Essays in Asset Pricing and Volatility Risk

In the first chapter (``Good and Bad Uncertainty: Macroeconomic and Financial Market Implications\u27\u27 with Ivan Shaliastovich and Amir Yaron) we decompose aggregate uncertainty into `good\u27 and `bad\u27 volatility components, associated with positive and negative innovations to macroeconomic growth. We document that in line with our theoretical framework, these two uncertainties have opposite impact on aggregate growth and asset prices. Good uncertainty predicts an increase in future economic activity, such as consumption, and investment, and is positively related to valuation ratios, while bad uncertainty forecasts a decline in economic growth and depresses asset prices. The market price of risk and equity beta of good uncertainty are positive, while negative for bad uncertainty. Hence, both uncertainty risks contribute positively to risk premia. In the second chapter (``A Tale of Two Volatilities: Sectoral Uncertainty, Growth, and Asset-Prices\u27\u27) I document several novel empirical facts: Technological volatility that originates from the consumption sector plays the ``traditional\u27\u27 role of depressing the real economy and stock prices, whereas volatility that originates from the investment sector boosts prices and growth; Investment (consumption) sector\u27s technological volatility has a positive (negative) market-price of risk; Investment sector\u27s technological volatility helps explain return spreads based on momentum, profitability, and Tobin\u27s Q. I show that a standard DSGE two-sector model fails to fully explain these findings, while a model that features monopolistic power for firms and sticky prices, can quantitatively explain the differential impact of sectoral volatilities on real and financial variables. In the third chapter (``From Private-Belief Formation to Aggregate-Vol Oscillation\u27\u27) I propose a model that relies on learning and informational asymmetry, for the endogenous amplification of the conditional volatility in macro aggregates and of cross-sectional dispersion during economic slowdowns. The model quantitatively matches the fluctuations in the conditional volatility of macroeconomic growth rates, while generating realistic real business-cycle moments. Consistently with the data, shifts in the correlation structure between firms are an important source of aggregate volatility fluctuations. Cross-firm correlations rise in downturns due to a higher weight that firms place on public information, which causes their beliefs and policies to comove more strongly

Good and Bad Uncertainty: Macroeconomic and Financial Market Implications

Does macroeconomic uncertainty increase or decrease aggregate growth and asset prices? To address this question, we decompose aggregate uncertainty into ‘good’ and ‘bad’ volatility components, associated with positive and negative innovations to macroeconomic growth. We document that in line with our theoretical framework, these two uncertainties have opposite impact on aggregate growth and asset prices. Good uncertainty predicts an increase in future economic activity, such as consumption, output, and investment, and is positively related to valuation ratios, while bad uncertainty forecasts a decline in economic growth and depresses asset prices. Further, the market price of risk and equity beta of good uncertainty are positive, while negative for bad uncertainty. Hence, both uncertainty risks contribute positively to risk premia, and help explain the cross-section of expected returns beyond cash flow risk

Altitude-Loss Optimal Glides in Engine Failure Emergencies -- Accounting for Ground Obstacles and Wind

Engine failure is a recurring emergency in General Aviation and fixed-wing UAVs, often requiring the pilot or remote operator to carry out carefully planned glides to safely reach a candidate landing strip. We tackle the problem of minimizing the altitude loss of a thrustless aircraft flying towards a designated target position. Extending previous work on optimal glides without obstacles, we consider here trajectory planning of optimal gliding in the the presence of ground obstacles, while accounting for wind effects. Under simplifying model assumptions, in particular neglecting the effect of turns, we characterize the optimal solution as comprising straight glide segments between iteratively-determined extreme points on the obstacles. Consequently, the optimal trajectory is included in an iteratively-defined reduced visibility graph, and can be obtained by a standard graph search algorithm, such as A$^*$. We further quantify the effect of turns to verify a safe near-optimal glide trajectory. We apply our algorithm on a Cessna 172 model, in realistic scenarios, demonstrating both the altitude-loss optimal trajectory calculation, and determination of airstrip reachability

Operant down-conditioning of the soleus H-reflex in people after stroke

Through operant conditioning, spinal reflex behaviors can be changed. Previous studies in rats indicate that the sensorimotor cortex and corticospinal tract are essential in inducing and maintaining reflex changes induced through conditioning. In people with incomplete spinal cord injury (SCI), an operant down-conditioning protocol decreased the soleus H-reflex size and improved walking speed and symmetry, suggesting that a partially preserved spinal cord can support conditioning-induced plasticity and benefit from it. This study examined whether down-conditioning can decrease the soleus H-reflex in people with supraspinal injury (i.e., cortical or subcortical stroke). Operant down-conditioning was applied to the soleus H-reflex in a cohort of 12 stroke people with chronic spastic hemiparesis (>12 months from stroke onset of symptoms). Each participant completed 6 baseline and 30 conditioning sessions over 12 weeks. In each baseline session, 225 control H-reflexes were elicited without any feedback on H-reflex size. In each conditioning session, 225 conditioned H-reflexes were elicited while the participant was asked to decrease H-reflex size and was given visual feedback as to whether the resulting H-reflex was smaller than a criterion value. In six of 12 participants, the conditioned H-reflex became significantly smaller by 30% on average, whereas in other 6 participants, it did not. The difference between the subgroups was largely attributable to the difference in across-session control reflex change. Ten-meter walking speed was increased by various extent (+0.04 to +0.35, +0.14 m/s on average) among the six participants whose H-reflex decreased, whereas the change was 0.00 m/s on average for the rest of participants. Although less than what was seen in participants with SCI, the fact that conditioning succeeded in 50% of stroke participants supports the feasibility of reflex down-conditioning in people after stroke. At the same time, the difference in across-session control reflex change and conditioning success rate may reflect a critical role of supraspinal activity in producing long-term plasticity in the spinal cord, as previous animal studies suggested

Foundations for Relativistic Quantum Theory I: Feynman's Operator Calculus and the Dyson Conjectures

In this paper, we provide a representation theory for the Feynman operator calculus. This allows us to solve the general initial-value problem and construct the Dyson series. We show that the series is asymptotic, thus proving Dyson's second conjecture for QED. In addition, we show that the expansion may be considered exact to any finite order by producing the remainder term. This implies that every nonperturbative solution has a perturbative expansion. Using a physical analysis of information from experiment versus that implied by our models, we reformulate our theory as a sum over paths. This allows us to relate our theory to Feynman's path integral, and to prove Dyson's first conjecture that the divergences are in part due to a violation of Heisenberg's uncertainly relations

Gender and class in Britain and France

This article examines the treatment of women's oppression in feminist theory, focusing on the engagement of second wave feminists with the concept of class and its relation to gender. This examination is carried out with reference to British and French feminisms, identifying the main trends and shifts that have developed over the last 35 years and noting that while these are undoubtedly influenced by a particular national context they are also shaped by increasing European integration and social, political and cultural exchanges at a global level. The authors find evidence of a number of similarities in the questions that feminist theorists have asked in Britain and France but also demonstrate that there are significant differences. They conclude that areas of convergent theoretical interests will extend along with cross-border flows of peoples and information

Recognition and the Character of Seneca's Medea

This article examines the character and identity of Seneca's Medea. Focusing on the recognition scene at the end of the play, I investigate how Medea constructs herself both as a literary figure and as an implied human personality. The concluding scene of Seneca's Medea raises crucial questions about self-coherence and recognisability: in contrast to other moments of anagnōrisis in Greco-Roman drama, it confirms the pre-existing facets of Medea's identity, rather than revealing new ones. This concept of recognition as self-confirmation is also integral to Seneca's Stoic view of human selfhood, and Medea's use of Stoic principles in this play reinforces her dual status as textual entity and quasi-person

Antibiotic resistance in the environment, with particular reference to MRSA

The introduction of β-lactam antibiotics (penicillins and cephalosporins) in the 1940s and 1950s probably represents the most dramatic event in the battle against infection in human medicine. Even before widespread global use of penicillin, resistance was already recorded. E. coli producing a penicillinase was reported in Nature in 1940 (Abraham, 1940) and soon after a similar penicillinase was discovered in Staphylococcus aureus (Kirby, 1944). The appearance of these genes, so quickly after the discovery and before the widespread introduction of penicillin, clearly shows that the resistance genes pre-dated clinical use of the antibiotic itself

Imagining Gendered Adulthood

In this article, the authors draw on two qualitative, longitudinal studies of young people’s transitions to adulthood and how they construct these transitions over time in social, cultural and material terms. The authors focus on the hopes, anxieties and imagined futures of young women. They discuss the individualization thesis, and the contradiction for female individualization between expectations of equality and the reality of inequality between the genders. The debate is moved beyond ‘pitiful girls’ and ‘can-do girls’ by exploring how young women in the UK and Finland anticipate and try to avoid being locked into the lives of adult women

Why “intergenerational feminist media studies”?

Feminism and generation are live and ideologically freighted issues that are subject to a substantial amount of media engagement. The figure of the millennial and the baby boomer, for example, regularly circulate in mainstream media, often accompanied by hyperbolic and vitriolic discourses and affects of intergenerational feminist conflict. In addition, theories of feminist generation and waves have been and continue to be extensively critiqued within feminist theory. Given the compelling criticisms directed at these categories, we ask: why bother examining and foregrounding issues of generation, intergeneration, and transgeneration in feminist media studies? Whilst remaining sceptical of linearity and familial metaphors and of repeating reductive, heteronormative, and racist versions of feminist movements, we believe that the concept of generation does have critical purchase for feminist media scholars. Indeed, precisely because of the problematic ways that is it used, and the prevalence of it as a volatile, yet only too palpable, organizing category, generation is both in need of continual critical analysis, and is an important tool to be used—with care and nuance—when examining the multiple routes through which power functions in order to marginalize, reward, and oppress. Exploring both diachronic and synchronic understandings of generation, this article emphasizes the use of conjunctural analysis to excavate the specific historical conditions that impact upon and create generation. This special issue of Feminist Media Studies covers a range of media forms—film, games, digital media, television, print media, as well as practices of media production, intervention, and representation. The articles also explore how figures at particular lifestages—particularly the girl and the aging woman—are constructed relationally, and circulate, within media, with particular attention to sexuality. Throughout the issue there is an emphasis on exploring the ways in which the category of generation is mobilized in order to gloss sexism, racism, ageism, class oppression, and the effects of neoliberalism