Heavy Higgs of the Twin Higgs Models

Twin Higgs models are the prime illustration of neutral naturalness, where the new particles of the twin sector, gauge singlets of the Standard Model (SM), ameliorate the little hierarchy problem. In this work, we analyse phenomenological implications of the heavy Higgs of the Mirror Twin Higgs and Fraternal Twin Higgs models, when electroweak symmetry breaking is linearly realized. The most general structure of twin Higgs symmetry breaking, including explicit soft and hard breaking terms in the scalar potential, is employed. The direct and indirect searches at the LHC are used to probe the parameter space of Twin Higgs models through mixing of the heavy Higgs with the SM Higgs and decays of the heavy Higgs to the SM states. Moreover, for the Fraternal Twin Higgs, we study the production and decays of twin glueball and bottomonium states to the SM light fermions, which have interesting signatures involving displaced vertices and are potentially observable at the colliders.Comment: 32+1 pages and 16 figures, v3: matches the version appeared in JHE

Brane modeling in warped extra-dimension

Five-dimensional scenarios with infinitesimally thin branes replaced by appropriate configurations of a scalar field were considered. A possibility of periodic extra dimension was discussed in the presence on non-minimal scalar-gravity coupling and a generalized Gibbons-Kallosh-Linde sum rule was found. In order to avoid constraints imposed by periodicity, a non-compact spacial extra dimension was introduced. A five dimensional model with warped geometry and two thin branes mimicked by a scalar profile was constructed and discussed. In the thin brane limit the model corresponds to a set-up with two positive-tension branes. The presence of two branes allows to address the issue of the hierarchy problem which could be solved by the standard warping of the four dimensional metric provided the Higgs field is properly localized. Stability of the background solution was discussed and verified in the presence of the most general perturbations of the metric and the scalar field.Comment: 38+1 pages and 5 figures; v2: some references added and matches the published version in JHE

The Determinants of Foreign Direct Investment in Pakistan

The paper empirically identifies the determinants of growth in foreign direct investment (FDI) in Pakistan over the period 1961–2003. Our main interest is to study how different variables or indicators reflecting the trade, fiscal, and financial sector liberalisation attract FDI in Pakistan. The study uses the cointegration and error-correction techniques to identify the variables in explaining the FDI in Pakistan. The study considers the tariff rate, exchange rate, tax rate, credit to private sector, and index of general share price variables to see if they may explain the inflow of foreign direct investment. Also included are wages and per capita GDP to test for the relative demand for labour and market size hypotheses. All variables indicate correct signs and are statistically significant except for wage rate and share price index. The study clearly emphasises the role of these policy variables in attracting FDI and determining its growth in both short- and long-run in Pakistan, and also indicates a positive and significant impact of reforms on FDI in Pakistan.Foreign Investment, Pakistan

Thick-Brane Cosmology

We search for time-dependent solutions for the 5-dimensional system of a scalar field canonically coupled to gravity. Time-independent and time-dependent scalar field configurations with the most general homogeneous and isotropic 4D metric are considered. For the case of time-independent scalar field, the time evolution of the scale factor is obtained for different values of the spatial curvature $k=0,\pm 1$. In the case of time-dependent scalar field, two classes of solutions are discussed and an extension of the superpotential formalism is proposed.Comment: 19 pages and 8 figures, v2: version published in JHE

The Twin Deficits Phenomenon: Evidence from Pakistan

Like most developing countries a steady budget deficit in Pakistan is the primary cause of all major ills of the economy. It has varied between 5.4 to 8.7 percent during last two decades. On the other hand the current account deficit varied between 2.7 to 7.2 percent during the same period. The variations in fiscal policy can lead to predictable developments in an open economy’s performance on current account, remains a controversial issue. An important aspect of this issue concerns what is termed as twin deficit analysis, according to which fiscal deficits and current account balances are very closely related so that reductions in the former are both necessary and sufficient to obtain improved performance in the later. Theoretical work on the relationship that exist between variations in fiscal policy and the current account balance has been based upon two types of models. These models are constructed from postulated behavioural relationships that purport to describe how the economy works in aggregate without explaining the behaviour of agents who make up the economy.

Generalized Randall-Sundrum model with a single thick brane

A generalized version of the Randall-Sundrum model-2 with different cosmological constants on each side of a brane has been discussed. A possibility of replacing the singular brane by a configuration of a scalar field has been also considered, the Einstein equations for this setup were solved and stability of the solution discussed. It has been shown that under mild assumptions the relation between cosmological constants and the brane tension obtained in the brane limit does not depend on the particular choice of the regularizing profile of the scalar field.Comment: 15 pages and 7 figures, v2: major revision in sections 2 and 3, results unchanged, version to appear in EPJ

Multi-scale modelling of macromolecular conformational changes

Modelling protein flexibility and plasticity is computationally challenging but important for understanding the function of biological systems. Furthermore, it has great implications for the prediction of (macro) molecular complex formation. Recently, coarse-grained normal mode approaches have emerged as efficient alternatives for investigating large-scale conformational changes for which more accurate methods like MD simulation are limited due to their computational burden. We have developed a Normal Mode based Simulation (NMSim) approach for efficient conformation generation of macromolecules. Combinations of low energy normal modes are used to guide a simulation pathway, whereas an efficient constraints correction approach is applied to generate stereochemically allowed conformations. Non-covalent bonds like hydrogen bonds and hydrophobic tethers and phi-psi favourable regions are also modelled as constraints. Conformations from our approach were compared with a 10 ns MD trajectory of lysozyme. A 2-D RMSD plot shows a good overlap of conformational space, and rms fluctuations of residues show a correlation coefficient of 0.78 between the two sets of conformations. Furthermore, a comparison of NMSim simulations starting from apo structures of different proteins show that ligand-bound conformations can be sampled for those cases where conformational changes are mainly correlated, e.g., domain-like motion in adenylate kinase. Efforts are currently being made to also model localized but functionally important motions for protein binding pockets and protein-protein interfaces using relevant normal mode selection criteria and implicit rotamer basin creation