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Full-Text Articles in Physics

Phase Transitions In Mgsio3 Post-Perovskite In Super-Earth Mantles, Koichiro Umemoto, Renata M. Wentzcovitch, Shunqing Wu, Min Ji, Cai-Zhuang Wang, Kai-Ming Ho Nov 2017

Phase Transitions In Mgsio3 Post-Perovskite In Super-Earth Mantles, Koichiro Umemoto, Renata M. Wentzcovitch, Shunqing Wu, Min Ji, Cai-Zhuang Wang, Kai-Ming Ho

Ames Laboratory Accepted Manuscripts

The highest pressure form of the major Earth-forming mantle silicate is MgSiO3 post-perovskite (PPv). Understanding the fate of PPv at TPa pressures is the first step for understanding the mineralogy of super-Earths-type exoplanets, arguably the most interesting for their similarities with Earth. Modeling their internal structure requires knowledge of stable mineral phases, their properties under compression, and major element abundances. Several studies of PPv under extreme pressures support the notion that a sequence of pressure induced dissociation transitions produce the elementary oxides SiO2 and MgO as the ultimate aggregation form at ∼3 TPa. However, none of these studies have addressed ...


Adsorption And Diffusion Of Ru Adatoms On Ru(0001)-Supported Graphene: Large-Scale First-Principles Calculations, Yong Han, James W. Evans Oct 2015

Adsorption And Diffusion Of Ru Adatoms On Ru(0001)-Supported Graphene: Large-Scale First-Principles Calculations, Yong Han, James W. Evans

Physics and Astronomy Publications

Large-scale first-principles density functional theory calculations are performed to investigate the adsorption and diffusion of Ru adatoms on monolayer graphene (G) supported on Ru(0001). The G sheet exhibits a periodic moiré-cell superstructure due to lattice mismatch. Within a moirécell, there are three distinct regions: fcc, hcp, and mound, in which the C6-ring center is above a fcc site, a hcp site, and a surface Ru atom of Ru(0001), respectively. The adsorption energy of a Ru adatom is evaluated at specific sites in these distinct regions. We find the strongest binding at an adsorption site above a C atom ...


Refined Bcf-Type Boundary Conditions For Mesoscale Surface Step Dynamics, Renjie Zhao, David M. Ackerman, James W. Evans Jun 2015

Refined Bcf-Type Boundary Conditions For Mesoscale Surface Step Dynamics, Renjie Zhao, David M. Ackerman, James W. Evans

Physics and Astronomy Publications

Deposition on a vicinal surface with alternating rough and smooth steps is described by a solid-on-solid model with anisotropic interactions. Kinetic Monte Carlo (KMC) simulations of the model reveal step pairing in the absence of any additional step attachment barriers. We explore the description of this behavior within an analytic Burton-Cabrera-Frank (BCF)-type step dynamics treatment. Without attachment barriers, conventional kinetic coefficients for the rough and smooth steps are identical, as are the predicted step velocities for a vicinal surface with equal terrace widths. However, we determine refined kinetic coefficients from a two-dimensional discrete deposition-diffusion equation formalism which accounts for ...


Kinetic Monte Carlo Simulation Of Statistical Mechanical Models And Coarse-Grained Mesoscale Descriptions Of Catalytic Reaction–Diffusion Processes: 1d Nanoporous And 2d Surface Systems, Da-Jiang Liu, Andrés Garcia, Jing Wang, David M. Ackerman, Chi-Jen Wang, James W. Evans Apr 2015

Kinetic Monte Carlo Simulation Of Statistical Mechanical Models And Coarse-Grained Mesoscale Descriptions Of Catalytic Reaction–Diffusion Processes: 1d Nanoporous And 2d Surface Systems, Da-Jiang Liu, Andrés Garcia, Jing Wang, David M. Ackerman, Chi-Jen Wang, James W. Evans

Physics and Astronomy Publications

Traditional mean-field rate equations of chemical kinetics for spatially uniform systems1−3 and the corresponding reaction−diffusion equations describing spatial heterogeneity4−6 have proved immensely useful in elucidating catalytic processes. However, it is well-recognized that standard mean-field rate expressions neglect spatial correlations in the reactant and/or product distribution. It is less well appreciated that the standard treatment of diffusion is generally applicable only at low concentrations and in unrestricted environments.


Discontinuous Non-Equilibrium Phase Transition In A Threshold Schloegl Model For Autocatalysis: Generic Two-Phase Coexistence And Metastability, Chi-Jen Wang, Da-Jiang Liu, James W. Evans Apr 2015

Discontinuous Non-Equilibrium Phase Transition In A Threshold Schloegl Model For Autocatalysis: Generic Two-Phase Coexistence And Metastability, Chi-Jen Wang, Da-Jiang Liu, James W. Evans

Physics and Astronomy Publications

Threshold versions of Schloegl's model on a lattice, which involve autocatalytic creation and spontaneous annihilation of particles, can provide a simple prototype for discontinuous non-equilibrium phase transitions. These models are equivalent to so-called threshold contact processes. A discontinuous transition between populated and vacuum states can occur selecting a threshold of N ≥ 2 for the minimum number, N, of neighboring particles enabling autocatalytic creation at an empty site. Fundamental open questions remain given the lack of a thermodynamic framework for analysis. For a square lattice with N = 2, we show that phase coexistence occurs not at a unique value but ...


Transitions Between Strongly Correlated And Random Steady-States For Catalytic Co-Oxidation On Surfaces At High-Pressure, Da-Jiang Liu, James W. Evans Apr 2015

Transitions Between Strongly Correlated And Random Steady-States For Catalytic Co-Oxidation On Surfaces At High-Pressure, Da-Jiang Liu, James W. Evans

Physics and Astronomy Publications

We explore simple lattice-gas reaction models for CO-oxidation on 1D and 2D periodic arrays of surface adsorption sites with CO adsorption and desorption, dissociative O2 adsorption and recombinative desorption (at low rate), and CO + O reaction to form CO2. Adspecies interactions are neglected, and adspecies diffusion is effectively absent. The models are motivated by studies of CO-oxidation on RuO2(110) at high-pressures. Despite the lack of adspecies interactions, negligible adspecies diffusion results in kinetically induced spatial correlations. A transition occurs from a random primarily CO-populated steady-state at high CO-partial pressure, pCO, to a strongly correlated near-O-covered steady-state for low pCO ...


Synchrotron Radiation Of Vector Bosons At Relativistic Colliders, Kirill Tuchin Jan 2015

Synchrotron Radiation Of Vector Bosons At Relativistic Colliders, Kirill Tuchin

Physics and Astronomy Publications

Magnetic fields produced in collisions of electrically charged particles at relativistic energies are strong enough to affect the dynamics of the strong interactions. In particular, it induces radiation of vector bosons by relativistic fermions. I calculate the corresponding spectrum in constant magnetic field and analyze its angular distribution and mass dependence. As an application, synchrotron radiation of vector bosons by relativistic plasmas is considered.


Role Of Magnetic Field In Photon Excess In Heavy Ion Collisions, Kirill Tuchin Jan 2015

Role Of Magnetic Field In Photon Excess In Heavy Ion Collisions, Kirill Tuchin

Physics and Astronomy Publications

The synchrotron photon spectrum in heavy ion collisions is computed taking into account the spatial and temporal structure of the magnetic field. It is found that a significant fraction of photon excess in heavy ion collisions in the region k⊥ = 1–3 GeV can be attributed to the synchrotron radiation. Azimuthal anisotropy of the synchrotron photon spectrum is characterized by the Fourier coefficients v2 = 4/7 and v4 = 1/10 that are independent of photon momentum and centrality.


Electromagnetic Field And The Chiral Magnetic Effect In The Quark-Gluon Plasma, Kirill Tuchin Jan 2015

Electromagnetic Field And The Chiral Magnetic Effect In The Quark-Gluon Plasma, Kirill Tuchin

Physics and Astronomy Publications

Time evolution of an electromagnetic field created in heavy-ion collisions strongly depends on the electromagnetic response of the quark-gluon plasma, which can be described by the Ohmic and chiral conductivities. The latter is intimately related to the chiral magnetic effect. I argue that a solution to the classical Maxwell equations at finite chiral conductivity is unstable due to the soft modes k < σχ that grow exponentially with time. In the kinematical region relevant for the relativistic heavy-ion collisions, I derive analytical expressions for the magnetic field of a point charge. I show that finite chiral conductivity causes oscillations of magnetic field at early times.


Reconstruction Of Steps On The Cu(111) Surface Induced By Sulfur, Holly L. Walen, Da-Jiang Liu, Junepyo Oh, Hyunseob Lim, James W. Evans, Yousoo Kim, Patricia A. Thiel Jan 2015

Reconstruction Of Steps On The Cu(111) Surface Induced By Sulfur, Holly L. Walen, Da-Jiang Liu, Junepyo Oh, Hyunseob Lim, James W. Evans, Yousoo Kim, Patricia A. Thiel

Chemistry Publications

Arich menagerie of structures is identified at 5Kfollowing adsorption of lowcoverages (≤0.05 monolayers) of S on Cu(111) at room temperature. This paper emphasizes the reconstructions at the steps. The A-type close-packed step has 1 row of S atoms along its lower edge, where S atoms occupy alternating pseudo-fourfold-hollow (p4fh) sites. Additionally, there are 2 rows of S atoms of equal density on the upper edge, bridging a row of extra Cu atoms, together creating an extended chain. The B-type close-packed step exhibits an even more complex reconstruction, in which triangle-shaped groups of Cu atoms shift out of their ...


Cu2s3 Complex On Cu(111) As A Candidate For Mass Transport Enhancement, Holly L. Walen, Da-Jiang Liu, Junepyo Oh, Hyunseob Lim, James W. Evans, Christine M. Aikens, Yousoo Kim, Patricia A. Thiel Jan 2015

Cu2s3 Complex On Cu(111) As A Candidate For Mass Transport Enhancement, Holly L. Walen, Da-Jiang Liu, Junepyo Oh, Hyunseob Lim, James W. Evans, Christine M. Aikens, Yousoo Kim, Patricia A. Thiel

Chemistry Publications

Sulfur-metal complexes, containing only a few atoms, can open new, highly efficient pathways for transport of metal atoms on surfaces. For example, they can accelerate changes in the shape and size of morphological features, such as two-dimensional nanoclusters, over time. In this study we perform STM under conditions that are designed to specifically isolate such complexes. We find a new, unexpected S-Cu complex on the Cu(111) surface, which we identify as Cu2S3. We propose that Cu2S3 enhances mass transport in this system, which contradicts a previous proposal based on Cu3S3 ...


Nonclassical “Explosive” Nucleation In Pb/Si(111) At Low Temperatures, Matthew T. Hershberger, Myron Hupalo, Patricia A. Thiel, Cai-Zhuang Wang, Kai-Ming Ho, Michael C. Tringides Dec 2014

Nonclassical “Explosive” Nucleation In Pb/Si(111) At Low Temperatures, Matthew T. Hershberger, Myron Hupalo, Patricia A. Thiel, Cai-Zhuang Wang, Kai-Ming Ho, Michael C. Tringides

Chemistry Publications

Classically, the onset of nucleation is defined in terms of a critical cluster of the condensed phase, which forms from the gradual aggregation of randomly diffusing adatoms. Experiments in Pb/Si(111) at low temperature have discovered a dramatically different type of nucleation, with perfect crystalline islands emerging “explosively” out of the compressed wetting layer after a critical coverage Θc ¼ 1.22 ML is reached. The unexpectedly high island growth rates, the directional correlations in the growth of neighboring islands and the persistence in time of where mass is added in individual islands, suggest that nucleation is a result ...


Real-Time Ab Initio Kmc Simulation Of The Self-Assembly And Sintering Of Bimetallic Epitaxial Nanoclusters: Au + Ag On Ag(100), Yong Han, Da-Jiang Liu, James W. Evans Jun 2014

Real-Time Ab Initio Kmc Simulation Of The Self-Assembly And Sintering Of Bimetallic Epitaxial Nanoclusters: Au + Ag On Ag(100), Yong Han, Da-Jiang Liu, James W. Evans

Physics and Astronomy Publications

Far-from-equilibrium shape and structure evolution during formation and post-assembly sintering of bimetallic nanoclusters is extremely sensitive to the periphery diffusion and intermixing kinetics. Precise characterization of the many distinct local-environment-dependent diffusion barriers is achieved for epitaxial nanoclusters using density functional theory to assess interaction energies both with atoms at adsorption sites and at transition states. Kinetic Monte Carlo simulation incorporating these barriers then captures structure evolution on the appropriate time scale for two-dimensional core-ring and intermixed Au–Ag nanoclusters on Ag(100).


Dissociative Adsorption Of O2 On Unreconstructed Metal (100) Surfaces: Pathways, Energetics, And Sticking Kinetics, Da-Jiang Liu, James W. Evans May 2014

Dissociative Adsorption Of O2 On Unreconstructed Metal (100) Surfaces: Pathways, Energetics, And Sticking Kinetics, Da-Jiang Liu, James W. Evans

Physics and Astronomy Publications

An accurate description of oxygen dissociation pathways and kinetics for various local adlayer environments is key for an understanding not just of the coverage dependence of oxygen sticking, but also of reactive steady states in oxidation reactions. Density functional theory analysis for M(100) surfaces with M=Pd, Rh, and Ni, where O prefers the fourfold hollow adsorption site, does not support the traditional Brundle-Behm-Barker picture of dissociative adsorption onto second-nearest-neighbor hollow sites with an additional blocking constraint. Rather adsorption via neighboring vicinal bridge sites dominates, although other pathways can be active. The same conclusion also applies for M=Pt ...


Statistical Mechanical Models For Dissociative Adsorption Of O2 On Metal(100) Surfaces With Blocking, Steering, And Funneling, Da-Jiang Liu, James W. Evans May 2014

Statistical Mechanical Models For Dissociative Adsorption Of O2 On Metal(100) Surfaces With Blocking, Steering, And Funneling, Da-Jiang Liu, James W. Evans

Physics and Astronomy Publications

We develop statistical mechanical models amenable to analytic treatment for the dissociative adsorption of O2 at hollow sites on fcc(100) metal surfaces. The models incorporate exclusion of nearest-neighbor pairs of adsorbed O. However, corresponding simple site-blocking models, where adsorption requires a large ensemble of available sites, exhibit an anomalously fast initial decrease in sticking. Thus, in addition to blocking, our models also incorporate more facile adsorption via orientational steering and funneling dynamics (features supported by ab initio Molecular Dynamics studies). Behavior for equilibrated adlayers is distinct from those with finite adspecies mobility. We focus on the low-temperature limited-mobility regime ...


Violation Of Geometric Scaling In Deep Inelastic Scattering Due To Coulomb Corrections, Kirill Tuchin Feb 2014

Violation Of Geometric Scaling In Deep Inelastic Scattering Due To Coulomb Corrections, Kirill Tuchin

Physics and Astronomy Publications

We compute the Coulomb correction to the total and diffractive cross sections for virtual photon scattering off a heavy nucleus at low x. We show that it violates the geometric scaling in a wide range of photon virtualities and is weakly x independent. In heavy nuclei at low Q2, the Coulomb correction to the total and diffractive cross sections is about 20% and 40%, correspondingly.


Coulomb Corrections To Photon And Dilepton Production In High-Energy P A Collisions, Kirill Tuchin Jan 2014

Coulomb Corrections To Photon And Dilepton Production In High-Energy P A Collisions, Kirill Tuchin

Physics and Astronomy Publications

I consider particle production in high-energy pA collisions. In addition to the coherent interactions with the nuclear color field, I take into account coherent interactions with the nuclear electromagnetic Coulomb field. Employing the dipole model, I sum up the leading multiple color and electromagnetic interactions and derive inclusive cross sections for photon and dilepton production. I found that the Coulomb corrections are up to 10% at √ s = 200 GeV per nucleon.


Nuclear Modification Of The J/Psi Transverse Momentum, Dmitri Kharzeev, Eugene M. Levin, Kirill Tuchin Jan 2014

Nuclear Modification Of The J/Psi Transverse Momentum, Dmitri Kharzeev, Eugene M. Levin, Kirill Tuchin

Physics and Astronomy Publications

We evaluate the transverse momentum spectrum of J/ψ (up to semi-hard momenta) in pA and AA collisions taking into account only the initial state effects, but resumming them to all orders in αs2A1/3. In our previous papers we noticed that cold nuclear matter effects alone could not explain the experimental data on rapidity and centrality dependencies of the J/ψ yield in AA collisions indicating the existence of an additional suppression mechanism. Our present calculations indicate that the discrepancy persists and even increases at semi-hard transverse momenta, implying a significant final state effect on J/ψ production ...


Search For The Structure Of A Sulfur-Induced Reconstruction On Cu(111), Da-Jiang Liu, Holly L. Walen, Junepyo Oh, James W. Evans, Yousoo Kim, Patricia A. Thiel Jan 2014

Search For The Structure Of A Sulfur-Induced Reconstruction On Cu(111), Da-Jiang Liu, Holly L. Walen, Junepyo Oh, James W. Evans, Yousoo Kim, Patricia A. Thiel

Chemistry Publications

We have carried out an extensive DFT-based search for the structure of the (√43 × √43)R ± 7.5° reconstruction of S on Cu(111), which exhibits a honeycombtype structure in scanning tunneling microscopy (STM). We apply two criteria in this search: The structure must have a reasonably low chemical potential, and it must provide a good match with STM data, both our own and the data published by Wahlström et al. Phys. Rev. B 1999, 60, 10699. The best model has 12 S adatoms and 9 Cu adatoms per unit cell. Local defects within the Cu9S12 framework, consisting of ...


Taking Advantage Of Gold’S Electronegativity In R4mn3–Xau10+X (R = Gd Or Y; 0.2 ≤ X ≤ 1), Saroj L. Samal, Abhishek Pandey, D. C. Johnston, John D. Corbett, Gordon J. Miller Jan 2014

Taking Advantage Of Gold’S Electronegativity In R4mn3–Xau10+X (R = Gd Or Y; 0.2 ≤ X ≤ 1), Saroj L. Samal, Abhishek Pandey, D. C. Johnston, John D. Corbett, Gordon J. Miller

Chemistry Publications

Ternary R4Mn3–xAu10+x (R = Gd or Y; 0.2 ≤ x ≤ 1) compounds have been synthesized and characterized using single-crystal X-ray diffraction. The structure is a ternary variant of orthorhombic Zr7Ni10 (oC68, space group Cmca) and is isostructural with Ca4In3Au10. The structure contains layers of Mn-centered rectangular prisms of gold (Mn@Au8), interbonded via Au atoms in the b-c plane, and stacked in a hexagonal close packed arrangement along the a direction. These layers are bonded via additional Mn atoms along the a direction. The ...


Beyond The Proton Collinear Factorization In Heavy Quark Production In Pa Collisions At Low X, Kirill Tuchin Jan 2013

Beyond The Proton Collinear Factorization In Heavy Quark Production In Pa Collisions At Low X, Kirill Tuchin

Physics and Astronomy Publications

We consider heavy quark production in high energy pA collisions and investigate the contribution of interactions of valence quarks of proton with the nucleus. The often made assumption that valence quarks of proton can be factored out is justified only if the nucleus saturation momentum is much smaller than the heavy quark mass. This is not the case in phenomenologically relevant situations. Breakdown of factorization manifests itself in substantial decrease of the cross section at large total and small relative transverse momenta of the heavy quark-antiquark pair.


Particle Production In Strong Electromagnetic Fields In Relativistic Heavy-Ion Collisions, Kirill Tuchin Jan 2013

Particle Production In Strong Electromagnetic Fields In Relativistic Heavy-Ion Collisions, Kirill Tuchin

Physics and Astronomy Publications

I review the origin and properties of electromagnetic fields produced in heavy-ion collisions. The field strength immediately after a collision is proportional to the collision energy and reaches mπ2 at RHIC and 10mπ2 at LHC. I demonstrate by explicit analytical calculation that after dropping by about one-two orders of magnitude during the first fm/c of plasma expansion, it freezes out and lasts for as long as quark-gluon plasma lives as a consequence of finite electrical conductivity of the plasma. Magnetic field breaks spherical symmetry in the direction perpendicular to the reaction plane, and therefore all kinetic coefficients ...


Magnetic Contribution To Dilepton Production In Heavy-Ion Collisions, Kirill Tuchin Jan 2013

Magnetic Contribution To Dilepton Production In Heavy-Ion Collisions, Kirill Tuchin

Physics and Astronomy Publications

We calculate a novel "magnetic contribution" to the dilepton spectrum in heavy-ion collisions arising from interaction of relativistic quarks with intense magnetic field. Synchrotron radiation by quarks, which can be approximated by the equivalent photon flux, is followed by dilepton decay of photons in an intense magnetic field. We argue that the "magnetic contribution" dominates the dilepton spectrum at low lepton energies, whereas a conventional photon dilepton decay dominates at higher lepton energies.


Electromagnetic Radiation By Quark-Gluon Plasma In A Magnetic Field, Kirill Tuchin Jan 2013

Electromagnetic Radiation By Quark-Gluon Plasma In A Magnetic Field, Kirill Tuchin

Physics and Astronomy Publications

The electromagnetic radiation by quark-gluon plasma in a strong magnetic field is calculated. The contributing processes are synchrotron radiation and one-photon annihilation. It is shown that in relativistic heavy-ion collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC) synchrotron radiation dominates over the annihilation. Moreover, it constitutes a significant part of all photons produced by the plasma at low transverse momenta; its magnitude depends on the plasma temperature and the magnetic field strength. Electromagnetic radiation in a magnetic field is probably the missing piece that resolves a discrepancy between the theoretical models and the ...


Time And Space Dependence Of The Electromagnetic Field In Relativistic Heavy-Ion Collisions, Kirill Tuchin Jan 2013

Time And Space Dependence Of The Electromagnetic Field In Relativistic Heavy-Ion Collisions, Kirill Tuchin

Physics and Astronomy Publications

Exact analytical solution for the space-time evolution of electromagnetic field in electrically conducting nuclear matter produced in heavy-ion collisions is discussed. It is argued that the parameter that controls the strength of the matter effect on the field evolution is σγb, where σ is electrical conductivity, γ is the Lorentz boost-factor, and b is the characteristic transverse size of the matter. When this parameter is of the order 1 or larger, which is the case at the Relativistic Heavy Ion Collider and the Large Hadron Collider, the space-time dependence of the electromagnetic field completely differs from that in vacuum.


The Vhe Gamma-Ray Spectra Of Several Hard-Spectrum Blazars From Long-Term Observations With The Veritas Telescope Array, Arun Sreenivasan Madhavan Jan 2013

The Vhe Gamma-Ray Spectra Of Several Hard-Spectrum Blazars From Long-Term Observations With The Veritas Telescope Array, Arun Sreenivasan Madhavan

Graduate Theses and Dissertations

Analysis is presented on VERITAS observations of the very high energy gamma-ray spectra of five high frequency peaked BL Lac objects over a range of redshifts. Each object has an unusually hard intrinsic GeV spectrum, and is expected to produce TeV gamma-ray emission into the optically- thick regime of the universe's diffuse extragalactic background light (EBL). Hard spectrum HBLs have recently emerged as an effective tool for measurement of the EBL spectrum, due to extinction of gamma-ray signals from blazars via the pair production interaction gamma-TeV gamma-EBL → e+e−. The VERITAS collaboration has approved long term observations on several ...


Analytic Formulations For One-Dimensional Decay Of Rectangular Homoepitaxial Islands During Coarsening On Anisotropic Fcc (110) Surfaces, Chi-Jen Wang, Yong Han, Holly L. Walen, Selena M. Russell, Patricia A. Thiel, James W. Evans Jan 2013

Analytic Formulations For One-Dimensional Decay Of Rectangular Homoepitaxial Islands During Coarsening On Anisotropic Fcc (110) Surfaces, Chi-Jen Wang, Yong Han, Holly L. Walen, Selena M. Russell, Patricia A. Thiel, James W. Evans

Chemistry Publications

Submonolayer homoepitaxial fcc (110) systems display behavior reflecting strong anisotropy at lower temperatures, including one-dimensional decay during Ostwald ripening of rectangular islands maintaining constant width in the 〈001〉 direction. To appropriately describe this behavior, we first develop a refined continuum Burton-Cabrera-Frank formalism, which accounts for a lack of equilibration of island shape and importantly also for inhibited incorporation of adatoms at almost-faceted 〈1̄10〉 island edges through effective kinetic coefficients. This formalism is shown to describe accurately the adatom diffusion fluxes between islands and thus island evolution for a complex experimental island configuration, as confirmed by matching results ...


Tricriticality In Generalized Schloegl Models For Autocatalysis: Lattice-Gas Realization With Particle Diffusion, Xiaofang Guo, Daniel K. Unruh, Da-Jiang Liu, James W. Evans Feb 2012

Tricriticality In Generalized Schloegl Models For Autocatalysis: Lattice-Gas Realization With Particle Diffusion, Xiaofang Guo, Daniel K. Unruh, Da-Jiang Liu, James W. Evans

Physics and Astronomy Publications

We analyze lattice–gas reaction–diffusion models which include spontaneous annihilation, autocatalytic creation, and diffusion of particles, and which incorporate the particle creation mechanisms of both Schloegl’s first and second models. For fixed particle diffusion or hop rate, adjusting the relative strength of these creation mechanisms induces a crossover between continuous and discontinuous transitions to a “poisoned” vacuum state. Kinetic Monte Carlo simulations are performed to map out the corresponding tricritical line as a function of hop rate. An analysis is also provided of the tricritical “epidemic exponent” for the case of no hopping. The phase diagram is also ...


Gluon Saturation Effects On The Color Singlet J/Psi Production In High Energy Da And Aa Collisions, F. Dominguez, D. E. Kharzeev, E. M. Levin, A. H. Mueller, Kirill Tuchin Jan 2012

Gluon Saturation Effects On The Color Singlet J/Psi Production In High Energy Da And Aa Collisions, F. Dominguez, D. E. Kharzeev, E. M. Levin, A. H. Mueller, Kirill Tuchin

Physics and Astronomy Publications

We derive the formulae for the cross section of J/Psi production in high energy pA and AA collisions taking into account the gluon saturation/color glass condensate effects. We then perform the numerical calculations of the corresponding nuclear modification factors and find a good agreement between our calculations and the experimental data on . J/Psi production in pA collisions. We also observe that cold nuclear modification effects alone cannot describe the data on . J/Psi production in AA collisions. Additional final state suppression (at RHIC) and enhancement (at LHC) mechanisms are required to explain the experimental observations.


Properties Of Inclusive Hadron Production In Deep Inelastic Scattering On Heavy Nuclei At Low X, Kirill Tuchin, Dajiing Wu Jan 2012

Properties Of Inclusive Hadron Production In Deep Inelastic Scattering On Heavy Nuclei At Low X, Kirill Tuchin, Dajiing Wu

Physics and Astronomy Publications

We present a comprehensive study of inclusive hadron production in deep inelastic scattering (DIS) at low x. Properties of the hadron spectrum are different in different kinematic regions formed by three relevant momentum scales: photon virtuality Q2, hadron transverse momentum k T and the saturation momentum Q s(x). We investigate each kinematic region and derive the corresponding asymptotic formulas for the cross section at the leading logarithmic order. We also analyze the next-to-leading-order corrections to the Balitskii-Fadin-Kuraev-Lipatov kernel that are responsible for the momentum conservation. In particular, we establish the asymptotic behavior of the forward elastic dipole-nucleus scattering amplitude ...