Heavy quarkonium correlators at finite temperature: QCD sum rule approach

We investigate the properties of heavy quarkonia at finite temperature in detail using QCD sum rules. Extending previous analyses, we take into account a temperature dependent effective continuum threshold and derive constraints on the mass, the width, and the varying effective continuum threshold. We find that at least one of these quantities of a charmonium changes abruptly in the vicinity of the phase transition. We also calculate the ratio of the imaginary time correlator to its reconstructed one, $G/G_{\text{rec}}$, by constructing a model spectral function and compare it to the corresponding lattice QCD results. We demonstrate that the almost constant unity of $G/G_{\text{rec}}$ can be obtained from the destructive interplay of the changes in each part of the spectral modification which are extracted from QCD sum rules.Comment: Revised version to appear in PRD. 31 pages, 31 figures. Title is change

Does the 2D Hubbard Model Really Show d-Wave Superconductivity?

Some issues concerning the question if the two-dimensional Hubbard model really show d-wave superconductivity are briefly discussed.Comment: Revtex, no figure

Nonconical theory of flow past slender wing bodies with leading-edge separation

Nonconical theory of flow past slender wing bodies with leading edge separatio

Bahasa dan Ideologi: Mengungkap Ideologi dan Kekuasaan Simbolik di Balik Penggunaan Bahasa (Kajian Teks Media melalui Analisis Wacana Kritis)

Tulisan ini didasari sebuah anggapan bahwa bahasa tidak berada di ruang hampa sosial.Maka, bahasa pada dasarnya bukan hanya untaian kata yang hanya bersifat linguistik, tetapi bersifat sosial. Karenanya, bahasa dipahami sebagai tindakan sosial.Implikasinya, bahasa bukan hanya bermatra linguistik, tetapi juga bermatra sosial. Van Dijk menjadi salah satu model yang dapat digunakan sebagai alat untuk menganalisis wacana secara kritis. Penelitian analisis wacana kritis model van Dijk mempertimbangkan teks, konteks, kognisi sosial, dan analisis/konteks sosial. Untuk mengungkap hal itu, langkah yang dapat dilakukan adalah: mengungkap struktur makro (tematik), suprstruktur (skematik), dan struktur mikro yang terdiri atas semantik, sintaksis, stilitistik, dan retorika. Untuk mengungkap hal itu, di sini digunakan metode simak dan catat dengan menjadikan Suara Merdeka dan Kompassebagai sumber datanya. Hasilnya pertama,SM cenderung berideologi kasar, provokatif, dan konotatif/figuratif. Hal itu, tampak pada pilihan kata/kalimat kata yang cenderung kasar, seperti mengancam,menyerang, memanggil paksa, menyeret, menembak.Sementara, harian K cenderung berideologi idealisme pers yang objektif, netral, dan berimbang. Kedua, dari dimensi kekuasaan (simbolik), harian SM cenderung menjadi “oposisi” dan “oposan”sebagai pihak yang di-dominan-kan, sedang pihak pemerintah sebagai pihak yang “dimarginalkan”. Sementara, harian K menempatkan pihak yang dominan/marginal lebih didasarkan pada kondisi objektif di lapangan yang berbasis data dan keterangan yang dari narasumber yang cenderung netral, seperti pengamat, warga, dan akademisi; tidak didasarkan pada keterangan yang cenderung subjektif, seperti dari para politisi.Ketiga, dari sisi analisis sosial dan kognisi sosial; SM lebih tampak sebagai cerminan tagline-nya yaitu lokal (yaitu “perekat komunitas Jawa Tengah”), sedangkan harian K lebih “mengabdi” pada rakyat seperti tampak pada tagline-nya “Amanat Hati Nurani Rakyat” sehingga “suara” rakyatlah yang diungkapnya tanpa mengarah menjadi partisan

Renormalization of the Sigma-Omega model within the framework of U(1) gauge symmetry

It is shown that the Sigma-Omega model which is widely used in the study of nuclear relativistic many-body problem can exactly be treated as an Abelian massive gauge field theory. The quantization of this theory can perfectly be performed by means of the general methods described in the quantum gauge field theory. Especially, the local U(1) gauge symmetry of the theory leads to a series of Ward-Takahashi identities satisfied by Green's functions and proper vertices. These identities form an uniquely correct basis for the renormalization of the theory. The renormalization is carried out in the mass-dependent momentum space subtraction scheme and by the renormalization group approach. With the aid of the renormalization boundary conditions, the solutions to the renormalization group equations are given in definite expressions without any ambiguity and renormalized S-matrix elememts are exactly formulated in forms as given in a series of tree diagrams provided that the physical parameters are replaced by the running ones. As an illustration of the renormalization procedure, the one-loop renormalization is concretely carried out and the results are given in rigorous forms which are suitable in the whole energy region. The effect of the one-loop renormalization is examined by the two-nucleon elastic scattering.Comment: 32 pages, 17 figure

Symmetry restrictions in chirality dependence of physical properties of single wall nanotubes

We investigate the chirality dependence of physical properties of nanotubes which are wrapped by the planar hexagonal lattice including graphite and boron nitride sheet, and reveal its symmetry origin. The observables under consideration are of scalar, vector and tensor types. These exact chirality dependence obtained are useful to verify the experimental and numerical results and propose accurate empirical formulas. Some important features of physical quantities can also be extracted by only considering the symmetry restrictions without complicated calculations.Comment: 5 pages, 1 figure

Thermodynamics of spin-1/2 tetrameric Heisenberg antiferromagnetic chain

The thermodynamic properties of a spin S=1/2 tetrameric Heisenberg antiferromagnetic chain with alternating interactions AF1-AF2-AF1-F (AF and F denote the antiferromagnetic and ferromagnetic couplings, respectively) are studied by means of the transfer-matrix renormalization group method and Jordan-Wigner transformation. It is found that in the absence of magnetic field, the thermodynamic behaviors are closely related to the gapped low-lying excitations, and a novel structure with three peaks in the temperature dependence of specific heat is unveiled. In a magnetic field, a phase diagram in the temperature-field plane for the couplings satisfying JAF1=JAF2=JF is obtained, in which various phases are identified. The temperature dependence of thermodynamic quantities including the magnetization, susceptibility and specific heat are studied to characterize the corresponding phases. It is disclosed that the magnetization has a crossover behavior at low temperature in the Luttinger liquid phase, which is shown falling into the same class as that in the S=1 Haldane chain. In the plateau regime, the thermodynamic behaviors alter at a certain field, which results from the crossing of two excitation spectra. By means of the fermion mapping, it is uncovered that the system has four spectra from fermion and hole excitations that are responsible for the observed thermodynamic behaviors.Comment: 10 pages, 10 figures, accepted by Phys. Rev.

First- and Second-Order Phase Transitions, Fulde-Ferrel Inhomogeneous State and Quantum Criticality in Ferromagnet/Superconductor Double Tunnel Junctions

First- and second-order phase transitions, Fulde-Ferrel (FF) inhomogeneous superconducting (SC) state and quantum criticality in ferromagnet/superconductor/ferromagnet double tunnel junctions are investigated. For the antiparallel alignment of magnetizations, it is shown that a first-order phase transition from the homogeneous BCS state to the inhomogeneous FF state occurs at a certain bias voltage $V^{\ast}$; while the transitions from the BCS state and the FF state to the normal state at $V_{c}$ are of the second-order. A phase diagram for the central superconductor is presented. In addition, a quantum critical point (QCP), $$, is identified. It is uncovered that near the QCP, the SC gap, the chemical potential shift induced by the spin accumulation, and the difference of free energies between the SC and normal states vanish as $$ with the quantum critical exponents $z\nu =1/2$, 1 and 2, respectively. The tunnel conductance and magnetoresistance are also discussed.Comment: 5 pages, 4 figures, Phys. Rev. B 71, 144514 (2005