Computing the partition function of the Sherrington-Kirkpatrick model is hard on average

We establish the average-case hardness of the algorithmic problem of exact computation of the partition function associated with the Sherrington-Kirkpatrick model of spin glasses with Gaussian couplings and random external field. In particular, we establish that unless $P= \#P$, there does not exist a polynomial-time algorithm to exactly compute the partition function on average. This is done by showing that if there exists a polynomial time algorithm, which exactly computes the partition function for inverse polynomial fraction ($1/n^{O(1)}$) of all inputs, then there is a polynomial time algorithm, which exactly computes the partition function for all inputs, with high probability, yielding $P=\#P$. The computational model that we adopt is {\em finite-precision arithmetic}, where the algorithmic inputs are truncated first to a certain level $N$ of digital precision. The ingredients of our proof include the random and downward self-reducibility of the partition function with random external field; an argument of Cai et al. \cite{cai1999hardness} for establishing the average-case hardness of computing the permanent of a matrix; a list-decoding algorithm of Sudan \cite{sudan1996maximum}, for reconstructing polynomials intersecting a given list of numbers at sufficiently many points; and near-uniformity of the log-normal distribution, modulo a large prime $p$. To the best of our knowledge, our result is the first one establishing a provable hardness of a model arising in the field of spin glasses. Furthermore, we extend our result to the same problem under a different {\em real-valued} computational model, e.g. using a Blum-Shub-Smale machine \cite{blum1988theory} operating over real-valued inputs.Comment: 31 page

Electrospinning Functional Polyacrylonitrile Nanofibers with Polyaniline, Carbon Nanotubes, and Silver Nitrate as Additives

Electrospinning of composite nanofibers has been attracting great attention as a way of producing functional nanofibers. Composite nanofibers are produced with the incorporation of the additives into the polymer melt/solution before electrospinning process and reported to show many superior properties such as high modulus, increased strength, improved thermal stability, or some new functionalities such as flame retardancy, antimicrobial properties, water repellency, soil resistance, decreased gas permeability, electromagnetic shielding, electrical conductivity, and so on. The availability of the wide range of additives makes it possible to produce a wide range of functional nanocomposite nanofibers that are promising for various applications. Polyaniline (PANI) as an inherently conductive polymer is being investigated as an additive for improving conductivity. Carbon nanotubes (CNT) are widely used for either their reinforcement ability or their superior electrical conductivity. Silver nanoparticles (AgNPs) are being incorporated into polymer matrices to obtain antibacterial activity. This chapter provides a comprehensive review about polyacrylonitrile (PAN) nanofibers with PANI, CNTs, AgNPs, and their combinations and highlights the synergistic effects obtained by their combined use

A Comparative Analysis of Knowledge Management in Banking Sector: An Empirical Research

Knowledge management is defined as the process of creating, storing, transferring, applying and saving organizational knowledge. Especially, in an environment of intensive competition increased with globalization; creating knowledge has been a vital factor for organizations, which want to gain advantage by innovative production. The development of information and communication technologies has accelerated this process. All of these developments attracted attention to the concept of knowledge, and a new period, in which the organizations that can create knowledge and use this acquired knowledge effectively and efficiently, have competitive advantage started. In this process, technology, organizational culture, leadership and measurement became important as basic components to provide effectiveness and efficiency in knowledge management. The main purpose of this study is to examine the basic components of knowledge management in banking sector with an empirical analysis and also to determine whether there is a difference between the private and state banks in the context of knowledge management practices. Key Words: Knowledge Management, Knowledge Management Components, Knowledge Management Process, Information Technologies, Banking Secto

Rising from the Ashes of COVID-19 will Need a Sharp Focus on the Numbers

If there is one sector that cannot move \u27online\u27, it is accommodation, and SLEs (small lodging establishments) have taken a merciless beating from COVID-19. Typically family-owned and managed, they have relatively high capital costs and overheads which means that even when revenues stop coming in, those liabilities still have to be met. This study by Dr. Manuel Rivera, Dr. Murat Kizildag, and Dr. Robertico Croes, of the Rosen College of Hospitality Management, shows how a detailed break-even analysis can inform a business’s strategy for survival within the important SLE sector

CORPORATE GOVERNANCE, OWNERSHIP STRUCTURE, AND CREDIT RATINGS OF HOSPITALITY FIRMS

This study examines interrelated connections of corporate governance, ownership structure, and credit ratings. From the agency relationship perspective, the study analyzes this multiple association by accounting for firm-specific and ownership characteristics for the period between 1990 and 2007. In this context, logistic functions are used in regression models to predict the probable outcomes of these multiple relationships. Primary findings of this study revealed that hospitality firms with higher anti-takeover provisions (less shareholder power) enjoy higher credit ratings. Findings also revealed high coefficients of Gompers, Ishii, and Metrick (2003) index (the GIM index), suggesting that hospitality firms have strong governance provisions, reduced agency conflicts, and higher chances of getting better credit ratings

Restaurants Post COVID-19

When you’re suddenly forced to close 1,800 restaurant dining rooms without any certainty of being able to reopen them any time soon, you need to act decisively and prioritize if you plan to be around for a grand reopening. For Darden Restaurants and their market-leading US brands, those priorities during lockdown were ‘look after the people – look after the cash!’ Dr. Elizabeth Yost, Dr. Murat Kizildag and Dr. Jorge Ridderstaat of UCF Rosen College of Hospitality Management investigate the company’s achievement

Recent Advances in Applications of Ceramic Nanofibers

Ceramic materials are well known for their hardness, inertness, superior mechanical and thermal properties, resistance against chemical erosion and corrosion. Ceramic nanofibers were first manufactured through a combination of electrospinning with sol–gel method in 2002. The electrospun ceramic nanofibers display unprecedented properties such as high surface area, length, thermo-mechanical properties, and hierarchically porous structure which make them candidates for a wide range of applications such as tissue engineering, sensors, water remediation, energy storage, electromagnetic shielding, thermal insulation materials, etc. This chapter focuses on the most recent advances in the applications of ceramic nanofibers

Corporate Real Estate Holdings and Financial Performance of Restaurant Firms

Most restaurant firms, by their operational nature, own and operate a large amount of corporate real estate (CRE), even though real estate is not their primary business activity. This is not only common across restaurant firms of different sizes but also linked to their sales and profitability. Borrowing the arguments of resource-based theory and using financial data for the years between 1999 and 2014, this study investigated the relationship between CRE holdings and restaurant firm performance in the United States. Briefly, our findings demonstrate that the CRE ratio and the rent ratio, in particular, have different impacts on restaurant firms’ financial performance and market-driven risk structures when different forward lags are considered

How Is the Premium Calibrated for the Speculative Risk in Lodging Firms?

The overarching themes of our paper are to calibrate the risk premium relative to the speculative risk parameters in capital markets and to analyze the pre-and post-recession patterns in the U.S. lodging portfolios from 2000 to 2016. We decompose several risk parameters speculated by the markets and risk-adjusted proxies to make solid judgments about the anomalies in excess return patterns and risk-reward trade-off calibration in our annualized heterogeneous portfolio sorts. Our primary findings reveal that our portfolio sorts did not return the efficient premium to the investors, as they should have been based on the speculative risk levels before the recession. However, after the recession, there was a correction in this pattern. Lastly, speculative risk-adjusted proxies and risk parameters generally co-move with the value-weighted benchmark

Development of a multi-functional ventilated façade with an integrated collector-storage: numerical model and experimental facility

The paper reports on physical modeling and experimental evaluation of glazed systems. A multi-functional ventilated façade with an integrated collector-storage is developed and mounted on a test cell facility under real weather conditions. The component uses solar radiation to produce solar heated water flow, which in turn can provide space heating or fulfill domestic hot water demands. Different operational modes of the ventilation channel are analyzed in order to improve the thermal performance of the buildings with glazed façades. The existing numerical platform for the prediction of the thermal performance of buildings and solar systems is used to implement a numerical model to address the multi-functional ventilated façade with integrated collector-storage element. The model uses the measured outdoor data as boundary conditions to obtain predictions by means of a general energy balance in the test room and the façade component. The model permits different levels of simulation depending on the desired precision in each element, applying a modular methodology. In this study, the convection heat transfer coefficient within the parallelepiped storage tank is obtained from a direct numerical simulation (DNS) of turbulent natural convection flow of water, while the remaining empirical information is obtained from the literature for similar geometries.Peer ReviewedPostprint (author’s final draft