Affine Dynamics with Torsion

In this study, we give a thorough analysis of a general affine gravity with torsion. After a brief exposition of the affine gravities considered by Eddington and Schr\"{o}dinger, we construct and analyze different affine gravities based on the determinants of the Ricci tensor, the torsion tensor, the Riemann tensor and their combinations. In each case we reduce equations of motion to their simplest forms and give a detailed analysis of their solutions. Our analyses lead to the construction of the affine connection in terms of the curvature and torsion tensors. Our solutions of the dynamical equations show that the curvature tensors at different points are correlated via non-local, exponential rescaling factors determined by the torsion tensor.Comment: 25 pages, typos correcte

Structural VAR identification in asset markets using short-run market inefficiencies

We impose a structure on the short-run market inefficiencies in the asset markets and use this structure to identify a structural vector autoregressive model. This novel identification method is based on more reasonable assumptions than the standard approaches and also gives estimates for inefficiency measures in the markets, which are important on their own. Applying our method on the major European stock markets, we find that while the UK shocks were dominant in Europe until 1999, German innovations have been more important since 1999. We also find that the pattern of inefficiencies are consistent with the rational inattention model of Sims (2003).Structural VAR; Overreaction and Underreaction; Stock Market

A Collaborative Kalman Filter for Time-Evolving Dyadic Processes

We present the collaborative Kalman filter (CKF), a dynamic model for collaborative filtering and related factorization models. Using the matrix factorization approach to collaborative filtering, the CKF accounts for time evolution by modeling each low-dimensional latent embedding as a multidimensional Brownian motion. Each observation is a random variable whose distribution is parameterized by the dot product of the relevant Brownian motions at that moment in time. This is naturally interpreted as a Kalman filter with multiple interacting state space vectors. We also present a method for learning a dynamically evolving drift parameter for each location by modeling it as a geometric Brownian motion. We handle posterior intractability via a mean-field variational approximation, which also preserves tractability for downstream calculations in a manner similar to the Kalman filter. We evaluate the model on several large datasets, providing quantitative evaluation on the 10 million Movielens and 100 million Netflix datasets and qualitative evaluation on a set of 39 million stock returns divided across roughly 6,500 companies from the years 1962-2014.Comment: Appeared at 2014 IEEE International Conference on Data Mining (ICDM

The necessity of subsidiarity for the realisation of urban conservation

It is known that during the last quarter of the 20th century, transformations towards globalisation is realized. Such a process has the quality changing the utilization form of the political power. In other words it indicates to a positive progression in democratization. Especially tendencies of "localization" is widely adopted beginning from international agreements like the European Charter for Local Self-Government and European Urban Charter. When localization is defined as the liberalization of the local-government from the hegemony of the central and subsidiarity with the participation and the control of the citizens, autonomy of the local governments gains importance. Parallel to this fact, a transformation from the government to governance is at the agenda of Turkey. In this sense, the concept of locality and its components (social/space wise processes locally originated) is revealed.Therefore, the continuity/conservation of cultural properties of a special place can not be managed with the continuity understanding of a central governmenti, as it can be mentioned that in conservation the economic/social/government aspects and even the lives of the users is substituted according to the needs of the day. Such a reality can only be known in place and be evaluated by the related citizens. The paper will include the situation in Turkiye in exemplary cases.

How Far Ahead Can We Forecast? Evidence From Cross-country Surveys

Using monthly GDP forecasts from Consensus Economics Inc. for 18 developed countries reported over 24 different forecast horizons during 1989-2004, we find that the survey forecasts do not have much value when the horizon goes beyond 18 months. Using two alternative approaches to measure the flow of new information in fixed-target survey forecasts, we found that the biggest improvement in forecasting performance comes when the forecast horizon is around 14 months. The dynamics of information accumulation over forecast horizons can provide both the forecasters and their clients with an important clue in their selection of the timing and frequency in the use of forecasting services. The limits to forecasting that these private market forecasters exhibit are indicative of the current state of macroeconomic foresight.

Estimating International Transmission of Shocks Using GDP Forecasts: India and Its Trading Partners

Using a Factor Structural Vector Autoregressive (FSVAR) model and monthly GDP growth forecasts during 1995-2003, we find that Indian economy responds largely to domestic and Asian common shocks, and much less to shocks the from the West. However, when we exclude the Asian crisis period from our sample, the Western factor comes out as strong as the Asian factor contributing 16% each to the Indian real GDP growth, suggesting that the dynamics of transmission mechanism is time-varying. Our methodology on the use of forecast data can help policy makers of especially developing countries with frequent economic crises and data limitations to adjust their policy targets in real time.

Scattering in abrupt heterostructures using a position dependent mass Hamiltonian

Transmission probabilities of the scattering problem with a position dependent mass are studied. After sketching the basis of the theory, within the context of the Schr\"{o}dinger equation for spatially varying effective mass, the simplest problem, namely, tranmission through a square well potential with a position dependent mass barrier is studied and its novel properties are obtained. The solutions presented here may be adventageous in the design of semiconductor devices.Comment: Eur. Phys. J. B. To be publishe

Oscillatory behavior of chromospheric fine structures in a network and a semi-active regions

In the present work, we study the periodicities of oscillations in dark fine structures using observations of a network and a semi-active region close to the solar disk center. We simultaneously obtained spatially high resolution time series of white light images and narrow band images in the H$\alpha$ line using the 2D G\"ottingen spectrometer, which were based on two Fabry-Perot interferometers and mounted in the VTT/Observatorio del Teide/Tenerife. During the observations, the H$\alpha$ line was scanned at 18 wavelength positions with steps of 125 m\AA. We computed series of Doppler and intensity images by subtraction and addition of the H$\alpha$ $\pm$ 0.3 \AA\ and $\pm$ 0.7 \AA\ pairs, sampling the upper chromosphere and the upper photosphere, respectively. Then we obtained power, coherence and phase difference spectra by performing a wavelet analysis to the Doppler fluctuations. Here, we present comparative results of oscillatory properties of dark fine structures seen in a network and a semi-active region.Comment: 8 pages, 5 figures, accepted for publication in MNRA