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A física de partículas elementares e o Prêmio Nobel de física 2008
Pleitez, V.;
Revista Brasileira de Ensino de Física , 2008, DOI: 10.1590/S1806-11172008000400001
Abstract: the 2008 nobel prize of physics pay tribute to three theoretical physicist by their work related to some symmetries of nature. we briefly comments the importance of these works and the context in which they were done.
Dynamics and Green’s Functions of Uniaxial Nematic Liquid Crystals  [PDF]
M.Y. Kovalevsky, V.T. Matskevych
Open Access Library PrePrints (OALib PrePrints) , 2014, DOI: 10.4236/oalib.preprints.1200097
Abstract: Dynamics of uniaxial nematic liquid crystals with rod-shaped and disc-shaped molecules in an external field is considered. For the systems under study thermodynamics is constructed and nonlinear dynamic equations accounting for the internal spatial anisotropy and molecules shape are derived. Densities of additive integrals of motion and corresponding flow densities are introduced in terms of thermodynamic potential. Analytical structure of low-frequency asymptotics of two-time Green’s functions is calculated and their characteristics in the region of small wave vectors and frequencies are studied. It is shown that unlike other condensed media with spontaneously broken symmetry low-frequency asymptotics of Green’s functions of considered liquid crystals do not contain divergences of Bogolyubov type.
Violation of Cluster Property in Heisenberg Antiferromagnet  [PDF]
Tomo Munehisa
World Journal of Condensed Matter Physics (WJCMP) , 2018, DOI: 10.4236/wjcmp.2018.84015
Abstract: There are concepts that are accepted in our daily life, but are not trivial in physics. One of them is the cluster property that means there exist no relations between two events which are sufficiently separated. In a paper recently published by the author, it has been pointed out that this cluster property violates in the correlation function of the spin operator for the spin 1/2 XXZ antiferromagnet on the square lattice. In this paper, we investigate the spin 1/2 Heisenberg antiferromagnet on the square lattice, which has SU(2) symmetry. In order to study the cluster property, we need to calculate the ground state accurately. For this purpose, we employ the effective model based on the magnetization of the sub-lattices. Then we can define the quasi-degenerate states to calculate the ground state. Including two kinds of interactions which break SU(2) symmetry into the Hamiltonian, we obtain the ground state quantitatively. We find that two kinds of spin correlation functions due to degenerate states are not zero when the lattice size is large but finite. The magnitude of one of them is the same as the one previously found in the XXZ antiferromagnet, while another one is much larger when the additional interaction is strong. We then conclude that in Heisenberg antiferromagnet correlation functions violate the cluster property and the magnitude of the violation qualitatively differs from the one in the XXZ antiferromagnet.
Directed transport of coupled systems in symmetric periodic potentials
Zheng Zhi-Gang,Liu Feng-Zhi,Gao Jian,
鄭志剛
,劉鳳芝,高建

中國物理 B , 2003,
Abstract: In this paper, we discuss the damped unidirectional motions of a coupled lattice in a periodic potential. Each particle in the lattice is subject to a time-periodic ac force. Our studies reveal that a directed transport process can be observed when the ac forces acting on the coupled lattice have a phase shift (mismatch). This directed motion is a collaboration of the coupling, the substrate potential, and the periodic force, which are all symmetric. The absence of any one of these three factors will not give rise to a directed current. We discuss the complex relations between the directed current and parameters in the system. Results in this paper can be accomplished in experiments. Moreover, our results can be generalized to the studies of directed transport processes in more complicated spatially extended systems.
Light-Front Hamiltonian, Path Integral and BRST Formulations of the Chern-Simons-Higgs Theory in the Broken Symmetry Phase  [PDF]
Usha Kulshreshtha, Daya S. Kulshreshtha, James P. Vary
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.44A007
Abstract:

In the present work we study the Hamiltonian, path integral and BRST formulations of the Chern-Simons-Higgs theory in two-space one-time dimensions, in the so-called broken symmetry phase of the Higgs potential (where the phase φ(xμ) of the complex matter field Φ(xμ) carries the charge degree of freedom of the complex matter field and is akin to the Goldstone boson) on the light-front (i.e., on the hyperplanes defined by the fixed light-cone time). The theory is seen to possess a set of first-class constraints and the local vector gauge symmetry. The theory being gauge-invariant is quantized under appropriate gauge-fixing conditions. The explicit Hamiltonian and path integral quantization is achieved under the above light-cone gauges. The Heisenberg equations of motion of the system are derived for the physical degrees of freedom of the system. Finally the BRST quantization of the system is achieved under appropriate BRST gauge-fixing, where the BRST symmetry is maintained even under the BRST light-cone gauge-fixing.

Diradical character of some fluoranthenes
SVETLANA MARKOVI?,JELENA ?UR?EVI?,SVETLANA JEREMI?,IVAN GUTMAN
Journal of the Serbian Chemical Society , 2010,
Abstract: It is shown that some Kekuléan fluoranthenes are diradicals and that their ground state is a triplet. In the energetically less favorable singlet state, these hydrocarbons also exhibit pronounced diradical character. The diradical character y of the compounds under investigation was estimated using the unrestricted symmetry-broken (yPUHF) and complete active space (yNOON) methods. It was found that the yPUHF values better reproduce the diradical character of the investigated hydrocarbons. It was shown that singly occupied molecular orbital (SOMO) and SOMO-1 of a diradical structure occupy different parts of space with a small shared region, resulting in a spin density distribution over the entire molecule. The spatial diradical distribution in the singlet diradical structures was examined by inspecting the HOMOs and LUMOs for a and b spin electrons. It was shown that the a-HOMO and the b-LUMO (as well as the b-HOMO and the a-LUMO) occupy practically the same part of space. In this way, there are no unpaired electrons in a singlet diradical structure, yet two of them occupy different parts of space, thus allowing the p-electrons to delocalize.
Quasiaverages, symmetry breaking and irreducible Green functions method
A.L.Kuzemsky
Condensed Matter Physics , 2010,
Abstract: The development and applications of the method of quasiaverages to quantum statistical physics and to quantum solid state theory and, in particular, to quantum theory of magnetism, were considered. It was shown that the role of symmetry (and the breaking of symmetries) in combination with the degeneracy of the system was reanalyzed and essentially clarified within the framework of the method of quasiaverages. The problem of finding the ferromagnetic, antiferromagnetic and superconducting "symmetry broken" solutions of the correlated lattice fermion models was discussed within the irreducible Green functions method. A unified scheme for the construction of generalized mean fields (elastic scattering corrections) and self-energy (inelastic scattering) in terms of the equations of motion and Dyson equation was generalized in order to include the "source fields". This approach complements previous studies of microscopic theory of antiferromagnetism and clarifies the concepts of Neel sublattices for localized and itinerant antiferromagnetism and "spin-aligning fields" of correlated lattice fermions.
Theoretical study on magneto-structural correlation of trinuclear copper (II) complex with the hydroxo bridge and bidentate syn-syn carboxylate group
Zhongnan Qi,Jian Wu,Chengbu Liu,Ruoxi Wang,Youmin Sun
Chinese Science Bulletin , 2006, DOI: 10.1007/s11434-006-1421-9
Abstract: The theoretical study on magnetostructural correlation in linear trinuclear Cu (II) complex bridged by hydroxo group and bidentate formato group has been performed using the broken symmetry approach with the framework of density functional theory (DFT-BS). The magnetic coupling constant for the model complex is 70.97 cm 1, comparable with the experimentally measured J value (77 cm 1). The calculated results show that the magnetic coupling interaction firstly slightly increases with the changes of the coordination environment around the terminal Cu atoms from a distorted square pyramid to a trigonal bi-pyramid, and decreases subsequently. In the course of changes, the sign of J value shifts from positive to negative. The magnetic coupling interaction is sensitive to coordination environment of the terminal Cu. The calculated results also reveal that the ferromagnetic coupling arises from the counter-complementarity of the hydroxo and formato bridges. Molecular orbital analysis validates the conclusion.
In Vitro Screening and Selection of Probiotic Lactic Acid Bacteria Isolated from Spontaneously Fermenting Kunu-Zaki  [PDF]
Solakunmi Omotunde Oluwajoba, Felix Akinsola Akinyosoye, Victor Olusegun Oyetayo
Advances in Microbiology (AiM) , 2013, DOI: 10.4236/aim.2013.34044
Abstract:

The present study was conducted to determine the pro-biotic properties in vitro of the lactic acid bacteria isolated from spontaneously fermenting kunu-zaki. Kunu-zaki was processed using composite, non composite, germinated and ungerminated Digitaria exilis (Fonio), Sorghum bicolor (Sorghum) and Pennisetum americanum (Millet) cereals. A total of 150 LAB isolates were obtained from all the fermenting slurries. These 150 LAB isolates were screened for their ability to grow at pH 3.0, resistance against bile salt and ability to inhibit reference test pathogens. Out of these 150 LAB isolates; 21 exhibited good probiotic properties. All the 21 isolates were further identified to specie and subspecies level using standard API50CHL system with all 21 showing good survival (P < 0.05) in a pH 3.0 buffered medium and subsequent resistance to 0.3% bile. The LAB isolates which survived these conditions consisted of 18 Lactobacillus species, 2 Pediococcus species and 1 Lactococcus specie. These LAB species were further examined for antimicrobial activity against the growth of reference pathogens Staphylococcus aureus 25923, Escherichia coli 25922, Pseudomonas aeruginosa 27853 and Enterococcus faecalis 29212. All 21 LAB species exhibited good inhibition of all test reference pathogens except Lactobacillus fructivorans, Lactococcus lactis sp lactis and L. fermentum which however, showed no zone of inhibition against the growth of E. faecalis. Kunu-zaki made from composite un-germinated Sorghum bicolor (Sorghum) and Pennisetum americanum (Millet) cereal grains contained the highest percentage (52%) of LAB species which showed good probiotic criteria in vitro. Non composite ungerminated cereals accounted for 33% of the total probiotic LAB isolates whilst the germinated non composite and composite cereals recorded the lowest percentage (10%) and (5%) of probiotic LAB respectively. The results of this research study showed that the LAB species isolated from wild fermentation of kunu-zaki beverage fulfilled the criteria for in vitro screening of probiotic characteristics. These LAB species possed potential for further use as probiotic in human preparations and suggested the use of kunu-zaki made from ungerminated composite sorghum and millet grains as a natural probiotic drink.

Enrichment Discrimination Behavior in Spontaneously Hypertensive Rats  [PDF]
Ramiz M. Salimov, Georgy I. Kovalev
Journal of Behavioral and Brain Science (JBBS) , 2012, DOI: 10.4236/jbbs.2012.24056
Abstract: Objectives: 1) To reveal, among spontaneously hypertensive rats, subpopulations that diverge in attention to objects enriching an empty cross-maze; 2) To evaluate effect of clinically efficient drug for treatment of attention deficiency atomoxetine on the attention to environmental cues in attentionally-low rats. Method: A novel paradigm that provides measure of attention towards enriching objects independent of general locomotor activity and spatial orientation is employed. The apparatus consists of 4-arm radial maze, two arms of which contain objects (enriched compartments). Animals exploring the objects typically stay longer in enriched parts of maze than in empty arms and have a higher score of enrichment discrimination ratio. Results: Frequency distribution of the enrichment discrimination ratio had clear bimodal shape that differed significantly from normal distribution suggesting the existence of subpopulations of attentionally-low and -high individuals. The attentionally-low phenotype did not show inferiority in spatial orientation as compared with attentionally-high phenotype. The phenotypes did not differ from each other in measures of locomo- tor activity and blood pressure. Atomoxetine (3 mg/kg, orally, once daily for 4 days) enhanced enrichment discrimina- tion in animals of attentionally-low phenotype. Single administration of the drug was ineffective. Conclusion: Popula- tion of spontaneously hypertensive rat includes two phenotypes of attentionally-low and -high individuals. Subchronic atomoxetine ameliorates attention to environmental cues in attentionally-low rats. The enrichment discrimination test could be useful in studies of neurobiology of attention deficit condition and for screening of novel drug candidates.
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