cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Positive trace polynomials and the universal Procesi-Schacher conjecture
Creators: name: Klep, Igor
name: Špenko, Špela
name: Volčič, Jurij
Publisher: name: arXiv
Year: 2017
Subjects: subject: Rings and Algebras (math.RA)
subject: FOS: Mathematics

description: Positivstellensatz is a fundamental result in real algebraic geometry providing algebraic certificates for positivity of polynomials on semialgebraic sets. In this article Positivstellensätze for trace polynomials positive on semialgebraic sets of $n\times n$ matrices are provided. A Krivine-Stengle-type Positivstellensatz is proved characterizing trace polynomials nonnegative on a general semialgebraic set $K$ using weighted sums of hermitian squares with denominators. The weights in these certificates are obtained from generators of $K$ and traces of hermitian squares. For compact semialgebraic sets $K$ Schmüdgen- and Putinar-type Positivstellensätze are obtained: every trace polynomial positive on $K$ has a sum of hermitian squares decomposition with weights and without denominators. The methods employed are inspired by invariant theory, classical real algebraic geometry and functional analysis. Procesi and Schacher in 1976 developed a theory of orderings and positivity on central simple algebras with involution and posed a Hilbert's 17th problem for a universal central simple algebra of degree $n$: is every totally positive element a sum of hermitian squares? They gave an affirmative answer for $n=2$. In this paper a negative answer for $n=3$ is presented. Consequently, including traces of hermitian squares as weights in the Positivstellensätze is indispensable.
Nonlinear resonant oscillation of gravitational potential induced by ultralight axion in $f(R)$ gravity
Creators: name: Aoki, Arata
name: Soda, Jiro
Publisher: name: arXiv
Year: 2017
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We study the ultralight axion dark matter with mass around $10^{-22}$ eV in $f(R)$ gravity which might resolve the dark energy problem. In particular, we focus on the fact that the pressure of the axion field oscillating in time produces oscillations of gravitational potentials. We show that the oscillation of the gravitational potential is sensitive to the model of gravity. Remarkably, we find that the detectability of the oscillation through the gravitational wave detectors can be significantly enhanced due to the nonlinear resonance between the ultralight axion and the scalaron.
description: 9 pages, 4 figures, published version
$K^+$-nucleus elastic scattering revisited from perspective of partial restoration of chiral symmetry
Creators: name: Aoki, Kenji
name: Jido, Daisuke
Publisher: name: arXiv
Year: 2017
Subjects: subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: The $K^{+}$ meson properties in the nuclear medium are investigated by considering the wavefunction renormalization as a first step to reveal the in-medium properties of the $K^{+}$ meson in the context of partial restoration of chiral symmetry. The $K^{+}N$ elastic scattering amplitude is constructed using chiral perturbation theory up to the next-to-leading order. Using the constructed amplitude, we calculate the wavefunction renormalization in the Thomas-Fermi approximation. We obtained a good description of the $K^{+}N$ elastic scattering amplitude. The obtained wavefunction renormalization factor suggests the 2 to 6% enhancement of the $K^{+}N$ interaction at the saturation density. We conclude that the wavefunction renormalization could be one of the important medium effects for the $K^{+}$ meson.
Rigid Cohomology of Drinfeld's Upper Half Space over a Finite Field
Creators: name: Kuschkowitz, Mark
Publisher: name: arXiv
Year: 2017
Subjects: subject: Number Theory (math.NT)
subject: FOS: Mathematics

description: In this paper the rigid cohomology of Drinfeld's upper half space over a finite field is computed in two ways. The first method proceeds by computation of the rigid cohomology of the complement of Drinfeld's upper half space in the ambient projective space and then use of the associated long exact sequence for rigid cohomology with proper supports. The second method proceeds by direct computation of rigid cohomology as a direct limit of de Rham cohomologies of a family of strict open neighborhoods of the tube of Drinfeld's upper half space in the ambient rigid-analytic projective space. The resulting cohomology formula has been known since 2007, when Grosse-Kloenne proved that it is the same as the one obtained from l-adic cohomology.
description: 30 pages, v2, final version as appeared in Math. Z (2017)
Multiple Dirac Cones and Topological Magnetism in Honeycomb-Monolayer Transition Metal Trichalcogenides
Creators: name: Sugita, Yusuke
name: Miyake, Takashi
name: Motome, Yukitoshi
Publisher: name: arXiv
Year: 2017
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: The discovery of monolayer graphene has initiated two fertile fields in modern condensed matter physics, Dirac semimetals and atomically-thin layered materials. When these trends meet again in transition metal compounds, which possess spin and orbital degrees of freedom and strong electron correlations, more exotic phenomena are expected to emerge in the cross section of topological states of matter and Mott physics. Here, we show by using ab initio calculations that a monolayer form of transition metal trichalcogenides (TMTs), which has a honeycomb network of transition metal cations, may exhibit multiple Dirac cones with tunable gaps in the electronic structure. Furthermore, we elucidate that electron correlations and carrier doping turn the multiple-Dirac semimetal into a topological ferromagnet with high Chern number. Our findings raise the honeycomb-monolayer TMTs to a new paradigm to explore correlated Dirac electrons and topologically-nontrivial magnetism. In turn, the unique wide-ranging properties of the materials will deliver new building blocks for atomically thin heterostructures.
description: 8 pages, 8 figures, 4 tables
Bogoliubov theory of interacting bosons: new insights from an old problem
Creators: name: Ferrari, Loris
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Gases (cond-mat.quant-gas)
subject: FOS: Physical sciences

description: In a gas of $N$ interacting bosons, the Hamiltonian $H_c$, obtained by dropping all the interaction terms between free bosons with moment $\hbar\mathbf{k}\ne\mathbf{0}$, is diagonalized exactly. The resulting eigenstates $|\:S,\:\mathbf{k},\:η\:\rangle$ depend on two discrete indices $S,\:η=0,\:1,\:\dots$, where $η$ numerates the \emph{quasiphonons} carrying a moment $\hbar\mathbf{k}$, responsible for transport or dissipation processes. $S$, in turn, numerates a ladder of \textquoteleft vacua\textquoteright$\:|\:S,\:\mathbf{k},\:0\:\rangle$, with increasing equispaced energies, formed by boson pairs with opposite moment. Passing from one vacuum to another ($S\rightarrow S\pm1$), results from creation/annihilation of new momentless collective excitations, that we call \emph{vacuons}. Exact quasiphonons originate from one of the vacua by \textquoteleft creating\textquoteright$\:$an asymmetry in the number of opposite moment bosons. The well known Bogoliubov collective excitations (CEs) are shown to coincide with the exact eigenstates $|\:0,\:\mathbf{k},\:η\:\rangle$, i.e. with the quasiphonons created from the lowest-level vacuum ($S=0$). All this is discussed, in view of existing or future experimental observations of the vacuons (PBs), a sort of bosonic Cooper pairs, which are the main factor of novelty beyond Bogoliubov theory.
description: 13 pages, 1 figure
Data-driven polynomial ridge approximation using variable projection
Creators: name: Hokanson, Jeffrey M.
name: Constantine, Paul G.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Numerical Analysis (math.NA)
subject: FOS: Mathematics
subject: 49M15, 62J02, 90C53

description: Inexpensive surrogates are useful for reducing the cost of science and engineering studies involving large-scale, complex computational models with many input parameters. A ridge approximation is one class of surrogate that models a quantity of interest as a nonlinear function of a few linear combinations of the input parameters. When used in parameter studies (e.g., optimization or uncertainty quantification), ridge approximations allow the low dimensional structure to be exploited, reducing the effective dimension. We introduce a new, fast algorithm for constructing a ridge approximation where the nonlinear function is a polynomial. This polynomial ridge approximation is chosen to minimize least squared mismatch between the surrogate and the quantity of interest on a given set of inputs. Naively, this would require optimizing both the polynomial coefficients and the linear combination of weights; the latter of which define a low-dimensional subspace of the input space. However, given a fixed subspace the optimal polynomial can be found by solving a linear least-squares problem, and hence by using variable projection the polynomial can be implicitly found leaving an optimization problem over the subspace alone. We provide an algorithm that finds this polynomial ridge approximation by minimizing over the Grassmann manifold of low-dimensional subspaces using a Gauss-Newton method. We provide details of this optimization algorithm and demonstrate its performance on several numerical examples. Our Gauss-Newton method has superior theoretical guarantees and faster convergence than the alternating approach for polynomial ridge approximation earlier proposed by Constantine, Eftekhari, Hokanson, and Ward [https://doi.org/10.1016/j.cma.2017.07.038] that alternates between (i) optimizing the polynomial coefficients given the subspace and (ii) optimizing the subspace given the coefficients.
Local thermal energy as a structural indicator in glasses
Creators: name: Zylberg, Jacques
name: Lerner, Edan
name: Bar-Sinai, Yohai
name: Bouchbinder, Eran
Publisher: name: arXiv
Year: 2017
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: Materials Science (cond-mat.mtrl-sci)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: Identifying heterogeneous structures in glasses --- such as localized soft spots --- and understanding structure-dynamics relations in these systems remain major scientific challenges. Here we derive an exact expression for the local thermal energy of interacting particles (the mean local potential energy change due to thermal fluctuations) in glassy systems by a systematic low-temperature expansion. We show that the local thermal energy can attain anomalously large values, inversely related to the degree of softness of localized structures in a glass, determined by a coupling between internal stresses --- an intrinsic signature of glassy frustration ---, anharmonicity and low-frequency vibrational modes. These anomalously large values follow a fat-tailed distribution, with a universal exponent related to the recently observed universal $ω^4$ density of states of quasi-localized low-frequency vibrational modes. When the spatial thermal energy field --- a `softness field' --- is considered, this power-law tail manifests itself by highly localized spots which are significantly softer than their surroundings. These soft spots are shown to be susceptible to plastic rearrangements under external driving forces, having predictive powers that surpass those of the normal-modes-based approach. These results offer a general, system/model-independent, physical-observable-based approach to identify structural properties of quiescent glasses and to relate them to glassy dynamics.
description: 8 pages, 4 figures + Supporting Information, shorter title, minor textual changes
Superposition of Macroscopically Distinct States in Adiabatic Quantum Computation
Creators: name: Yuge, Tatsuro
Publisher: name: arXiv
Year: 2017
Subjects: subject: Quantum Physics (quant-ph)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: What are the conditions for adiabatic quantum computation (AQC) to outperform classical computation? Although there exist several quantum adiabatic algorithms achieving the strong quantum speedup, the essential keys to their speedups are still unclear. Here, we investigate the connection between superpositions of macroscopically distinct states and known examples of the speedup in AQC. To formalize this notion we consider an index $p$ that quantifies a superposition of macroscopically distinct states from the asymptotic behaviors of fluctuations of additive observables. We determine this index for five examples of adiabatic algorithms exhibiting various degrees of the speedup. The results suggest that the superposition of macroscopically distinct states is an appropriate indicator of entanglement crucial to the strong quantum speedup in AQC.
description: 15 pages, 1 figure
Can Isolated Single Black Holes Produce X-ray Novae?
Creators: name: Matsumoto, Tatsuya
name: Teraki, Yuto
name: Ioka, Kunihito
Publisher: name: arXiv
Year: 2017
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: Almost all black holes (BHs) and BH candidates in our Galaxy have been discovered as soft X-ray transients, so-called X-ray novae. X-ray novae are usually considered to arise from binary systems. Here we propose that X-ray novae are also caused by isolated single BHs. We calculate the distribution of the accretion rate from interstellar matter to isolated BHs, and find that BHs in molecular clouds satisfy the condition of the hydrogen-ionizaiton disk instability, which results in X-ray novae. The estimated event rate is consistent with the observed one. Possible candidates include IGR J17454-2919, XTE J1908-094, and SAX J1711.6-3808. Near infrared photometric and spectroscopic follow-ups can exclude companion stars for a BH census in our Galaxy.
description: 11 pages, 3 figures, 1 table; accepted by MNRAS
Probing CP-violating Higgs and gauge boson couplings in the Standard Model effective field theory
Creators: name: Ferreira, Felipe
name: Fuks, Benjamin
name: Sanz, Veronica
name: Sengupta, Dipan
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We study the phenomenological consequences of several $CP$-violating structures that could arise in the Standard Model effective field theory framework. Focusing on operators involving electroweak gauge and/or Higgs bosons, we derive constraints originating from Run I LHC data. We then study the capabilities of the present and future LHC runs at higher energies to further probe associated CP-violating phenomena and we demonstrate how differential information can play a key role. We consider both traditional four-lepton probes of CP-violation in the Higgs sector and novel new physics handles based on varied angular and non-angular observables.
description: 17 pages, 13 figures, version accepted by EPJC
Birefringent light propagation on anisotropic cosmological backgrounds
Creators: name: Asenjo, Felipe A.
name: Hojman, Sergio A.
Publisher: name: arXiv
Year: 2017
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: Exact electromagnetic wave solutions to Maxwell equations on anisotropic Bianchi I cosmological spacetime backgrounds are studied. The waves evolving on Bianchi I spacetimes exhibit birefringence (associated to linear polarization) and dispersion. The particular case of a vacuum--dominated anisotropic Universe, which reproduces a Friedmann-Robertson-Walker Universe (for late times) while for earlier times it matches a Kasner Universe, is studied. The electromagnetic waves do not, in general, follow null geodesics. This produces a modification of the cosmological redshift, which is now dependent on light polarization and dispersion and its non-null geodesic behavior. New results presented here may help to tackle some issues related to the "horizon" problem.
description: Accepted in Physical Review D
Spherical metrics with conical singularities on 2-spheres
Creators: name: Dey, Subhadip
Publisher: name: arXiv
Year: 2017
Subjects: subject: Differential Geometry (math.DG)
subject: FOS: Mathematics
subject: 53C20, 57M50

description: Suppose that $θ_1,θ_2,\dots,θ_n$ are positive numbers and $n\ge 3$. Does there exist a sphere with a spherical metric with $n$ conical singularities of angles $2πθ_1,2πθ_2,\dots,2πθ_n$? A sufficient condition was obtained by Gabriele Mondello and Dmitri Panov (arXiv:1505.01994). We show that it is also necessary when we assume that $θ_1,θ_2,\dots,θ_n \not\in \mathbb{N}$.
description: In this updated version, the proof of the main result has been changed, and is now more geometric in nature. 9 pages, 1 figure
Mesic nuclei with a heavy antiquark
Creators: name: Yamaguchi, Yasuhiro
name: Yasui, Shigehiro
Publisher: name: arXiv
Year: 2016
Subjects: subject: Nuclear Theory (nucl-th)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: The binding system of a hadron and a nucleus is a topic of great interest for investigating the hadron properties. In the heavy-flavor region, the attraction between a $P(=\bar{D},B)$ meson and a nucleon $N$ can appear, where the $PN-P^\ast N$ mixing plays an important role in relation to the heavy-quark spin symmetry. The attraction can produce exotic heavy mesic nuclei that are stable against the strong decay. We study an exotic system where the $\bar{D}$ ($B$) meson and nucleus are bound. The meson-nucleus interaction is given by a folding potential with single-channel $PN$ interaction and the nucleon number distribution function. By solving the Schrödinger equations of the heavy meson and the nucleus, we obtain several bound and resonant states for nucleon number $A=16,\dots,208$. The results indicate the possible existence of exotic mesic nuclei with a heavy antiquark.
description: 18 pages, 9 figures and 3 tables, published version
Perturbative density functional methods for cholesteric liquid crystals
Creators: name: Tortora, Maxime M. C.
name: Doye, Jonathan P. K.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: FOS: Physical sciences

description: We introduce a comprehensive numerical framework to generically infer the emergent macroscopic properties of uniaxial nematic and cholesteric phases from that of their microscopic constituent mesogens. This approach, based on the full numerical resolution of the Poniewierski-Stecki equations in the weak chirality limit, may expediently handle a wide range of particle models through the use of Monte-Carlo sampling for all virial-type integrals. Its predictions in terms of equilibrium cholesteric structures are found to be in excellent agreement with previous full-functional descriptions, thereby demonstrating the quantitative validity of the perturbative treatment of chirality for pitch lengths as short as a few dozen particle diameters. Furthermore, the use of the full angle-dependent virial coefficients in the Onsager-Parsons-Lee formalism increases its numerical efficiency by several orders of magnitude over that of these previous methods. The comparison of our results with numerical simulations however reveals some shortcomings of the Parsons-Lee approximation for systems of strongly non-convex particles, notwithstanding the accurate inclusion of their full effective molecular volume. Further potential limitations of our theory in terms of phase symmetry assumptions are also examined, and prospective directions for future improvements discussed.
Critical two-point function for long-range $O(n)$ models below the upper critical dimension
Creators: name: Lohmann, Martin
name: Slade, Gordon
name: Wallace, Benjamin C.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Mathematical Physics (math-ph)
subject: Probability (math.PR)
subject: FOS: Physical sciences
subject: FOS: Mathematics
subject: 82B28, 82B27, 82B20, 60K35

description: We consider the $n$-component $|φ|^4$ lattice spin model ($n \ge 1$) and the weakly self-avoiding walk ($n=0$) on $\mathbb{Z}^d$, in dimensions $d=1,2,3$. We study long-range models based on the fractional Laplacian, with spin-spin interactions or walk step probabilities decaying with distance $r$ as $r^{-(d+α)}$ with $α\in (0,2)$. The upper critical dimension is $d_c=2α$. For $ε>0$, and $α= \frac 12 (d+ε)$, the dimension $d=d_c-ε$ is below the upper critical dimension. For small $ε$, weak coupling, and all integers $n \ge 0$, we prove that the two-point function at the critical point decays with distance as $r^{-(d-α)}$. This "sticking" of the critical exponent at its mean-field value was first predicted in the physics literature in 1972. Our proof is based on a rigorous renormalisation group method. The treatment of observables differs from that used in recent work on the nearest-neighbour 4-dimensional case, via our use of a cluster expansion.
description: 32 pages
Adding dynamical generators in quantum master equations
Creators: name: Kolodynski, Jan
name: Brask, Jonatan Bohr
name: Perarnau-Llobet, Marti
name: Bylicka, Bogna
Publisher: name: arXiv
Year: 2017
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: The quantum master equation is a widespread approach to describing open quantum system dynamics. In this approach, the effect of the environment on the system evolution is entirely captured by the dynamical generator, providing a compact and versatile description. However, care needs to be taken when several noise processes act simultaneously or the Hamiltonian evolution of the system is modified. Here, we show that generators can be added at the master equation level without compromising physicality only under restrictive conditions. Moreover, even when adding generators results in legitimate dynamics, this does not generally correspond to the true evolution of the system. We establish a general condition under which direct addition of dynamical generators is justified, showing that it is ensured under weak coupling and for settings where the free system Hamiltonian and all system-environment interactions commute. In all other cases, we demonstrate by counterexamples that the exact evolution derived microscopically cannot be guaranteed to coincide with the dynamics naively obtained by adding the generators.
description: Significantly restructured and rewritten to improve presentation and clarity. 27 pages (12 main + 15 appendices), 5 figures
Raman anomalies as signatures of pressure induced electronic topological and structural transitions in black phosphorus: Experiments and Theory
Creators: name: Gupta, Satyendra Nath
name: Singh, Anjali
name: Pal, Koushik
name: Chakraborti, Biswanath
name: Muthu, D. V. S.
name: Waghmare, U V
name: Sood, A. K.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We report high pressure Raman experiments of Black phosphorus up to 24 GPa. The line widths of first order Raman modes A$^1_g$, B$_{2g}$ and A$^2_g$ of the orthorhombic phase show a minimum at 1.1 GPa. Our first-principles density functional analysis reveals that this is associated with the anomalies in electron-phonon coupling at the semiconductor to topological insulator transition through inversion of valence and conduction bands marking a change from trivial to nontrivial electronic topology. The frequencies of B$_{2g}$ and A$^2_g$ modes become anomalous in the rhombohedral phase at 7.4 GPa, and new modes appearing in the rhombohedral phase show anomalous softening with pressure. This is shown to originate from unusual structural evolution of black phosphorous with pressure, based on first-principles theoretical analysis.
description: 13pages, 12figures
Synchronization dynamics of two nanomechanical membranes within a Fabry-Perot cavity
Creators: name: Bemani, F.
name: Motazedifard, Ali
name: Roknizadeh, R.
name: Naderi, M. H.
name: Vitali, D.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Spontaneous synchronization is a significant collective behavior of weakly coupled systems. Due to their inherent nonlinear nature, optomechanical systems can exhibit self-sustained oscillations which can be exploited for synchronizing different mechanical resonators. In this paper, we explore the synchronization dynamics of two membranes coupled to a common optical field within a cavity, and pumped with a strong blue-detuned laser drive. We focus on the system quantum dynamics in the parameter regime corresponding to synchronization of the classical motion of the two membranes. With an appropriate definition of the phase difference operator for the resonators, we study synchronization in the quantum case through the covariance matrix formalism. We find that for sufficiently large driving, quantum synchronization is robust with respect to quantum fluctuations and to thermal noise up to not too large temperatures. Under synchronization, the two membranes are never entangled, while quantum discord behaves similarly to quantum synchronization, that is, it is larger when the variance of the phase difference is smaller.
Invariant-based inverse engineering of crane control parameters
Creators: name: González-Resines, S.
name: Guéry-Odelin, D.
name: Tobalina, A.
name: Lizuain, I.
name: Torrontegui, E.
name: Muga, J. G.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Quantum Physics (quant-ph)
subject: Applied Physics (physics.app-ph)
subject: FOS: Physical sciences

description: By applying invariant-based inverse engineering in the small-oscillations regime, we design the time dependence of the control parameters of an overhead crane (trolley displacement and rope length), to transport a load between two positions at different heights with minimal final energy excitation for a microcanonical ensemble of initial conditions. The analogies between ion transport in multisegmented traps or neutral atom transport in moving optical lattices and load manipulation by cranes opens a route for a useful transfer of techniques among very different fields.
description: 9 pages, 5 figures
A lower bound for the BCS functional with boundary conditions at infinity
Creators: name: Deuchert, Andreas
Publisher: name: arXiv
Year: 2017
Subjects: subject: Mathematical Physics (math-ph)
subject: Quantum Gases (cond-mat.quant-gas)
subject: Superconductivity (cond-mat.supr-con)
subject: Analysis of PDEs (math.AP)
subject: FOS: Physical sciences
subject: FOS: Mathematics

description: We consider a many-body system of fermionic atoms interacting via a local pair potential and subject to an external potential within the framework of BCS theory. We measure the free energy of the whole sample with respect to the free energy of a reference state which allows us to define a BCS functional with boundary conditions at infinity. Our main result is a lower bound for this energy functional in terms of expressions that typically appear in Ginzburg-Landau functionals.
description: 32 pages
First measurement of $^{30}$S+$α$ resonant elastic scattering for the $^{30}$S($α$,p) reaction rate
Creators: name: Kahl, D.
name: Yamaguchi, H.
name: Kubono, S.
name: Chen, A. A.
name: Parikh, A.
name: Binh, D. N.
name: Chen, J.
name: Cherubini, S.
name: Duy, N. N.
name: Hashimoto, T.
name: Hayakawa, S.
name: Iwasa, N.
name: Jung, H. S.
name: Kato, S.
name: Kwon, Y. K.
name: Nishimura, S.
name: Ota, S.
name: Setoodehnia, K.
name: Teranishi, T.
name: Tokieda, H.
name: Yamada, T.
name: Yun, C. C.
name: Zhang, L. Y.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Nuclear Experiment (nucl-ex)
subject: FOS: Physical sciences

description: Background: Type I x-ray bursts are the most frequent thermonuclear explosions in the galaxy, resulting from thermonuclear runaway on the surface of an accreting neutron star. The $^{30}$S($α$,p) reaction plays a critical role in burst models, yet insufficient experimental information is available to calculate a reliable, precise rate for this reaction. Purpose: Our measurement was conducted to search for states in $^{34}$Ar and determine their quantum properties. In particular, natural-parity states with large $α$-decay partial widths should dominate the stellar reaction rate. Method: We performed the first measurement of $^{30}$S+$α$ resonant elastic scattering up to a center-of-mass energy of 5.5 MeV using a radioactive ion beam. The experiment utilized a thick gaseous active target system and silicon detector array in inverse kinematics. Results: We obtained an excitation function for $^{30}$S($α$,$α$) near $150^{\circ}$ in the center-of-mass frame. The experimental data were analyzed with an $R$-Matrix calculation, and we observed three new resonant patterns between 11.1 and 12.1 MeV, extracting their properties of resonance energy, widths, spin, and parity. Conclusions: We calculated the resonant thermonuclear reaction rate of $^{30}$S($α$,p) based on all available experimental data of $^{34}$Ar and found an upper limit about one order of magnitude larger than a rate determined using a statistical model. The astrophysical impact of these two rates has been investigated through one-zone postprocessing type I x-ray burst calculations. We find that our new upper limit for the $^{30}$S($α$,p)$^{33}$Cl rate significantly affects the predicted nuclear energy generation rate during the burst.
description: 16 pages, 12 figures
Entanglement entropy and Fisher information metric for closed bosonic strings in homogeneous plane wave background
Creators: name: Dimov, H.
name: Mladenov, S.
name: Rashkov, R. C.
name: Vetsov, T.
Publisher: name: arXiv
Year: 2017
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We derive the extended renormalized entanglement entropy (EREE) and the Fisher information metric in the case of closed bosonic strings in homogeneous plane wave background. Our investigations are conducted within the framework of Thermo Field Dynamics (TFD). The formalism is also illustrated on the example of some particular models in condensed matter physics and the non-equilibrium case for system with dissipations.
description: 24 pages, 10 figures
Robust and Fast Decoding of High-Capacity Color QR Codes for Mobile Applications
Creators: name: Yang, Zhibo
name: Xu, Huanle
name: Deng, Jianyuan
name: Loy, Chen Change
name: Lau, Wing Cheong
Publisher: name: arXiv
Year: 2017
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: FOS: Computer and information sciences

description: The use of color in QR codes brings extra data capacity, but also inflicts tremendous challenges on the decoding process due to chromatic distortion, cross-channel color interference and illumination variation. Particularly, we further discover a new type of chromatic distortion in high-density color QR codes, cross-module color interference, caused by the high density which also makes the geometric distortion correction more challenging. To address these problems, we propose two approaches, namely, LSVM-CMI and QDA-CMI, which jointly model these different types of chromatic distortion. Extended from SVM and QDA, respectively, both LSVM-CMI and QDA-CMI optimize over a particular objective function to learn a color classifier. Furthermore, a robust geometric transformation method and several pipeline refinements are proposed to boost the decoding performance for mobile applications. We put forth and implement a framework for high-capacity color QR codes equipped with our methods, called HiQ. To evaluate the performance of HiQ, we collect a challenging large-scale color QR code dataset, CUHK-CQRC, which consists of 5390 high-density color QR code samples. The comparison with the baseline method [2] on CUHK-CQRC shows that HiQ at least outperforms [2] by 188% in decoding success rate and 60% in bit error rate. Our implementation of HiQ in iOS and Android also demonstrates the effectiveness of our framework in real-world applications.
description: 15 pages, 10 figures, submitted to IEEE Transaction on Image Processing
Simple dual braids, noncrossing partitions and Mikado braids of type $D_n$
Creators: name: Baumeister, Barbara
name: Gobet, Thomas
Publisher: name: arXiv
Year: 2017
Subjects: subject: Group Theory (math.GR)
subject: FOS: Mathematics

description: We show that the simple elements of the dual Garside structure of an Artin group of type $D_n$ are Mikado braids, giving a positive answer to a conjecture of Digne and the second author. To this end, we use an embedding of the Artin group of type $D_n$ in a suitable quotient of an Artin group of type $B_n$ noticed by Allcock, of which we give a simple algebraic proof here. This allows one to give a characterization of the Mikado braids of type $D_n$ in terms of those of type $B_n$ and also to describe them topologically. Using this topological representation and Athanasiadis and Reiner's model for noncrossing partitions of type $D_n$ which can be used to represent the simple elements, we deduce the above mentioned conjecture.
description: Minor changes
Instability of pulses in gradient reaction-diffusion systems: A symplectic approach
Creators: name: Beck, Margaret
name: Cox, Graham
name: Jones, Christopher
name: Latushkin, Yuri
name: McQuighan, Kelly
name: Sukhtayev, Alim
Publisher: name: arXiv
Year: 2017
Subjects: subject: Dynamical Systems (math.DS)
subject: Mathematical Physics (math-ph)
subject: Classical Analysis and ODEs (math.CA)
subject: FOS: Mathematics
subject: FOS: Physical sciences

description: In a scalar reaction-diffusion equation, it is known that the stability of a steady state can be determined from the Maslov index, a topological invariant that counts the state's critical points. In particular, this implies that pulse solutions are unstable. We extend this picture to pulses in reaction-diffusion systems with gradient nonlinearity. In particular, we associate a Maslov index to any asymptotically constant state, generalizing existing definitions of the Maslov index for homoclinic orbits. It is shown that this index equals the number of unstable eigenvalues for the linearized evolution equation. Finally, we use a symmetry argument to show that any pulse solution must have nonzero Maslov index, and hence be unstable.
description: 19 pages, 1 figure. To appear in Philos. Trans. Roy. Soc. A
The properties of active galaxies at the extreme of eigenvector 1
Creators: name: Sniegowska, M.
name: Czerny, B.
name: You, B.
name: Panda, S.
name: Wang, J. -M.
name: Hryniewicz, K.
name: Wildy, C.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: Eigenvector 1 (EV1) is the formal parameter which allows the introduction of some order in the properties of the unobscured type 1 active galaxies. We aim to understand the nature of this parameter by analyzing the most extreme examples of quasars with the highest possible values of the corresponding eigenvalues $R_{Fe}$. We selected the appropriate sources from the Sloan Digital Sky Survey (SDSS) and performed detailed modeling, including various templates for the Fe II pseudo-continuum and the starlight contribution to the spectrum. Out of 27 sources with $R_{Fe}$ larger than 1.3 and with the measurement errors smaller than 20\% selected from the SDSS quasar catalog, only six sources were confirmed to have a high value of $R_{Fe}$, defined as being above 1.3. All other sources have $an R_{Fe}$ of approximately 1. Three of the high $R_{Fe}$ objects have a very narrow H$β$ line, below 2100 km s$^{-1}$ but three sources have broad lines, above 4500 km s$^{-1}$, that do not seem to form a uniform group, differing considerably in black hole mass and Eddington ratio; they simply have a very similar EW([OIII]5007) line. Therefore, the interpretation of the EV1 remains an open issue.
description: Astronomy and Astrophysics (in press)
title: Development of a family business entitled "Pistachio tour"
title: Ανάπτυξη οικογενειακής επιχείρησης με τίτλο "Pistachio tour"
titleType: AlternativeTitle
Creators: name: Τουρλάκη, Χριστίνα
Publisher: name: Πανεπιστήμιο Δυτικής Αττικής
Year: 2023
Subjects: Οικογενειακή επιχείρηση
Κελυφωτό φιστίκι Φθιώτιδας ΠΟΠ
Ιστοσελίδα
E-shop
Λογότυπο
Προωθητικές ενέργειες

description: In this theoretical work, the development stages of the design of the family business “Pistachio tour” are recorded, which manufactures products with the PDO Fthiotida shelled pistachio as its main ingredient. More specifically, reference is made to the peanut itself and its benefits. This is followed by a study and research on similar businesses that are on the market. While the course and evolution of the design of the logo, the corporate identity, the products, the promotional actions and the cen- tral e-shop website of the company is being developed.
Collective diffusion and quantum chaos in holography
Creators: name: Wu, Shao-Feng
name: Wang, Bin
name: Ge, Xian-Hui
name: Tian, Yu
Publisher: name: arXiv
Year: 2017
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We define a particular combination of charge and heat currents that is decoupled with the heat current. This `heat-decoupled' (HD) current can be transported by diffusion at long distances, when some thermo-electric conductivities and susceptibilities satisfy a simple condition. Using the diffusion condition together with the Kelvin formula, we show that the HD diffusivity can be same as the charge diffusivity and also the heat diffusivity. We illustrate that such mechanism is implemented in a strongly coupled field theory, which is dual to a Lifshitz gravity with the dynamical critical index z=2. In particular, it is exhibited that both charge and heat diffusivities build the relationship to the quantum chaos. Moreover, we study the HD diffusivity without imposing the diffusion condition. In some homogeneous holographic lattices, it is found that the diffusivity/chaos relation holds independently of any parameters, including the strength of momentum relaxation, chemical potential, or temperature. We also show a counter example of the relation and discuss its limited universality.
description: v4: 26 pages, 1 figure, major revision
Degrees of Irreducible Morphisms over Perfect Fields
Creators: name: Chaio, Claudia
name: Meur, Patrick Le
name: Trepode, Sonia
Publisher: name: arXiv
Year: 2017
Subjects: subject: Representation Theory (math.RT)
subject: FOS: Mathematics
subject: 16G10, 16G60, 16G70

description: The module category of any artin algebra is filtered by the powers of its radical, thus defining an associated graded category. As an extension of the degree of irreducible morphisms, this text introduces the degree of morphisms in the module category in terms of the induced natural transformations between representable functors on this graded category. When the ground ring is a perfect field, and the given morphism behaves nicely with respect to covering theory (as do irreducible morphisms with indecomposable domain or indecomposable codomain), it is shown that the degree of the morphism is finite if and only if its associated natural transformation has a representable kernel. As a corollary, generalisations of known results on the degrees of irreducible morphisms over perfect fields are given. Finally, this study is applied to the composition of paths of irreducible morphisms in relationship to the powers of the radical.
description: Final version to appear in Algebras and Representation Theory. Due to changes in arXiv:1412.0188, the theorem C and the proposition 5.02 (4.0.2 in v.1) are slightly reformulated and the morphisms called <> in v.1 are now called <>. Sections renumbered to stick to the published version. Minor changes and corrections
Πληροφόρηση (intelligence) και ευρωπαϊκή ολοκλήρωση : ισχύον πλαίσιο, διαχρονικά εμπόδια, κίνητρα και αναγκαιότητα σύστασης Ευρωπαϊκής Υπηρεσίας Πληροφοριών
Creators: name: Καφούκα, Άννα-Νικολέττα
Publisher: name: Πανεπιστήμιο Πειραιώς
Year: 2023
Subjects: subject: Ευρωπαϊκή Ένωση
subject: Κοινή Εξωτερική Πολιτική και Πολιτική Ασφαλείας (ΚΕΠΠΑ)
subject: Πληροφόρηση
subject: Ευρωπαϊκή Υπηρεσία Πληροφοριών
subject: Θεσμικά Όργανα
subject: Αναθεώρηση συνθηκών
subject: European Union
subject: Common Foreign and Security Policy (CFSP)
subject: Intelligence
subject: European Intelligence Service
subject: Security institutions
subject: Treaties revision

description: Η σύγχρονη πραγματικότητα υπαγορεύει ως επιτακτική τη σύσταση μιας αυτοτελούς και ανεξάρτητης Ευρωπαϊκής Υπηρεσίας Πληροφοριών, κάτι περισσότερο, δηλαδή, από ένα ετερογενές ευρωπαϊκό δίκτυο πληροφόρησης. Οι νέες απειλές, εσωτερικές και εξωτερικές, έχουν αναδιαμορφώσει το διεθνές περιβάλλον ασφαλείας και η σύσταση μιας τέτοιας υπηρεσίας σε ευρωπαϊκό πλαίσιο θα μπορούσε να συμβάλει αποτελεσματικά τόσο στην πρόληψη όσο και στην αντιμετώπισή τους, να ενισχύσει δηλαδή την ανθεκτικότητα (resilience) της Ευρωπαϊκής Ένωσης (εφεξής ΕΕ). Αν και έχουν γίνει βήματα σε ευρωπαϊκό επίπεδο, στο πλαίσιο των πολιτικών ασφαλείας της ΕΕ, οι υπάρχοντες Οργανισμοί στο πεδίο της πληροφόρησης (intelligence), παρά την αδιαμφισβήτητα σημαντική συνδρομή τους, παρουσιάζουν ατέλειες και ελλείψεις σε πολλούς τομείς, που τους καθιστούν δυσλειτουργικούς και ίσως ανήμπορους να σταθούν απέναντι στις σύγχρονες προκλήσεις. Παρουσιάζοντας τα κυριότερα ζητήματα ασφαλείας στο σύγχρονο διεθνές περιβάλλον, εξετάζοντας την υπάρχουσα ευρωπαϊκή αρχιτεκτονική στον τομέα της ασφάλειας και της πληροφόρησης, αναλύοντας τα εμπόδια, που διαχρονικά καθυστερούν και δυσχεραίνουν την επίτευξη ενός τέτοιου εγχειρήματος, και τα κίνητρα για την υλοποίηση του επόμενου σταδίου, η παρούσα εργασία επιχειρηματολογεί υπέρ της αναγκαιότητας αναδιαμόρφωσης του χαρακτήρα της ευρωπαϊκής συνεργασίας στον τομέα της πληροφόρησης σε ένα νομικά και πολιτικά ανεξάρτητο κεντρικό φορέα, επιφορτισμένο τόσο με τη συλλογή και την ανάλυση όσο και με τη διαχείριση των πληροφοριών. Το εγχείρημα αυτό αποτελεί πρόκληση όχι μόνο για τα κράτη-μέλη, τα οποία θα επηρεαστούν άμεσα, αλλά και για την ίδια την Ένωση ως οντότητα που βαδίζει προς μια πιο ολοκληρωμένη μορφή. Στο σημείο αυτό, κρίνεται σκόπιμο να αναφερθεί ότι, αν και αποτελεί εύλογο ερώτημα και σημαντική πτυχή του κεντρικού ζητήματος ενδιαφέροντος, η παρούσα εργασία δεν κινείται γύρω από επιχειρησιακά και τεχνικά ζητήματα υλοποίησης ενός τέτοιου εγχειρήματος, αλλά κύριος άξονας μελέτης είναι η τρέχουσα κατάσταση και οι προτεινόμενες αλλαγές σε θεσμικό επίπεδο.
Energy-dependent variability of the bare Seyfert 1 galaxy Ark 120
Creators: name: Mallick, Labani
name: Dewangan, Gulab C.
name: McHardy, I. M.
name: Pahari, Mayukh
Publisher: name: arXiv
Year: 2017
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: We present results from a detailed spectral-timing analysis of a long ~486 ks XMM-Newton observation of the bare Seyfert 1 galaxy Ark 120 which showed alternating diminution and increment in the 0.3-10 keV X-ray flux over four consecutive orbits in 2014. We study the energy-dependent variability of Ark 120 through broad-band X-ray spectroscopy, fractional root-mean-squared (rms) spectral modelling, hardness-intensity diagram and flux-flux analysis. The X-ray (0.3-10 keV) spectra are well fitted by a thermally Comptonized primary continuum with two (blurred and distant) reflection components and an optically thick, warm Comptonization component for the soft X-ray excess emission below ~2 keV. During the first and third observations, the fractional X-ray variability amplitude decreases with energy while for second and fourth observations, X-ray variability spectra are found to be inverted-crescent and crescent shaped respectively. The rms variability spectra are well modelled by two constant reflection components, a soft excess component with variable luminosity and a variable intrinsic continuum with the normalization and spectral slope being correlated. The spectral softening of the source with both the soft excess and UV luminosities favour Comptonization models where the soft excess and primary X-ray emission are produced through Compton up-scattering of the UV and UV/soft X-ray seed photons in the putative warm and hot coronae, respectively. Our analyses imply that the observed energy-dependent variability of Ark 120 is most likely due to variations in the spectral shape and luminosity of the hot corona and to variations in the luminosity of the warm corona, both of which are driven by variations in the seed photon flux.
description: 17 pages, 19 figures, 6 tables, accepted for publication in MNRAS
Two new Schiff bases of (E)-2,4-di-tert-butyl-6-((4-fluorophenylimino)methyl)phenol (I) and (E)-2,4-di-tert-butyl-6-((3-iodo-4-methylphenylimino)methyl)phenol (II): structural, spectroscopic and quantum chemical calculations
Creators: name: Güzel, Enis
name: Macit, Mustafa
name: Ergüzeloğlu, Ebru
name: Kalecik, Sedanur
name: Keleşoğlu, Zeynep
name: Yavuz, Metin
Publisher: name: Taylor & Francis
Year: 2023
Subjects: subject: Biophysics
subject: Biochemistry
subject: Physical Sciences not elsewhere classified
subject: Chemical Sciences not elsewhere classified
subject: Inorganic Chemistry
subject: FOS: Chemical sciences

description: In this study, two Schiff bases, (E)-2,4-di-tert-butyl-6-((4-fluorophenylimino)methyl)phenol (I) and (E)-2,4-di-tert-butyl-6-((3-iodo-4-methylphenylimino)methyl)phenol (II) are synthesized and characterized by XRD, FT-IR, UV-Vis and NMR techniques. (I) and (II) compounds display enol-imine form by O-H···N intramolecular hydrogen bonds. The title compounds are stabilized by C—H···π interactions. The presence of various inter molecular interactions and 2D-fingerprint regions are well supported by the Hirshfeld surface analysis. Also experimental optical energy band and gap studies are discussed. All chemical theoretical computations are calculated by Density Functional Theory (DFT) at B3LYP level by using 3-21 G basis set. Chemical activity analyses are showed that compounds have large energy gaps, higher values of hardness and lower values of softness support the title molecules are high kinetic stability. Also, chemical activity properties generate foresight about electrophilic and nucleophilic nature. The title compounds characterized by FT-IR, UV-Vis, NMR and XRD techniques.Local and global chemical activity analysis were investigated.Hirshfeld surface analysis revealed the nature of intermolecular contacts, the fingerprint plots and molecular surface contours. The title compounds characterized by FT-IR, UV-Vis, NMR and XRD techniques. Local and global chemical activity analysis were investigated. Hirshfeld surface analysis revealed the nature of intermolecular contacts, the fingerprint plots and molecular surface contours.
Bar evolution: input from simulations
Creators: name: Athanassoula, Lia
Publisher: name: Zenodo
Year: 2023

description: I discuss some of the information on bars provided by numerical simulations of disc galaxies. First I review briefly the older ones neglecting the gas component, and then focus on the effects of gas on the morphology, dynamics and evolution of bars. I compare the results of the simulations with observations and orbital dynamics, and briefly compare bar growth in dynamical and cosmological simulations.