Qweak, N → Δ, and physics beyond the standard model

The data-taking phase of the Qweak experiment ended in May of 2012 at the Thomas Jefferson National Accelerator Facility. Qweak aims to measure the weak charge of the proton, Q _W ^p , via parity-violating elastic electron-proton scattering. The expected value of Q _W ^p is fortuitously suppressed, which leads to an increased sensitivity to physics beyond the Standard Model.     

NΩ and ΔΩ dibaryons in a SU(3) chiral quark model

The binding energy of the six-quark system with strangeness s = −3 is investigated under the chiral SU(3) constituent quark model in the framework of RGM. The calculations of the single NΩ channel with spin S = 2 and the single ΔΩ channel with spin S = 3 are performed. The results show that both systems could be dibaryons and the interaction induced by the chiral field plays a very important role on forming bound states in the systems considered. The phase shifts and scattering lengths in corresponding channels are also given.     

Vibrational Spectroscopic and Theoretical Studies of Urea Derivatives with Biochemical Interest: N,N′-Dimethylurea,N,N,N′,N′-Tetramethylurea,and N,N′-Dimethylpropyleneurea

Abstract

Mid-infrared, far-infrared, and Raman vibrational spectroscopic studies were combined with density functional theory (DFT) calculations and normal coordinate force field analyses for N,N′-dimethylurea (DMU), N,N,N′,N′-tetramethylurea (TMU), and N,N′-dimethylpropyleneurea (DMPU: IUPAC name 1,3-dimethyltetrahydropyrimidin-2(1H)-one). The equilibrium molecular geometry of DMU (all three conformers), TMU, and DMPU and the frequencies, intensities, and depolarization ratios of their fundamental infrared (IR) and Raman vibrational transitions were obtained by DFT calculations. The vibrational spectra were fully analyzed by normal coordinate methods as well. A starting force field for DMPU was obtained by adapting corresponding force constants for DMU and TMU, resulting after refinements in the stretching force constants C=O (7.69, 7.30, 7.68 N·cm^?1), C–N (5.16, 5.55, 5.05 N·cm^?1), and C-Me (5.93, 4.00, 4.22 N·cm^?1) for DMU, TMU, and DMPU, respectively. The dominating conformer of liquid DMU was identified as trans-trans, strong intermolecular hydrogen bonding was verified in solid DMU, and weak dipole–dipole association was found in liquid TMU and in DMPU. Special attention was paid to analyzing the methyl group frequencies, which revealed deviations from local C_3v symmetry. A linear correlation was found between the CH stretching force constants and the inverse of the CH bond lengths (1/r ²). The averaged NH stretching frequencies of gaseous, dissolved, and solid urea and of DMU, with variations for hydrogen bonding of different strength, are linearly correlated to the NH stretching force constants. Characteristic skeletal vibrations were assigned for a broad variety of urea derivatives and also for pyrimidine derivatives, which all contain the N₂C=O entity. The very strong IR bands of C=O stretching (1,676 ± 40 cm^?1) and asymmetric CN₂ stretching (1,478 ± 60 cm^?1), and the very intense Raman feature of symmetric CN₂ stretching or ring breathing (757 ± 80 cm^?1), can be recognized as fingerprint bands also for the pyrimidine derivatives cytosine, thymine, and uracil, which all are nucleobases in DNA and RNA nucleotides.     

CP N−1 models beyond the leading order

We analyse the CP ^N?1 models in two and three dimensions. We discuss the effective potential, Greens functions and β functions to leading order. To non-leading order we formally evaluate and renormalise the effective potential. In three dimensions we also calculate the β function to \(0\left( {\frac{1}{N}} \right)\) . We show that it has a non-trivial fixed point which corresponds to a phase transition. This phenomenon persists beyond the leading order. The vacuum states are also unchanged by the nonleading order corrections.     

Birkhoff’s Polytope and Unistochastic Matrices,N = 3 and N = 4

The set of bistochastic or doubly stochastic N×N matrices is a convex set called Birkhoff’s polytope, which we describe in some detail. Our problem is to characterize the set of unistochastic matrices as a subset of Birkhoff’s polytope. For N=3 we present fairly complete results. For N=4 partial results are obtained. An interesting difference between the two cases is that there is a ball of unistochastic matrices around the van der Waerden matrix for N=3, while this is not the case for N=4.     

Circular Dichroism and Conformation of Bilirubin Bis N,N, N-Trimethyl α-Phenethylammonium Salts

Analysis of the bisignate circular dichroism spectra of bilirubin-IXα bis-propionate salts of (S)-(-)-N, N, N-trimethyl α-phenethylammonium hydroxide reveals a preference in CHC1₃, (CH₃)₂ CO and CH₃ CN solvents for folded conformations in which the propionate groups are intramolecularly H-bonded to the opposing pyrromethenone units.     

Holography beyond conformal invariance and AdS isometry?

Journal of Experimental and Theoretical Physics - We suggest that the principle of holographic duality be extended beyond conformal invariance and AdS isometry. Such an extension is based on a...     

Gibbs’ paradox according to Gibbs and slightly beyond

ABSTRACT

The so-called Gibbs’ paradox is a paradigmatic narrative illustrating the necessity to account for the N! ways of permuting N identical particles when summing over microstates. Yet, there exist some mixing scenarios for which the expected thermodynamic outcome depends on the viewpoint one chooses to justify this combinatorial term. After a brief summary on Gibbs’ paradox and what is the standard rationale used to justify its resolution, we will allow ourself to question from a historical standpoint whether the Gibbs’ paradox has actually anything to do with Gibbs’ work. In so doing, we also aim at shedding a new light with regards to some of the theoretical claims surrounding its resolution. We will then turn to the statistical thermodynamics of discrete and continuous mixtures and introduce the notion of composition entropy to characterise these systems. This will enable us to address, in a certain sense, a ‘curiosity” pointed out by Gibbs in a paper published in 1876. Finally, we will finish by proposing a connexion between the results we propose and a recent extension of the Landauer bound regarding the minimum amount of heat to be dissipated to reset one bit of memory.     

Theoretical study on structures of Ga3N, GaN3, Ga3N2 and Ga2N3 clusters

The structures of Ga_3N, GaN_3, Ga_3N_2 and Ga_2N_3 clusters are studied using the full-potential linear-muffin-tin-orbital molecular dynamics (FP-LMTO MD) method. Four structures for Ga_3 N, five structures for GaN_3, nine structures for Ga_3N_2 and nine structures for Ga_2N_3 have been obtained. The most stable structures of these clusters are planar ones. A strong dominance of the N－-N bond over the Ga－-N and Ga－-Ga bonds appears to control the structural skeletons, supporting the previous result obtained by Kandalam and co-workers. The most stable structures of these small GaN clusters displayed semiconductor-like properties through the calculation of the HOMO－LUMO gaps.     

Infrared Absorption Study of Some Cyclic Ureas,Cyclic Thioureas and Their N,N′-Dialkyl Derivatives

Abstract

In his communication on the detection limits for thermal emission spectroscopy of metallic species in flame media, Fassel (¹) attacks our previous statement that detection limits for Al, Be and Mo were available only for turbulent oxygen-supported hydrogen or acetylene flames. It should be borne in mind that he was referring to a preliminary communication (²) which naturally does not carry an extensive bibliography. It should also be noted that we were concerned, in context, with a comparison of the separated flame with conventional flames, not with highly unconventional flames such as those to which he refers. Whilst the point with which he takes issue was a very minor one, incorporated in our preliminary communication mainly as an “aside”, we firmly disagree with his observation. The flame he refers to (³) (⁴) is, in fact, a diluted oxy-acetylene flame which is supported by venting some air (and therefore nitrogen) to dilute the fuel-oxygen mixture. Fassel's communication (¹) erroneously refers to this as a 'premixed oxy-acetylene flame', whereas elsewhere (⁵) it is described more correctly as an oxygen-nitrogen-acetylene flame. The burner he long-pathlength carbonaceous flames (¹⁰). They also allow more sensitive molecular emission spectroscopy of sulphur in an air-hydrogen flame (¹¹), etc. We hope that this unfortunate correspondence will not distract attention from the main issue of our previous or previous preliminary communication on the separated nitrous oxide-acetylene flime.     

Pressure and temperature effects on the Γ, N and L-phonons in zirconium

Abstract

The effective potentials for the E_2g,-phonon at the T point of the Brillouin zone of hep Zr, the transverse N- and longitudinal L-phonons of bcc Zr are calculated for different pressures by the “frozen phonon” method. The temperature and pressure dependences of the phonon frequencies are studied within the framework of a modified pseudo-harmonic approximation. The results obtained are in good agreement with the experimental ones. The stability of the hep, bec and ω phases of zirconium at different temperatures and pressures is discussed.     

Viscoelasticity and morphology of an organic hybrid of chlorinated polyethylene and N,N′-dicyclohexyl-2-benzothiazolyl sulfenamide

The viscoelasticity and morphology of an organic hybrid of chlorinated polyethylene (CPE) and N,N′-dicyclohexyl-2-benzothiazolyl sulfenamide (DBS) were studied by means of tensile and shear complex modulus and differential scanning calorimetry (DSC) analysis. Tensile and shear loss modulus (E″ and G″), which are shown as indexes of vibration damping performance, showed one peak corresponding to the glass transition. The peak maximum values (E″_max and G″_max)increased in proportion to DBS content ( _DBS) and the slope of E″_max against _DBS became steep above a certain DBS content, i.e. the critical DBS content ( _c). A high damping material was obtained by the addition of DBS, especially when DBS content was higher than _c. These increases in loss moduli below and above _c are caused by the interaction between CPE and DBS molecules and the friction between DBS molecules, respectively. It was found that CPE/DBS is a compatible blend at all DBS contents from the analysis of the glass transition temperature with DSC. Furthermore, the influence of chlorine content in CPE on those characteristics was investigated. Higher chlorine content led to lower _c, a decrease in E″ below _c and an increase in E″ above _c. These results are due to the increase in the number of dichloromethylene units (CCl₂), which reduces the α-hydrogen atom in CPE.     

Superconductivity,Pair Density Wave,and Néel Order in Cuprates

We investigate in underdoped cuprates possible coexistence of the superconducting order at zero momentum and pair density wave(PDW) at momentum Q=(π,π) in the presence of a Neel order.By symmetry,the d-wave uniform singlet pairing dS₀ can coexist with the d-wave triplet PDW dT_Q,and the p-wave singlet PDW pS_Q can coexist with the p-wave uniform triplet pT₀.At half filling,we find that the novel pS_Q+pT₀ state is energeticall.y more ...     

Hyperfine interactions of polarized β-emitting12B and12N in Si,Ge, and GaP

Using a nuclear reaction, the polarized short-lived -emitters¹²B and¹²N were implanted into Si, Ge, and GaP crystals. Hyperfine fields were studied via both NMR techniques and an external magnetic holding field H_ext on-off techniques in an H_ext range 0–8 kG and a temperature range 100–1000 K. No significant NMR signal was observed between 2 and 30 MHz for¹²N in Si and Ge despite maintenance of 60% polarization at T100 K and H_ext>4 kG, whereas for¹²B in Si at T>800 K almost full polarization was found at the Larmor frequency.