Results for "M. S. Bahramy"

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Origin of giant bulk Rashba splitting: Application to BiTeIMay 13 2011We theoretically propose the necessary conditions for realization of giant Rashba splitting in bulk systems. In addition to (i) the large atomic spin-orbit interaction in an inversion-asymmetric system, the following two conditions are further required; ... More
Emergence of non-centrosymmetric topological insulating phase in BiTeI under pressureSep 23 2011Feb 14 2012The spin-orbit interaction affects the electronic structure of solids in various ways. Topological insulators are one example where the spin-orbit interaction leads the bulk bands to have a non-trivial topology, observable as gapless surface or edge states. ... More
Mechanism of charge transfer/disproportionation in LnCu3Fe4O12 (Ln: Lanthanides)Mar 26 2014The Fe-Cu intersite charge transfer and Fe charge disproportionation are interesting phenomena observed in some LnCu3Fe4O12 (Ln: Lanthanides) compounds containing light and heavy Ln atoms, respectively. We show that a change in the spin state is responsible ... More
Calculations of spin induced transport in ferromagnetsOct 29 2006Dec 12 2006Based on first-principles density functional calculations, a general approach for determining and analyzing the degree of spin polarization (P) in ferromagnets is presented. The approach employs the so-called tetrahedron method to evaluate the Fermi surface ... More
Superconductivity in Cu$_{x}$IrTe$_{2}$ induced by interlayer hybridizationDec 26 2012The change in the electronic structure of layered Cu$_{x}$IrTe$_{2}$ has been characterized by transport and spectroscopic measurements, combined with first-principles calculations. The Cu-intercalation suppresses the monoclinic distortion, giving rise ... More
Spin-orbit coupling, minimal model and potential Cooper-pairing from repulsion in BiS$_2$-superconductorsNov 15 2017We develop the realistic minimal electronic model for recently discovered BiS$_2$ superconductors including the spin-orbit coupling based on a first-principles band structure calculations. Due to strong spin-orbit coupling, characteristic for the Bi-based ... More
Observation of Zeeman effect in topological surface state with distinct material dependenceJan 08 2016Jan 11 2016The helical Dirac fermions on the surface of topological insulators host novel relativistic quantum phenomena in solids. Manipulating spins of topological surface state (TSS) represents an essential step towards exploring the theoretically predicted exotic ... More
Anticorrelation between polar lattice instability and superconductivity in the Weyl semimetal candidate MoTe2Mar 08 2017The relation between the polar structural instability and superconductivity in a Weyl semimetal candidate MoTe2 has been clarified by finely controlled physical and chemical pressure. The physical pressure as well as the chemical pressure, i.e., the Se ... More
Mechanisms of enhanced orbital dia- and paramagnetism: Application to the Rashba semiconductor BiTeINov 24 2011Aug 31 2012We study the magnetic susceptibility of a layered semiconductor BiTeI with giant Rashba spin splitting both theoretically and experimentally to explore its orbital magnetism. Apart from the core contributions, a large temperature-dependent diamagnetic ... More
Observation of spin-polarized bands and domain-dependent Fermi arcs in polar Weyl semimetal MoTe$_2$Nov 07 2016Mar 07 2017We investigate the surface electronic structures of polar 1T'-MoTe2, the Weyl semimetal candidate realized through the nonpolar-polar structural phase transition, by utilizing the laser angle-resolved photoemission spectroscopy (ARPES) combined with first-principles ... More
Observation of spin-polarized bands and domain-dependent Fermi arcs in polar Weyl semimetal MoTe$_2$Nov 07 2016We investigate the surface electronic structures of 1T'-MoTe2, the Weyl semimetal candidate realized through the nonpolar-polar structural phase transition, by utilizing the laser angle-resolved photoemission spectroscopy (ARPES) combined with first-principles ... More
Band Structure and Spin-Orbital Texture of the (111)-KTaO3 Two-Dimensional Electron GasMar 14 2019Two-dimensional electron gases (2DEGs) in oxides show great potential for discovering new physical phenomena and at the same time hold promise for electronic applications. In this work we use angle resolved photoemission to determine the electronic structure ... More
Emergent quantum confinement at topological insulator surfacesJun 04 2012Bismuth-chalchogenides are model examples of three-dimensional topological insulators. Their ideal bulk-truncated surface hosts a single spin-helical surface state, which is the simplest possible surface electronic structure allowed by their non-trivial ... More
Control of a two-dimensional electron gas on SrTiO3(111) by atomic oxygenMay 13 2014We report on the formation of a two-dimensional electron gas (2DEG) at the bare surface of (111) oriented SrTiO3. Angle resolved photoemission experiments reveal highly itinerant carriers with a 6-fold symmetric Fermi surface and strongly anisotropic ... More
Evolution of electronic states and emergence of superconductivity in the polar semiconductor GeTe by doping valence-skipping InJan 25 2019GeTe is a chemically simple IV-VI semiconductor which bears a rich plethora of different physical properties induced by doping and external stimuli. These include, among others, ferromagnetism, ferroelectricity, phase-change memory functionality, and ... More
Quasiparticle dynamics and spin-orbital texture of the SrTiO3 two-dimensional electron gasMar 03 2014Sep 07 2014Two-dimensional electron gases (2DEGs) in SrTiO$_3$ have become model systems for engineering emergent behaviour in complex transition metal oxides. Understanding the collective interactions that enable this, however, has thus far proved elusive. Here ... More
Dual quantum confinement and anisotropic spin splitting in the multi-valley semimetal PtSe$_2$Dec 11 2018Feb 25 2019We investigate the electronic structure of a two-dimensional electron gas created at the surface of the multi-valley semimetal 1T-PtSe$_2$. Using angle-resolved photoemission and first-principles-based surface space charge calculations, we show how the ... More
Giant magneto-optical response in non-magnetic semiconductor BiTeI driven by bulk Rashba spin splittingMay 18 2012We study the magneto-optical (MO) response of polar semiconductor BiTeI with giant bulk Rashba spin splitting at various carrier densities. Despite being non-magnetic, the material is found to yield a huge MO activity in the infrared region under moderate ... More
Dual quantum confinement and anisotropic spin splitting in the multi-valley semimetal PtSe$_2$Dec 11 2018We investigate the electronic structure of a two-dimensional electron gas created at the surface of the multi-valley semimetal 1T-PtSe$_2$. Using angle-resolved photoemission and first-principles-based surface space charge calculations, we show how the ... More
Strongly spin-orbit coupled two-dimensional electron gas emerging near the surface of polar semiconductorsDec 07 2012We investigate the two-dimensional (2D) highly spin-polarized electron accumulation layers commonly appearing near the surface of n-type polar semiconductors BiTeX (X = I, Br, and Cl) by angular-resolved photoemission spectroscopy. Due to the polarity ... More
Observation of out-of-plane spin texture in a SrTiO3 (111) two-dimensional electron gasJun 05 2018We explore the second order bilinear magnetoelectric resistance (BMER) effect in the d-electron-based two-dimensional electron gas (2DEG) at the SrTiO3 (111) surface. We find an evidence of a spin-split band structure with the archetypal spin-momentum ... More
Direct observation of spin-polarised bulk bands in an inversion-symmetric semiconductorAug 28 2014Methods to generate spin-polarised electronic states in non-magnetic solids are strongly desired to enable all-electrical manipulation of electron spins for new quantum devices. This is generally accepted to require breaking global structural inversion ... More
Absence of Giant Spin Splitting in the Two-Dimensional Electron Liquid at the Surface of SrTiO$_3$ (001)Mar 01 2016We reinvestigate the putative giant spin splitting at the surface of SrTiO$_3$ reported by Santander-Syro $et~al.$ [Nature Mat. 13, 1085 (2014)]. Our spin- and angle-resolved photoemission experiments on (001) oriented surfaces supporting a two-dimensional ... More
Three-dimensional bulk band dispersion in polar BiTeI with giant Rashba-type spin splittingMay 14 2012In layered polar semiconductor BiTeI, giant Rashba-type spin-split band dispersions show up due to the crystal structure asymmetry and the strong spin-orbit interaction. Here we investigate the 3-dimensional (3D) bulk band structures of BiTeI using the ... More
Subband structure of a two-dimensional electron gas formed at the polar surface of the strong spin-orbit perovskite KTaO$_3$Nov 11 2011We demonstrate the formation of a two-dimensional electron gas (2DEG) at the $(100)$ surface of the $5d$ transition-metal oxide KTaO$_3$. From angle-resolved photoemission, we find that quantum confinement lifts the orbital degeneracy of the bulk band ... More
A general route to form topologically-protected surface and bulk Dirac fermions along high-symmetry linesFeb 25 2019The band inversions that generate the topologically non-trivial band gaps of topological insulators and the isolated Dirac touching points of three-dimensional Dirac semimetals generally arise from the crossings of electronic states derived from different ... More
Ubiquitous formation of bulk Dirac cones and topological surface states from a single orbital manifold in transition-metal dichalcogenidesFeb 27 2017Jul 19 2018Transition-metal dichalcogenides (TMDs) are renowned for their rich and varied properties. They range from metals and superconductors to strongly spin-orbit-coupled semiconductors and charge-density-wave systems, with their single-layer variants one of ... More
Spin-valley locking in the normal state of a transition-metal dichalocogenide superconductorMar 16 2016The metallic transition-metal dichalcogenides (TMDCs) are benchmark systems for studying and controlling intertwined electronic orders in solids, with superconductivity developing upon cooling from a charge density wave state. The interplay between such ... More
Fermiology and Superconductivity of Topological Surface States in PdTe$_2$Dec 12 2017Apr 16 2018We study the low-energy surface electronic structure of the transition-metal dichalcogenide superconductor PdTe$_2$ by spin- and angle-resolved photoemission, scanning tunneling microscopy, and density-functional theory-based supercell calculations. Comparing ... More
Epitaxially Stabilized EuMoO3: A New Itinerant FerromagnetSep 10 2012Synthesizing metastable phase often opens new functions in materials but is a challenging topic. Thin film techniques have advantages to form materials which do not exist in nature since nonequilibrium processes are frequently utilized. In this study, ... More
Rich structural phase diagram and thermoelectric properties of layered tellurides Mo1-xNbxTe2Feb 19 2015MoTe2 is a rare transition-metal ditelluride having two kinds of layered polytypes, hexagonal structure with trigonal prismatic Mo coordination and monoclinic structure with octahedral Mo coordination. The monoclinic distortion in the latter is caused ... More
Topological protection of bound states against the hybridizationDec 23 2012Dec 27 2012Topological invariants are conventionally known to be responsible for protection of extended states against disorder. A prominent example is the presence of topologically protected extended-states in two-dimensional (2D) quantum Hall systems as well as ... More
Giant thermoelectric effect in graphene-based topological insulators with nanoporesMar 02 2014Designing thermoelectric materials with high figure of merit $ZT=S^2 G T/\kappa$ requires fulfilling three often irreconcilable conditions, i.e., the high electrical conductance $G$, small thermal conductance $\kappa$ and high Seebeck coefficient $S$. ... More
Theory of topological quantum phase transitions in 3D noncentrosymmetric systemsJul 26 2012Mar 02 2013We have constructed a general theory describing the topological quantum phase transitions in 3D systems with broken inversion symmetry. While the consideration of the system's codimension generally predicts the appearance of a stable metallic phase between ... More
Geometrical indications of adsorbed hydrogen atoms on graphite producing starlike and ellipsoidal features in scanning tunneling microscopy imagesDec 08 2008Jan 24 2009Recent scanning tunneling spectroscopy (STM) experiments display images with star and ellipsoidal like features resulting from unique geometrical arrangements of a few adsorbed hydrogen atoms on graphite. Based on first-principles STM simulations, we ... More
A Computer Virus Propagation Model Using Delay Differential Equations With Probabilistic Contagion And ImmunityOct 21 2014The SIR model is used extensively in the field of epidemiology, in particular, for the analysis of communal diseases. One problem with SIR and other existing models is that they are tailored to random or Erdos type networks since they do not consider ... More
Superconductivity protected by spin-valley locking in ion-gated MoS2Jun 12 2015Jun 11 2016Symmetry-breaking has been known to play a key role in noncentrosymmetric superconductors with strong spin-orbit-interaction (SOI). The studies, however, have been so far mainly focused on a particular type of SOI, known as Rashba SOI, whereby the electron ... More
Kasner Solution in Brans-Dicke Theory and its Corresponding Reduced CosmologyMay 26 2014We present a brief review of the modified Brans-Dicke theory (MBDT) in arbitrary dimensions, whereby the ($N+1$)-dimensional field equations reduce to the $N$-dimensional $(ND)$ configuration with sources and an effective induced scalar potential. We ... More
The Dust Depletion and Extinction of the GRB 020813 AfterglowJun 02 2005The Keck optical spectrum of the GRB 020813 afterglow is the best ever obtained for GRBs. Its large spectral range and very high S/N ratio allowed for the first time the detection of a vast variety of absorption lines, associated with the circumburst ... More
Minimal SO(10) UnificationMay 20 1997Jul 16 1997It is shown that the doublet-triplet splitting problem can be solved in SO(10) using the Dimopoulos-Wilczek mechanism with a very economical Higgs content and simple structure. Only one adjoint Higgs field is required, together with spinor and vector ... More
Bootstrap quark model and spectra masses, electromagnetic properties of low-lying hadronsNov 22 2000The paper is devoted to the construction of low-energy quark scattering amplitudes. Bootstrap quark model allows to describe the light and heavy hadron spectroscopy based on three principles: unitarity, analicity and crossing symmetry. The resulting quark ... More
Theories relating baryon asymmetry and dark matter: A mini reviewOct 07 2013Dec 18 2013The nature of dark matter and the origin of the baryon asymmetry are two of the deepest mysteries of modern particle physics. In the absence of hints regarding a possible solution to these mysteries, many approaches have been developed to tackle them ... More
Scale free networks from a Hamiltonian dynamicsMay 03 2003Jul 09 2003Contrary to many recent models of growing networks, we present a model with fixed number of nodes and links, where it is introduced a dynamics favoring the formation of links between nodes with degree of connectivity as different as possible. By applying ... More
On the origin of variable gamma-ray emission from the Crab NebulaNov 08 2010Jan 31 2011The oblique geometry of pulsar wind termination shock ensures that the Doppler beaming has a strong impact on the shock emission. We illustrate this using recent relativistic MHD simulations of the Crab Nebula and also show that the observed size, shape, ... More
Anharmonic resonance absorption of short laser pulses in clusters: A molecular dynamics simulation studyDec 07 2016Linear resonance (LR) absorption of an intense 800~nm laser light in a nano-cluster requires a long laser pulse > 100~fs when Mie-plasma frequency ($\omegaMie$) of electrons in the expanding cluster matches the laser frequency~($\omega$). For a short ... More
Formation of internal shock waves in bent jetsSep 07 2001Jan 10 2002We discuss the circumstances under which the bending of a jet can generate an internal shock wave. The analysis is carried out for relativistic and non-relativistic astrophysical jets. The calculations are done by the method of characteristics for the ... More
Lift-and-project ranks of the stable set polytope of joined a-perfect graphsApr 29 2015In this paper we study lift-and-project polyhedral operators defined by Lov?asz and Schrijver and Balas, Ceria and Cornu?ejols on the clique relaxation of the stable set polytope of web graphs. We compute the disjunctive rank of all webs and consequently ... More
Tearing instability in relativistic magnetically dominated plasmasJun 15 2006Jun 21 2006Many astrophysical sources of high energy emission, such as black hole magnetospheres, superstrongly magnetized neutron stars (magnetars), and probably relativistic jets in Active Galactic Nuclei and Gamma Ray Bursts involve relativistically magnetically ... More
Configuration interaction approach to the few-body problem in a two-dimensional harmonic trap with contact interactionOct 23 2008The configuration interaction (CI) method for calculating the exact eigenstates of a quantum-mechanical few-body system is problematic when applied to contact interactions between the particles. In two and three dimensions, the approach fails due to the ... More
Characterizing multipartite symmetric Dicke states under the effects of noiseMar 23 2009Jun 26 2009We study genuine multipartite entanglement (GME) in a system of $n$ qubits prepared in symmetric Dicke states and subjected to the influences of noise. We provide general, setup-independent expressions for experimentally favorable tools such as fidelity- ... More
Quantum rings for beginners II: Bosons versus fermionsOct 02 2012The purpose of this overview article, which can be viewed as a supplement to our previous review on quantum rings, [S. Viefers {\it et al}, Physica E {\bf 21} (2004), 1-35], is to highlight the differences of boson and fermion systems in one-dimensional ... More
Generalized Induced NormsJul 21 2004Let ||.|| be a norm on the algebra M_n of all n-by-n matrices over the complex field C. An interesting problem in matrix theory is that "are there two norms ||.||_1 and ||.||_2 on C^n such that ||A||=max{||Ax||_2: ||x||_1=1} for all A in M_n. We will ... More
Relative Entropy and Tsallis Entropy of two Accretive OperatorsMay 19 2017Let $A$ and $B$ be two accretive operators. We first introduce the weighted geometric mean of $A$ and $B$ together with some related properties. Afterwards, we define the relative entropy as well as the Tsallis entropy of $A$ and $B$. The present definitions ... More
Magnetic phase diagrams in the H-T plane of the magnetically strongest sigma-phase Fe-V compoundsJul 14 2016Jul 15 2016Magnetization measurements were performed on two sigma-phase samples of Fe(100-x)V(x) (x=35.5, 34.1) vs. temperature, T, and in DC magnetic field, of various amplitudes. Using three characteristic temperatures, magnetic phase diagrams in the H-T plane ... More
A grid of Composite Models for the Simulation of Starburst Galaxy and HII Region SpectraJun 13 2001A grid of models for starburst spectra is presented and compared with power-law models which represent AGNs. The models are composite, i.e., they account for the radiation from the starburst and for the shocks created by super-winds. Some interesting ... More
Relativistic Kinetic Vertex in PositroniumFeb 24 2002Jan 19 2004We derive Spinless Salpeter equation for the positronium using the NRQED Lagrangian. Consequently, we consider the Spinless Salpeter wavefunction instead of the Schrodinger wavefunction to show that the NRQED calculation can be done easier. We also discuss ... More
Precision Cosmology and the Density of Baryons in the UniverseJul 31 2000Nov 14 2000Big-bang Nucleosynthesis (BBN) and Cosmic Microwave Background (CMB) anisotropy measurements give independent, accurate measurements of the baryon density and can test the framework of the standard cosmology. Early CMB data are consistent with the longstanding ... More
Inverse Compton scattering in mildly relativistic plasmaMar 30 1999We investigated the effect of inverse Compton scattering in mildly relativistic static and moving plasmas with low optical depth using Monte Carlo simulations, and calculated the Sunyaev-Zel'dovich effect in the cosmic background radiation. Our semi-analytic ... More
Stability of Derivations on Hilbert $C^*$-ModulesMar 21 2006Consider the functional equation ${\mathcal E}_1(f) = {\mathcal E}_2(f) ({\mathcal E})$ in a certain framework. We say a function $f_0$ is an approximate solution of $({\mathcal E})$ if ${\mathcal E}_1(f_0)$ and ${\mathcal E}_2(f_0)$ are close in some ... More
Operator convexity in Krein spacesJan 14 2014We introduce the notion of Krein-operator convexity in the setting of Krein spaces. We present an indefinite version of the Jensen operator inequality on Krein spaces by showing that if $(\mathscr{H},J)$ is a Krein space, $\mathcal{U}$ is an open set ... More
Investigation of quantum rouletteJul 20 2008Apr 30 2009In this paper, by using permutation matrices as a representation of symmetric group $S_N$ and Fourier matrix, we investigate quantum roulette with an arbitrary $N$-state. This strategy, which we introduce, is general method that allows us to solve quantum ... More
The gas distribution in the high-redshift cluster MS 1054-0321Jan 20 2016We investigate the gas mass distribution in the high redshift cluster MS 1054-0321 using Chandra X-ray and OCRA SZ effect data. We use a superposition of offset $\beta$-type models to describe the composite structure of MS 1054-0321. We find gas mass ... More
A grid of composite models for the simulation of the emission-line spectra from the NLR of active galaxiesSep 06 2000A grid of composite models for the narrow line region of active galaxies, which consistently account for both the effect of a photoionizing radiation from the active center and of a shock front, is presented. Theoretical results, calculated with the SUMA ... More
CFT Duals for Ultra-Spinning Gauged Supergravity Black HolesNov 07 2016Recently a new class of asymptotically AdS ultra-spinning black holes has been constructed with non-compact horizon of finite area [1], in which the asymptotic rotation is effectively boosted to the speed of light. We employ this technique to the $4$-dimensional ... More
Khintchine's theorem and transference principle for star bodiesJan 12 2006Analogues of Khintchine's Theorem in simultaneous Diophantine approximation in the plane are proved with the classical height replaced by fairly general planar distance functions or equivalently star bodies. Khintchine's transference principle is discussed ... More
Electron correlation in metal clusters, quantum dots and quantum ringsOct 15 2008This short review presents a few case studies of finite electron systems for which strong correlations play a dominant role. In simple metal clusters, the valence electrons determine stability and shape of the clusters. The ionic skeleton of alkali metals ... More
Metal clusters, quantum dots and trapped atoms -- from single-particle models to correlatioMar 12 2007In this review, we discuss the electronic structure of finite quantal systems on the nanoscale. After a few general remarks on the many-particle physics of the harmonic oscillator -- likely being the most studied example for the many-body systems of finite ... More
Orthogonal Constant Mappings in Isosceles Orthogonal SpacesApr 21 2006In this paper we introduce the notion of orthogonally constant mapping in an isosceles orthogonal space and establish stability of orthogonally constant mappings. As an application, we discuss the orthogonal stability of the Pexiderized quadratic equation ... More
Approximate Homomorphisms of Ternary SemigroupsNov 10 2005A mapping $f:(G_1,[ ]_1)\to (G_2,[ ]_2)$ between ternary semigroups will be called a ternary homomorphism if $f([xyz]_1)=[f(x)f(y)f(z)]_2$. In this paper, we prove the generalized Hyers--Ulam--Rassias stability of mappings of commutative semigroups into ... More
$(σ,τ)$-amenability of $C^*$-algebrasNov 14 2009Suppose that ${\mathcal A}$ is an algebra, $\sigma,\tau:{\mathcal A}\to{\mathcal A}$ are two linear mappings such that both $\sigma({\mathcal A})$ and $\tau({\mathcal A})$ are subalgebras of ${\mathcal A}$ and ${\mathcal X}$ is a $\big(\tau({\mathcal ... More
A Kadison-Sakai Type TheoremOct 13 2005Jan 07 2008The celebrated Kadison--Sakai theorem states that every derivation on a von Neumann algebra is inner. In this paper, we prove this theorem for ultraweakly continuous *-\sigma-derivations, where \sigma is an ultraweakly continuous surjective *-linear mapping. ... More
On the effect of the thermal gas component to the stability of vortices in trapped Bose-Einstein condensatesMar 12 2002We study the stability of vortices in trapped single-component Bose-Einstein condensates within self-consistent mean-field theories--especially we consider the Hartree-Fock-Bogoliubov-Popov theory and its recently proposed gapless extensions. It is shown ... More
On charge and spin ordering in a one-dimensional model with frustrating interactionsOct 01 2005Oct 06 2005We study a one-dimensional extended Hubbard model with longer-range Coulomb interactions at quarter-filling in the strong coupling limit. We find two different charge-ordered ground states as the strength of the longer range interactions is varied. At ... More
Deflection of Jets Induced by Jet-Cloud InteractionsApr 02 2001A non--relativistic and relativistic model in which astrophysical jets are deflected on passing through an isothermal high density region is analysed. The criteria for the stability of jets due to the formation of internal shocks are discussed.
Chandra View of the Dynamically Young Cluster of Galaxies A1367 I. Small-Scale StructuresJun 14 2002The 40 ks \emph{Chandra} ACIS-S observation of A1367 provides new insights into small-scale structures and point sources in this dynamically young cluster. Here we concentrate on small-scale extended structures. A ridge-like structure around the center ... More
Redshift drift in an inhomogeneous universe: averaging and the backreaction conjectureDec 17 2015Jan 09 2016An expression for the average redshift drift in a statistically homogeneous and isotropic dust universe is given. The expression takes the same form as the expression for the redshift drift in FLRW models. It is used for a proof-of-principle study of ... More
Chandra view of the dynamically young cluster of galaxies A1367 II. point sourcesFeb 22 2002Jun 14 2002A 40 ks \emph{Chandra} ACIS-S observation of the dynamically young cluster A1367 yields new insights on X-ray emission from cluster member galaxies. We detect 59 point-like sources in the ACIS field, of which 8 are identified with known cluster member ... More
Plasmon exchange model for superconductivity in Carbon nanotubesFeb 20 2004Recent investigations of superconductivity in carbon nanotubes have shown that a single-wall zigzag nanotube can become superconducting at around 15 K. Theoretical studies of superconductivity in nanotubes using the traditional phonon exchange model, ... More
Methods for studying the accuracy of light propagation in N-body simulationsJan 07 2015Aug 15 2015It is proposed to use exact, cosmologically relevant solutions to Einstein's equations to accurately quantify the precision of ray tracing techniques through Newtonian N-body simulations. As an initial example of such a study, the recipe in (Green & Wald, ... More
Studying the precision of ray tracing techniques with Szekeres modelsJun 30 2015Oct 02 2015The simplest standard ray tracing scheme employing the Born and Limber approximations and neglecting lens-lens coupling is used for computing the convergence along individual rays in mock N-body data based on Szekeres swiss cheese and onion models. The ... More
Deflection of jets induced by jet-cloud & jet-galaxy interactionsAug 01 2000Mar 31 2001The model first introduced by Raga & Canto (1996) in which astrophysical jets are deflected on passing through an isothermal high density region is generalised by taking into account gravitational effects on the motion of the jet as it crosses the high ... More
On the formation of Wigner molecules in small quantum dotsApr 06 2000It was recently argued that in small quantum dots the electrons could crystallize at much higher densities than in the infinite two-dimensional electron gas. We compare predictions that the onset of spin polarization and the formation of Wigner molecules ... More
Quasi-representations of Finsler modules over C*-algebrasJan 01 2012Jan 12 2012We show that every Finsler module over a $C^*$-algebra has a quasi-representation into the Banach space $\mathbb{B}(\mathscr{H},\mathscr{K})$ of all bounded linear operators between some Hilbert spaces $\mathscr{H}$ and $\mathscr{K}$. We define the notion ... More
The 2D analogue of the Reissner-Nordstrom solutionSep 09 1996A two-dimensional (2D) dilaton gravity model, whose static solutions have the same features of the Reissner-Nordstrom solutions, is obtained from the dimensional reduction of a four-dimensional (4D) string effective action invariant under S-duality transformations. ... More
Classical and Semiclassical Properties of Extremal Black Holes with Dilaton and Modulus FieldsDec 21 1993Jan 28 1994We discuss both classical and semiclassical properties of extremal black holes in theories where the dilaton and a modulus field are present. We find that the corresponding 2-dim geometry is asymptotically anti-de Sitter rather then asymptotically flat ... More
Minimal $R+R^2$ Supergravity Models of Inflation Coupled to MatterJul 23 2014The supersymmetric extension of "Starobinsky" $R+\alpha R^2$ models of inflation is particularly simple in the "new minimal" formalism of supergravity, where the inflaton has no scalar superpartners. This paper is devoted to matter couplings in such supergravity ... More
AdS Superalgebras with Brane ChargesMar 29 1999Apr 13 1999We consider the inclusion of brane charges in AdS_5 superalgebras that contain the maximal central extension of the super-Poincar\'e algebra on the boundary of AdS_5. For theories with N supersymmetries on the boundary, the maximal extension is OSp(1/8N,R), ... More
N=1 No-Scale Supergravity from IIB OrientifoldsJul 13 2002Sep 03 2002We describe the low-energy effective theory of N=1 spontaneously broken supegravity obtained by flux-induced breaking in the presence of n D3 branes. This theory can be obtained by integrating out three massive gravitino multiplets in the hierarchical ... More
Quantization of mental stress using various physiological markersFeb 05 2015May 01 2015The aim of this study is to quantize mental stress by integrating different physiological markers like reaction time, photoplethysmograph (PPG), heart rate variability (HRV) and subjective markers like questionnaire. The study included 10 subjects of ... More
Measurement of the differential surface and volume excitation probability of medium energy electrons in solidsMar 18 2005A procedure is developed to rigorously decompose experimental loss spectra of medium-energy electrons reflected from solid surfaces into contributions due to surface and volume electronic excitations. This can be achieved by analysis of two spectra acquired ... More
Theoretical description of field-assisted post-collision interaction in Auger decay of atomsMar 21 2012Apr 24 2012In a recent publication [B. Schuette, S. Bauch et al., accepted for publication in Phys. Rev. Lett. 2012] it was demonstrated both, experimentally and theoretically, that Auger electrons are subject to an energetic chirp if a three-body-interaction dubbed ... More
Two states hydrogenlike model for High-Order Harmonic Generation and enhanced XUV Generation from a coherent superposition of bound statesApr 17 2011We present an analytic, and fully quantum theory of high harmonic generation by low frequency laser fields for a two-state hydrogenlike atom model. The model is valid for an arbitrary atomic potential role of dipole matrix elements and can be generalized ... More
Superbubble Activity in Star-Forming GalaxiesDec 03 2002Mechanical feedback from massive stars, primarily from supernovae, can dominate ISM structuring and phase balance, thereby profoundly affecting galactic evolutionary processes. Our understanding of mechanical feedback is based on the adiabatic, wind-driven ... More
HI as a Probe of Structure in the Interstellar Medium of External GalaxiesDec 10 2001This review presents a perspective on recent advances in understanding neutral ISM structure in external galaxies. HI is a fundamental probe of galactic baryonic material, and its structure and distribution offer vital signatures of dynamical and evolutionary ... More
A New Look at Simple Inhomogeneous Chemical EvolutionAug 18 2000Sep 29 2000A rudimentary, one-zone, closed-box model for inhomogeneous chemical evolution is offered as an alternative reference than the Simple model in the limit of no mixing. The metallicity distribution functions (MDFs) of Galactic halo and bulge stars can be ... More
Comment on "Brown Dwarfs, Quark Stars, and Quark-Hadron Phase Transition"Mar 23 1996Recently, Cottingham, Kalafatis and Vinh Mau proposed, in the framework of the Lee-Wick model, a scenario of formation of quark stars in the cosmological quark-hadron phase transition with high degree of supercooling. We show here that the cosmological ... More
Thermodynamical properties of QED in 1+1 dimensions within light front dynamicsOct 29 2008We investigate thermodynamical properties of quantum electrodynamics in 1+1 dimensions. Discrete light cone quantization is used to compute the partition function of the canonical ensemble and the thermodynamical potential. The potential is evaluated ... More
Observable (?) cosmological signatures of superstrings in pre-big bang models of inflationNov 03 2005Dec 20 2005The different couplings of the dilaton to the U(1) gauge field of heterotic and Type I superstrings may leave an imprint on the relics of the very early cosmological evolution. Working in the context of the pre-big bang scenario, we discuss the possibility ... More
Cool core remnants in galaxy clustersOct 26 2009X ray clusters are conventionally divided into two classes: "cool core" (CC) and "non cool core" (NCC) objects, on the basis of the observational properties of their central regions. Recent results have shown that the cluster population is bimodal (Cavagnolo ... More
$ψ$-epistemic models are exponentially bad at explaining the distinguishability of quantum statesJan 30 2014Apr 19 2014The status of the quantum state is perhaps the most controversial issue in the foundations of quantum theory. Is it an epistemic state (state of knowledge) or an ontic state (state of reality)? In realist models of quantum theory, the epistemic view asserts ... More