Phenomenological Constraints on Anomaly-Free Dark Matter Models

We study minimal benchmark models of dark matter with an extra anomaly-free U(1)' gauge boson Z'. We find model parameters that give rise to the correct cosmological dark matter density while evading the latest direct detection searches for dark matter scattering produced by the XENON1T experiment, including the effects of Z-Z' mixing. We also find regions of parameter space that evade the constraints from LHC measurements of dileptons and dijets, precision electroweak measurements, and LHC searches for monojet events with missing transverse energy. We study two benchmark Z' models with Y-sequential couplings to quarks and leptons, one with a vector-like coupling to the dark matter particle and one with an axial dark matter coupling. The vector-like model is extremely tightly constrained, with only a narrow allowed strip where $m_\chi \simeq M_{Z'}/2$, and the axial model is excluded within the parameter range studied. We also consider two leptophobic Z$^\prime$ benchmark models, finding again narrow allowed strips where $m_\chi \simeq M_{Z'}/2$ as well as more extended regions where $\log_{10} (m_\chi/ {\rm GeV}) \gtrsim 3.2$.Comment: 29 pages, 18 figures, 0 anomalie

Anomaly-Free Dark Matter Models are not so Simple

We explore the anomaly-cancellation constraints on simplified dark matter (DM) models with an extra U(1)$^\prime$ gauge boson $Z'$. We show that, if the Standard Model (SM) fermions are supplemented by a single DM fermion $\chi$ that is a singlet of the SM gauge group, and the SM quarks have non-zero U(1)$^\prime$ charges, the SM leptons must also have non-zero U(1)$^\prime$ charges, in which case LHC searches impose strong constraints on the $Z'$ mass. Moreover, the DM fermion $\chi$ must have a vector-like U(1)$^\prime$ coupling. If one requires the DM particle to have a purely axial U(1)$^\prime$ coupling, which would be the case if $\chi$ were a Majorana fermion and would reduce the impact of direct DM searches, the simplest possibility is that it is accompanied by one other new singlet fermion, but in this case the U(1)$^\prime$ charges of the SM leptons still do not vanish. This is also true in a range of models with multiple new singlet fermions with identical charges. Searching for a leptophobic model, we then introduce extra fermions that transform non-trivially under the SM gauge group. We find several such models if the DM fermion is accompanied by two or more other new fermions with non-identical charges, which may have interesting experimental signatures. We present benchmark representatives of the various model classes we discuss.Comment: 19 pages, 0 figures, this v2 matches version accepted for publicatio

Growth, Cycles and Welfare: A Schumpeterian Perspective

We use a Schumpeterian model in which both the economy's growth rate and its volatility are endogenously determined to assess some welfare and policy implications associated with business cycle fluctuations. Because it features a higher average growth rate than its acyclical counterpart, steady-state welfare is higher along the cyclical equilibrium growth path of the model. We assess the impact of alternative stabilization policies designed to smooth cyclical fluctuations. Although, it is possible to significantly reduce the variance of output growth via simple policy measures, the welfare benefits are at best negligible and at worst completely offset by the resulting reduction long-term productivity growth.Endogenous cycles, Endogenous growth, Welfare, Stabilization policy

Intrinsic Business Cycles with Pro-Cyclical R&D

Recent empirical work finds that R&D expenditures are quite procyclical, even for firms that are not redit-constrained during downturns. This has been taken as strong evidence against Schumpeterian-style theories of business cycles that emphasize the idea that downturns in production may be good times to allocate labor towards innovative activities. Here we argue that the procyclicality of R&D investment is, in fact, quite consistent with at least one of these theories. In our analysis, we emphasize three key features of R&D investment relative to other types of innovative activity: (1) it uses knowledge intensively, (2) it is a long-term investment with uncertain applications and (3) it suffers from diminishing returns over time.Schumpeterian, R&D investment, endogenous cycles, endogenous growth

I - Q Cycles

We develop a model of 'intrinsic' business cycles, driven by the decentralized behaviour of entrepreneurs and firms making continuous, divisible improvements in their productivity. We show how equilibrium cycles, associated with strategic delays in implementation and endogenous innovation, arise even in the presence of reversible investment. We derive the implications for the cyclical evolution of both tangible (physical) and intangible (knowledge) capital. In particular, our framework is consistent with key aspects of the somewhat puzzling relationship between fixed capital formation and the stockmarket at business cycle frequencies.Tobin's Q, fixed capital formation, intangible investment, cycles and growth

Animal Spirits meets Creative Destruction

We show how a Schumpeterian process of creative destruction can induce rational, herd-behavior by entrepreneurs across diverse sectors of the economy that may look like it is fuelled by ``animal spirits''. Consequently, a multi-sector economy, in which sector-specific, productivity improvements are made by independent, profit-seeking entrepreneurs, can exhibit regular booms, slowdowns and downturns as an inherent part of the long-run growth process. The cyclical equilibrium that we study has a higher average growth rate but lower welfare than the corresponding acyclical one. We find that the cycles generated by our model exhibit several features of actual business cycles, and that across cycling economies, a negative relationship emerges between volatility and growth. Nous montrons comment un processus de destruction créatrice Schumpeterien peut entraîner un comportement rationnel de masse ('moutonnier') des entrepreneurs à travers les différents secteurs de l'économie, un comportement qui peut apparaître comme provenant d'effets non fondamentaux ('esprits animaliers'). En conséquence, une économie avec des secteurs multiples dans laquelle les améliorations de productivité sont apportées par des entrepreneurs in-dépendants cherchant un profit peut être caractérisée par des expansions, des ralentissements et des baisses de façon régulière tout en étant une partie intégrante du processus de croissance à long terme. L'équilibre cyclique que nous étudions possède certes un taux de croissance moyen supérieur mais également un niveau de bien-être inférieur par rapport à l'équilibre acyclique correspondant. Nous trouvons que les cycles générés par notre modèle présentent plusieurs caractéristiques des cycles économiques observés dans les données et qu'une relation négative émerge entre la volatilité et la croissance parmis les économies caractérisées par des cycles.Entrepreneurship, innovation, endogenous business cycles, endogenous growth

Investment Cycles

It is common amonst macroeconomists to view aggregate investment fluctuations as a rational response to fluctuating incentives, driven by exogenous movements in total factor productivity. However, this approach raises a number of questions. Why treat investments in physical capital as endogenous, while treating those in intangible capital as exogenous? Relatedly, why would productivity changes exhibit such strong co- movement across diverse sectors of the economy, and why are the short- run, empirical relationships between aggregate investment and measures of investment incentives, such as Tobin's Q, so weak? We address these and other related issues using a model of 'implementation cycles' that incorporates physical capital. In doing so, we demonstrate the crucial role played by endogenous innovation and incomplete contracting, inherent to the process of creative destruction.Inflexibility of installed capital, Tobin's Q, recessions, endogenous cycles and growth

Mary Lawton Metcalfe

Mary Lawton Metcalfe began writing for The Moving Picture News, a New York City-based trade journal, in 1911. This was, according to available materials, her first foray into film writing, although she had served as an advice columnist in a regional publication—“the Dorothy Dix of the Staten Island World” (MacDonald 1911, 7). At first glance, Metcalfe’s essays appear to be atypically strident advocacy pieces for the moral reform of cinema, and for the use of moving pictures in education: “This is a bomb I am going to throw right into educational circles,” she threatened—the bomb of moving pictures (“A Practical Plan” 6). In a May 1912 article, she proposed that every university, public library, Sunday school, and church have a motion picture projector, and this at a time when such proposals were unorthodox (28). Reading her essays and non-film-related writing more closely, it becomes clear that Metcalfe’s advocacy was premised upon an interlocking, sui generis theory of film. Cumulatively, she called for an entirely new, curative cinema, one that would encourage moviegoers to develop the right thoughts by which they could be physically improved: she called for a cinema that doubled as a medicine