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Now showing 1 - 4 of 4
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    PublicationOpen Access
    Inflation as a global phenomenon-nsome implications for inflation modelling and forecasting
    (Elsevier, 2018) Martinez-Garcia, Enrique; Department of Economics; Kabukçuoğlu, Ayşe; Faculty Member; Department of Economics; College of Administrative Sciences and Economics
    We model local inflation dynamics using global inflation and domestic slack motivated by a novel interpretation of the implications of the workhorse open-economy New Keynesian model. We evaluate the performance of inflation forecasts based on the single-equation forecasting specification implied by the model, exploiting the spatial pattern of international linkages underpinning global inflation. We find that incorporating cross-country interactions yields significantly more accurate forecasts of local inflation for a diverse group of 14 advanced countries (including the U.S.) than either a simple autoregressive model or a standard closed-economy Phillips curve-based forecasting model. We argue that modelling the temporal dimension—but not the cross-country spillovers—of inflation does limit a model’s explanatory power in-sample and its (pseudo) out-of-sample forecasting performance. Moreover, we also show that global inflation (without domestic slack) often contributes the most to achieve the gains on forecasting accuracy observed during our sample period (1984:Q1-2015:Q1)—this observation, according to theory, is crucially related to the flattening of the Phillips curve during this time period of increased globalization.
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    PublicationOpen Access
    On the complexity and approximation of the maximum expected value all-or-nothing subset
    (2018) Goldberg, Noam; Department of Industrial Engineering; Rudolf, Gabor; Faculty Member; Department of Industrial Engineering; College of Engineering
    An unconstrained nonlinear binary optimization problem of selecting a maximum expected value subset of items is considered. Each item is associated with a profit and probability. Each of the items succeeds or fails independently with the given probabilities, and the profit is obtained in the event that all selected items succeed. The objective is to select a subset that maximizes the total value times the product of probabilities of the chosen items. The problem is proven NP-hard by a nontrivial reduction from subset sum. Then we develop a fully polynomial time approximation scheme (FPTAS) for this problem.
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    PublicationOpen Access
    Quantum mechanics of a photon
    (American Institute of Physics (AIP) Publishing, 2017) Department of Physics; Department of Mathematics; Babaei, Hassan; Mostafazadeh, Ali; Faculty Member; Department of Physics; Department of Mathematics; Graduate School of Sciences and Engineering; N/A; 4231
    A first-quantized free photon is a complex massless vector field A = (A(mu)) whose field strength satisfies Maxwell's equations in vacuum. We construct the Hilbert space H of the photon by endowing the vector space of the fields A in the temporal-Coulomb gauge with a positive-definite and relativistically invariant inner product. We give an explicit expression for this inner product, identify the Hamiltonian for the photon with the generator of time translations in H, determine the operators representing the momentum and the helicity of the photon, and introduce a chirality operator whose eigenfunctions correspond to fields having a definite sign of energy. We also construct a position operator for the photon whose components commute with each other and with the chirality and helicity operators. This allows for the construction of the localized states of the photon with a definite sign of energy and helicity. We derive an explicit formula for the latter and compute the corresponding electric and magnetic fields. These turn out to diverge not just at the point where the photon is localized but on a plane containing this point. We identify the axis normal to this plane with an associated symmetry axis and show that each choice of this axis specifies a particular position operator, a corresponding position basis, and a position representation of the quantum mechanics of a photon. In particular, we examine the position wave functions determined by such a position basis, elucidate their relationship with the Riemann-Silberstein and Landau-Peierls wave functions, and give an explicit formula for the probability density of the spatial localization of the photon.
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    PublicationOpen Access
    Straddling two continents and beyond three worlds? The case of Turkey’s welfare regime
    (Cambridge University Press, 2017) Powell, Martin; Department of Sociology; Yörük, Erdem; Faculty Member; Department of Sociology; College of Social Sciences and Humanities; 28982
    This article aims to consider how Turkey has been classified in the welfare regime literature, and on what basis it has been classified. This will then form the basis for exploring whether there appears to be any variation between approaches and methods and/or between the “position” (e.g., location or language) of the authors. Studies of Turkey’s welfare regime exhibit a significant degree of variation in terms of both approaches and conclusions, resulting in little in the way of consensus. Among Turkish-language studies (and some, but not all, Turkish scholars writing in English), there does seem to be a broad consensus that Turkey may be classified as part of the Southern European welfare model, which squares with the modal conclusion of the English-language studies on the topic. However, some “regional” studies conclude that Turkey is part of the Middle East and North Africa (MENA) region, while many of the cluster analyses suggest a wide variety of clusters that are not geographically contiguous.