolio problem with ambiguous return distributions.
method Uses Wasserstein metric for distributional ambiguity, incorporates convex transaction costs, and approximates infinite-dimensional problem with finite convex program.
result Establishes conditions for robustly survivable trades and validates theoretical framework with empirical studies.
What are the prices of random variables? In this paper, we define the least-squares prices of coin-flipping games, which are proved to be minimal, positive linear, and arbitrage-free. These prices depend both on a set of games that are available for investing simultaneously and on a risk-free interest rate. In addition…
Investment strategy using fractional Kelly portfolios for better growth expectations.
problem Understanding optimal growth strategies for investors with varying risk appetites.
method Developed a mathematical framework for fractional-Kelly portfolios, analyzing Sharpe ratios and log-returns.
result Fractional Kelly portfolios provide a simple distributional relationship between Sharpe ratio, fractional coefficient, and log-returns.
Flow taxes and stock taxes preserve portfolio neutrality under specific conditions.
problem Analyzing the impact of different types of taxes on portfolio choice.
method Extending the neutrality result to a full system of ownership taxes, showing how each tax modifies the drift of the wealth process.
result The combined system of taxes preserves portfolio neutrality under three conditions, and the drift-shift symmetry generalizes to a drift-shift-and-rescale symmetry.
We consider a portfolio with call option and the corresponding underlying asset under the standard assumption that stock-market price represents a random variable with lognormal distribution. Minimizing the variance (hedging risk) of the portfolio on the date of maturity of the call option we find a fraction of the ass…
Investor optimizes portfolio under VaR constraint with heavy-tailed stock returns.
problem Managing Value at Risk (VaR) for portfolios with heavy-tailed stock price returns.
method Formulated a dynamic optimisation problem using stochastic maximum principle, approximating the value function and optimal strategy without explicit solutions.
result Close concordance with financial intuition, providing insights for high-frequency traders.
Paper solves portfolio optimization with fuzzy risk and credibility theory.
problem Optimizing investment in risky assets with fuzzy risk and credibility theory.
method Formulated as an optimization problem with credibilistic expected utility. Derived formulas for optimal allocation using various moments and utility function parameters.
result Different formulas for optimal allocation of risky assets are derived, considering fuzzy risk and utility function parameters.
Modern portfolio theory(MPT) addresses the problem of determining the optimum allocation of investment resources among a set of candidate assets. In the original mean-variance approach of Markowitz, volatility is taken as a proxy for risk, conflating uncertainty with risk. There have been many subsequent attempts to al…
Proposes a deep learning approach for optimizing portfolios with stocks and options.
problem Optimizing portfolios with time-inconsistent objectives and trading constraints.
method Neural networks with adaptive activation functions for asset allocation and option strike prices.
result Adding options leads to more stable and consistent stock allocations.
Study affine models for alternative risk-free rates and derive caplet pricing formulas.
problem Valuation of caplets/floorlets in models for alternative risk-free rates.
method Affine process for RFRs, explicit valuation formulas for various derivatives.
result Explicit formulas for caplet/floorlet pricing in affine models for RFRs.
The credit crisis and the ongoing European sovereign debt crisis have highlighted the native form of credit risk, namely the counterparty risk. The related Credit Valuation Adjustment, (CVA), Debt Valuation Adjustment (DVA), Liquidity Valuation Adjustment (LVA) and Replacement Cost (RC) issues, jointly referred to in t…
This paper presents hedging strategies for European and exotic options in a Levy market. By applying Taylor's Theorem, dynamic hedging portfolios are con- structed under different market assumptions, such as the existence of power jump assets or moment swaps. In the case of European options or baskets of European optio…
RL helps optimize TVS fund composition for volatility control.
problem Optimizing fund composition for target volatility strategy under uncertainty.
method Derive analytical solution for Black-Scholes model, use RL for local volatility model.
result RL agents' performance matches BS strategy in LV model.
A fuzzy expert system selects stocks for BSE using AI techniques.
problem Selecting stocks for investment allocation is challenging due to many influencing factors.
method Dempster-Shafer (DS) evidence theory for rule base generation, portfolio optimization model with ACO algorithm.
result The model's performance is satisfactory for short-term investment.
Study analyzes stock performance before, during, and after the pandemic.
problem Impact of the pandemic on stock performance and risk.
method Daily data of most traded companies in Colombia from 2015 to 2023, using minimum variance approach.
result Portfolio returns and risks varied significantly during the pandemic.
Derives a new formula for measuring risk aversion in markets.
problem Measuring the degree of risk aversion in markets accurately.
method Closed-form expression based on three variables: Treasury yields, returns, and market capitalization.
result Investors exhibit Decreasing Absolute Risk Aversion (DARA) but the degree of Relative Risk Aversion (RRA) varies.
The paper studies estimation of parameters of diffusion market models from historical data. The standard definition of implied volatility for these models presents its value as an implicit function of several parameters, including the risk-free interest rate. In reality, the risk free interest rate is unknown and need …
Study portfolio optimization with an exponential utility function and illiquid asset.
problem Optimizing a portfolio with a risk-free, liquid, and illiquid risky asset.
method Analytical substitution, Lie algebraic reduction, solving PDEs.
result Different optimization results for exponential utility function compared to HARA.
Management of the portfolios containing low liquidity assets is a tedious problem. The buyer proposes the price that can differ greatly from the paper value estimated by the seller, the seller, on the other hand, can not liquidate his portfolio instantly and waits for a more favorable offer. To minimize losses in this …
The CAPM's market returns are endogenously determined, affecting all assets' expected returns.
problem The standard CAPM's market return assumption is not endogenously consistent.
method Demonstrates the impact of endogenously determined market returns on asset returns and the range of feasible market returns.
result Expected returns are influenced by all assets' risks, and market returns are limited by asset distribution.
The study models financial derivatives with counterparty risk and corrects valuation methods.
problem Pricing financial derivatives considering counterparty credit risk and CVA.
method Developed a generic model for pricing derivatives with both unilateral and bilateral credit risks. Used backward induction for American style options. Emphasized that the market value is risky, not risk-free.
result Corrected the common mistake in the literature regarding the market value of defaultable derivatives.
This study shows how monetary uncertainty affects stock market reactions to macroeconomic news.
problem Understanding stock market reactions to macroeconomic news under varying levels of monetary uncertainty.
method Decomposes stock market response into cash flow and risk-free rate channels, analyzing time-varying effects.
result High monetary uncertainty weakens the positive stock market response to macroeconomic news.
Blockchain funds balance risk and return for various investors.
problem Creating diversified portfolios with risk parity for different risk appetites.
method Developed three funds (Alpha, Beta, Gamma) with distinct risk and return profiles, setting weights inversely proportional to risk.
result Blockchain enables investors to select their preferred risk-return combination and allocate wealth accordingly.
Method improves volatility targeting for index construction.
problem High turnover, leverage spikes, and sensitivity to estimation error in existing volatility-targeting strategies.
method Proportional-control approach for setting index weights that corrects tracking error through feedback.
result The proportional-control approach achieves the target volatility more effectively than open-loop alternatives.
In this paper, we continue our study on a general time-inconsistent stochastic linear--quadratic (LQ) control problem originally formulated in [6]. We derive a necessary and sufficient condition for equilibrium controls via a flow of forward--backward stochastic differential equations. When the state is one dimensional…
Research proposes a risk-free machine learning model for COVID screening from routine blood tests.
problem Rapid antigen tests have low sensitivity and are not suitable for widespread screening.
method Stacked Ensemble Machine Learning model using routine blood tests.
result 100% accuracy, precision, recall and F1-score in identifying COVID patients.
We provided an analytical representation of the price of a barrier option with one type of special moving barrier. We consider the case that risk free rate, dividend rate and stock volatility are time dependent. We get a pricing formula and put call parity for barrier option when the moving barrier has a special relati…
Management of a portfolio that includes an illiquid asset is an important problem of modern mathematical finance. One of the ways to model illiquidity among others is to build an optimization problem and assume that one of the assets in a portfolio can not be sold until a certain finite, infinite or random moment of ti…