The B-L/Electroweak Hierarchy in Smooth Heterotic Compactifications

E8 X E8 heterotic string and M-theory, when appropriately compactified, can give rise to realistic, N=1 supersymmetric particle physics. In particular, the exact matter spectrum of the MSSM, including three right-handed neutrino supermultiplets, one per family, and one pair of Higgs-Higgs conjugate superfields is obtained by compactifying on Calabi-Yau manifolds admitting specific SU(4) vector bundles. These "heterotic standard models" have the SU(3)_{C} X SU(2)_{L} X U(1)_{Y} gauge group of the standard model augmented by an additional gauged U(1)_{B-L}. Their minimal content requires that the B-L gauge symmetry be spontaneously broken by a vacuum expectation value of at least one right-handed sneutrino. In a previous paper, we presented the results of a renormalization group analysis showing that B-L gauge symmetry is indeed radiatively broken with a B-L/electroweak hierarchy of O(10) to O(10^{2}). In this paper, we present the details of that analysis, extending the results to include higher order terms in tan[beta]^{-1} and the explicit spectrum of all squarks and sleptons.Comment: 60 pages, 6 figure

Helioseismology of Pre-Emerging Active Regions II: Average Emergence Properties

We report on average subsurface properties of pre-emerging active regions as compared to areas where no active region emergence was detected. Helioseismic holography is applied to samples of the two populations (pre-emergence and without emergence), each sample having over 100 members, which were selected to minimize systematic bias, as described in Leka et al. We find that there are statistically significant signatures (i.e., difference in the means of more than a few standard errors) in the average subsurface flows and the apparent wave speed that precede the formation of an active region. The measurements here rule out spatially extended flows of more than about 15 m/s in the top 20 Mm below the photosphere over the course of the day preceding the start of visible emergence. These measurements place strong constraints on models of active region formation.Comment: 15 pages, 10 figures, ApJ (published

Parallel updating cellular automaton models of driven diffusive Frenkel-Kontorova-type systems

Three cellular automaton (CA) models of increasing complexity are introduced to model driven diffusive systems related to the generalized Frenkel-Kontorova (FK) models recently proposed by Braun [Phys.Rev.E58, 1311 (1998)]. The models are defined in terms of parallel updating rules. Simulation results are presented for these models. The features are qualitatively similar to those models defined previously in terms of sequentially updating rules. Essential features of the FK model such as phase transitions, jamming due to atoms in the immobile state, and hysteresis in the relationship between the fraction of atoms in the running state and the bias field are captured. Formulating in terms of parallel updating rules has the advantage that the models can be treated analytically by following the time evolution of the occupation on every site of the lattice. Results of this analytical approach are given for the two simpler models. The steady state properties are found by studying the stable fixed points of a closed set of dynamical equations obtained within the approximation of retaining spatial correlations only upto two nearest neighboring sites. Results are found to be in good agreement with numerical data.Comment: 26 pages, 4 eps figure

String Method for the Study of Rare Events

We present a new and efficient method for computing the transition pathways, free energy barriers, and transition rates in complex systems with relatively smooth energy landscapes. The method proceeds by evolving strings, i.e. smooth curves with intrinsic parametrization whose dynamics takes them to the most probable transition path between two metastable regions in the configuration space. Free energy barriers and transition rates can then be determined by standard umbrella sampling technique around the string. Applications to Lennard-Jones cluster rearrangement and thermally induced switching of a magnetic film are presented.Comment: 4 pages, 4 figure

When contrasting polarity, the Dutch use particles, Germans intonation

This study compares how Dutch and German, two closely related languages, signal a shift from a negative to a positive polarity in two contexts, when contrasting the polarity relative to a different topic situation (In my picture the man washes the car following after In my picture the man does not wash the car, henceforth polarity contrast) and when correcting the polarity of a proposition (The man washes the car following after The man does not wash the car, henceforth polarity correction). Production data show that in both contexts German speakers produced Verum focus (i.e., a high-falling pitch accent on the finite verb), while Dutch speakers mostly used the accented affirmative particle wel. This shows that even lexically and syntactically close languages behave differently when it comes to signalling certain pragmatic functions. Furthermore, we found that in polarity correction contexts, both affirmative particles and Verum focus were realized with stronger prosodic prominence. This difference was found in both languages and might be due to a secondary (syntagmatic) effect of the information structure of the utterance (absence or presence of a contrastive topic)

Intonational means to mark verum focus in German and French

German and French differ in a number of aspects. Regarding the prosody-pragmatics interface, German is said to have a direct focus-to-accent mapping, which is largely absent in French – owing to strong structural constraints. We used a semi-spontaneous dialogue setting to investigate the intonational marking of Verum Focus, a focus on the polarity of an utterance in the two languages (e.g. the child IS tearing the banknote as an opposite claim to the child is not tearing the banknote). When Verum Focus applies to auxiliaries, pragmatic aspects (i.e. highlighting the contrast) directly compete with structural constraints (e.g. avoiding an accent on phonologically weak elements such as monosyllabic function words). Intonational analyses showed that auxiliaries were predominantly accented in German, as expected. Interestingly, we found a high number of (as yet undocumented) focal accents on phrase-initial auxiliaries in French Verum Focus contexts. When French accent patterns were equally distributed across information structural contexts, relative prominence (in terms of peak height) between initial and final accents was shifted towards initial accents in Verum Focus compared to non-Verum Focus contexts. Our data hence suggest that French also may mark Verum Focus by focal accents but that this tendency is partly overridden by strong structural constraints

Can quarkonia survive deconfinement ?

We study quarkonium correlators and spectral functions at zero and finite temperature in QCD with only heavy quarks using potential models combined with perturbative QCD. First, we show that this approach can describe the quarkonium correlation function at zero temperature. Using a class of screened potentials based on lattice calculations of the static quark-antiquark free energy we calculate spectral functions at finite temperature. We find that all quarkonium states, with the exception of the $1S$ bottomonium, dissolve in the deconfined phase at temperatures smaller than $1.5T_c$, in contradiction with the conclusions of recent studies. Despite this the temperature dependence of the quarkonium correlation functions calculated on the lattice is well reproduced in our model. We also find that even in the absence of resonances the spectral function at high temperatures is significantly enhanced over the spectral function corresponding to free quark antiquark propagation.Comment: Version accepted in Phys. Rev. D, 20 pages, 25 figure

Unusual Ground State Properties of the Kondo-Lattice Compound Yb2Ir3Ge5

We report sample preparation, structure, electrical resistivity, magnetic susceptibility and heat capacity studies of a new compound Yb$_2$Ir$_3$Ge$_5$. We find that this compound crystallizes in an orthorhombic structure with a space group PMMN unlike the compound Ce$_2$Ir$_3$Ge$_5$ which crystallizes in the tetragonal IBAM (U$_2$Co$_3$Si$_5$ type) structure. Our resistivity measurements indicate that the compound Yb$_2$Ir$_3$Ge$_5$ behaves like a typical Kondo lattice system with no ordering down to 0.4 K. However, a Curie-Weiss fit of the inverse magnetic susceptibility above 100 K gives an effective moment of only 3.66 $\mu$$_B$ which is considerably less than the theoretical value of 4.54 $\mu$$_B$ for magnetic Yb$^3+$ ions. The value of $\theta_{P}$ = -15.19 K is also considerably higher indicating the presence of strong hybridization. An upturn in the low temperature heat capacity gives an indication that the system may order magnetically just below the lowest temperature of our heat capacity measurements (0.4 K). The structure contains two sites for Yb ions and the present investigation suggests that Yb may be trivalent in one site while it may be significantly lower (close to divalent) in the other.Comment: 9 pages, 4 figures. submitted to Phys. Rev.