An Evaluation of Popular Copy-Move Forgery Detection Approaches

A copy-move forgery is created by copying and pasting content within the same image, and potentially post-processing it. In recent years, the detection of copy-move forgeries has become one of the most actively researched topics in blind image forensics. A considerable number of different algorithms have been proposed focusing on different types of postprocessed copies. In this paper, we aim to answer which copy-move forgery detection algorithms and processing steps (e.g., matching, filtering, outlier detection, affine transformation estimation) perform best in various postprocessing scenarios. The focus of our analysis is to evaluate the performance of previously proposed feature sets. We achieve this by casting existing algorithms in a common pipeline. In this paper, we examined the 15 most prominent feature sets. We analyzed the detection performance on a per-image basis and on a per-pixel basis. We created a challenging real-world copy-move dataset, and a software framework for systematic image manipulation. Experiments show, that the keypoint-based features SIFT and SURF, as well as the block-based DCT, DWT, KPCA, PCA and Zernike features perform very well. These feature sets exhibit the best robustness against various noise sources and downsampling, while reliably identifying the copied regions.Comment: Main paper: 14 pages, supplemental material: 12 pages, main paper appeared in IEEE Transaction on Information Forensics and Securit

1st INCF Workshop on Genetic Animal Models for Brain Diseases

The INCF Secretariat organized a workshop to focus on the “role of neuroinformatics in the processes of building, evaluating, and using genetic animal models for brain diseases” in Stockholm, December 13–14, 2009. Eight scientists specialized in the fields of neuroinformatics, database, ontologies, and brain disease participated together with two representatives of the National Institutes of Health and the European Union, as well as three observers of the national INCF nodes of Norway, Poland, and the United Kingdom

Constraining the Dark Energy Equation of State with Cosmic Voids

Our universe is observed to be accelerating due to the dominant dark energy with negative pressure. The dark energy equation of state (w) holds a key to understanding the ultimate fate of the universe. The cosmic voids behave like bubbles in the universe so that their shapes must be quite sensitive to the background cosmology. Assuming a flat universe and using the priors on the matter density parameter (Omega_m) and the dimensionless Hubble parameter (h), we demonstrate analytically that the ellipticity evolution of cosmic voids may be a sensitive probe of the dark energy equation of state. We also discuss the parameter degeneracy between w and Omega_m.Comment: ApJL in press, growth factor corrected, parameter degeneracy calculate

Constraining Perturbative Early Dark Energy with Current Observations

In this work, we study a class of early dark energy (EDE) models, in which, unlike in standard DE models, a substantial amount of DE exists in the matter-dominated era, self-consistently including DE perturbations. Our analysis shows that, marginalizing over the non DE parameters such as $Omega_m, H_0, n_s$, current CMB observations alone can constrain the scale factor of transition from early DE to late time DE to $a_t \geq 0.44$ and width of transition to $Delta_t \leq 0.37$. The equation of state at present is somewhat weakly constrained to $w_0 \leq -0.6$, if we allow $H_0 < 60$ km/s/Mpc. Taken together with other observations, such as supernovae, HST, and SDSS LRGs, the constraints are tighter-- $w_0 \leq -0.9, a_t \leq 0.19, \Delta_t \leq 0.21$. The evolution of the equation of state for EDE models is thus close to $\Lambda$CDM at low redshifts. Incorrectly assuming DE perturbations to be negligible leads to different constraints on the equation of state parameters, thus highlighting the necessity of self-consistently including DE perturbations in the analysis. If we allow the spatial curvature to be a free parameter, then the constraints are relaxed to $w_0 \leq -0.77, a_t \leq 0.35, \Delta_t \leq 0.35$ with $-0.014 < \Omega_{\kappa} < 0.031$ for CMB+other observations. For perturbed EDE models, the $2\sigma$ lower limit on $\sigma_8$ ($\sigma_8 \geq 0.59$) is much lower than that in $\Lambda$CDM ($\sigma_8 \geq 0.72$), thus raising the interesting possibility of discriminating EDE from $\Lambda$CDM using future observations such as halo mass functions or the Sunyaev-Zeldovich power spectrum.Comment: 12 pages, 5 figures, references updated, accepted for publication in Ap

Testing Gravity Against Early Time Integrated Sachs-Wolfe Effect

A generic prediction of general relativity is that the cosmological linear density growth factor $D$ is scale independent. But in general, modified gravities do not preserve this signature. A scale dependent $D$ can cause time variation in gravitational potential at high redshifts and provides a new cosmological test of gravity, through early time integrated Sachs-Wolfe (ISW) effect-large scale structure (LSS) cross correlation. We demonstrate the power of this test for a class of $f(R)$ gravity, with the form $f(R)=-\lambda_1 H_0^2\exp(-R/\lambda_2H_0^2)$. Such $f(R)$ gravity, even with degenerate expansion history to $\Lambda$CDM, can produce detectable ISW effect at z\ga 3 and l\ga 20. Null-detection of such effect would constrain $\lambda_2$ to be $\lambda_2>1000$ at $>95$ confidence level. On the other hand, robust detection of ISW-LSS cross correlation at high $z$ will severely challenge general relativity.Comment: 5 pages, 2 figures. Accepted to PRD. v2: Revised to address to more general audience. v3: added discussion