Quantum Gravitational Corrections To The Nonrelativistic Scattering Potential Of Two Masses,
2011
University of Massachusetts Amherst
Quantum Gravitational Corrections To The Nonrelativistic Scattering Potential Of Two Masses, Nej Bjerrum-Bohr, Jf Donoghue, Br Holstein
Barry R Holstein
We treat general relativity as an effective field theory, obtaining the full nonanalytic component of the scattering matrix potential to one-loop order. The lowest order vertex rules for the resulting effective field theory are presented and the one-loop diagrams which yield the leading nonrelativistic post-Newtonian and quantum corrections to the gravitational scattering amplitude to second order in G are calculated in detail. The Fourier transformed amplitudes yield a nonrelativistic potential and our result is discussed in relation to previous calculations. The definition of a potential is discussed as well, and we show that the ambiguity of the potential under coordinate …
Chiral Anomaly And Eta-Eta ' Mixing,
2011
University of Massachusetts Amherst
Chiral Anomaly And Eta-Eta ' Mixing, Ep Venugopal, Br Holstein
Barry R Holstein
We determine the η-η′ mixing angle via a procedure relatively independent of theoretical assumptions by simultaneously fitting η,η′ reactions involving the anomaly η,η′→γγ, π+π-γ. We extract reasonably precise renormalized values of the octet and singlet pseudoscalar decay constants F8, F0, as well as the mixing angle θ.
Quantum Corrections To The Schwarzschild And Kerr Metrics,
2011
University of Massachusetts Amherst
Quantum Corrections To The Schwarzschild And Kerr Metrics, Nej Bjerrum-Bohr, Jf Donoghue, Br Holstein
Barry R Holstein
No abstract provided.
Overview Of Hadronic Parity Violation,
2011
University of Massachusetts Amherst
Overview Of Hadronic Parity Violation, Br Holstein
Barry R Holstein
The subject of hadronic parity violation is nearly fifty years old, but a good deal of uncertainty remains, despite many efforts both theoretical and experimental. A brief summary of the field is presented and a plan is proposed for new experimental work which, when combined with a new theoretical tack based on effective field theory, should lead to resolution of the present difficulties.
An Eft For The Weak Lambda N Interaction,
2011
University of Massachusetts Amherst
An Eft For The Weak Lambda N Interaction, A Parreno, C Bennhold, Br Holstein
Barry R Holstein
The nonleptonic weak |ΔS|=1 ΛN interaction, responsible for the dominant, nonmesonic decay of all but the lightest hypernuclei, is studied in the framework of an effective field theory. The long-range physics is described through tree-level exchange of the SU(3) Goldstone bosons (π and K), while the short-range potential is parametrized in terms of lowest-order contact terms obtained from the most general non-derivative local four-fermion interaction. Fitting to available weak hypernuclear decay rates for 5ΛHe, 11ΛB and 12ΛC yields reasonable values for the low-energy constants.
The Delta-S=2 Matrix Element For K0-Kbar0 Mixing,
2011
University of Massachusetts Amherst
The Delta-S=2 Matrix Element For K0-Kbar0 Mixing, Jf Donoghue, Eugene Golowich, Br Holstein
Barry R Holstein
We use SU(3) and PACAC to relate the ΔS = 2 matrix element Image Full-size image (1K) to experimental information on the Image contribution to K → 2π. Our results is Image which is about 33% of the vacuum insertion value.
Chiral Corrections To The Vector And Axial Couplings Of Quarks And Baryons,
2011
University of Massachusetts Amherst
Chiral Corrections To The Vector And Axial Couplings Of Quarks And Baryons, A Faessler, T Gutsche, Br Holstein, Ve Lyubovitskij
Barry R Holstein
We calculate chiral corrections to the semileptonic vector and axial quark coupling constants using a manifestly Lorentz covariant chiral quark approach up to order O(p4) in the two- and three-flavor pictures. These couplings are then used in the evaluation of the corresponding couplings which govern the semileptonic transitions between octet baryon states. In the calculation of baryon matrix elements we use a general ansatz for the spatial form of the quark wave function, without referring to a specific realization of hadronization and confinement of quarks in baryons. Matching the physical amplitudes calculated within our approach to the model-independent predictions of …
Components Of A Chiral Coefficient,
2011
University of Massachusetts Amherst
Components Of A Chiral Coefficient, Jf Donoghue, Br Holstein
Barry R Holstein
One of the coefficients that parametrizes the chiral Lagrangian of QCD is expressible in terms of a sum rule for which the integrand is known from experiment. We confront two model calculations of this coefficient with the behavior of the data. The model related to vector dominance reproduces the sumrule behavior very well, whereas a one-loop chiral quark model calculation fails badly. The sum rule allows one to identify those ingredients which are needed to make the quark method more realistic.
Systematic 1/M Expansion For Spin 3/2 Particles In Baryon Chiral Perturbation Theory,
2011
University of Massachusetts Amherst
Systematic 1/M Expansion For Spin 3/2 Particles In Baryon Chiral Perturbation Theory, Tr Hemmert, Br Holstein, J Kambor
Barry R Holstein
Starting from a relativistic formulation of the pion-nucleon-delta system, the most general structure of 1/M corrections for a heavy baryon chiral lagrangian including spin 3/2 resonances is given. The heavy components of relativistic nucleons and delta fields are integrated out and their contributions to the next-to-leaing order lagrangians are constructed explicitly. The effective theory obtained admits a systematic expansion in terms of soft momenta, the pion mass $m_\pi$ and the delta-nucleon mass difference $\Delta$. As an application, we consider neutral pion photoproduction at threshold to third order in this small scale expansion.
Chiral Symmetry And The Large-Nc Limit In Kl4 Decays,
2011
University of Massachusetts Amherst
Chiral Symmetry And The Large-Nc Limit In Kl4 Decays, C Riggenbach, J Gasser, Jf Donoghue, Br Holstein
Barry R Holstein
The treatment of kaon decays using chiral symmetry yields predictions for thè form factors in K→ππeν. In addition, the large-Nc limit of QCD implies that a particular combination of low-energy constants should be suppressed. We present the chiral predictions for Kl4 decays at next-to-leading order in the energy expansion. By combining the phenomenologies of Kl4 and ππ scattering, we test these predictions and provide a determination of the parameters in the chiral Lagrangian of QCD.
Long-Distance Chiral Contributions To The Kl-Ks Mass Difference,
2011
University of Massachusetts Amherst
Long-Distance Chiral Contributions To The Kl-Ks Mass Difference, Jf Donoghue, Eugene Golowich, Br Holstein
Barry R Holstein
We use chiral symmetry to calculate the very long distance contributions to the KL–KS mass difference. We determine that the dominant effect arises from the two-pion dispersive contribution, which by itself produces a large result comparable to or greater than the experimental mass difference (with the correct sign). Some contributions from intermediate distance are also estimated and could be significant. These conclusions reinforce the need, first pointed out by Wolfenstein, to include an additive parameter to account for the long distance contributions in phenomenological studies of the KL–KS mass difference. This parameter may be determined from the data if the …
Limits On The Time Variation Of The Fermi Constant G_F Based On Type Ia Supernova Observations,
2011
University of South Carolina
Limits On The Time Variation Of The Fermi Constant G_F Based On Type Ia Supernova Observations, Alejandro Ferrero, Brett David Altschul
Faculty Publications
The light curve of a type Ia supernova decays at a rate set by the beta-decay lifetimes of the 56N iand Co56 produced in the explosion. This makes such a light curve sensitive to the value of the Fermi constant GF at the time of the supernova. Using data from the CfA Supernova Archive, we measure the dependence of the light curve decay rate on redshift and place a bound on the time variation of GF of |(dG_F/dt)/G_F| < 10-9 / y1.
Human Disease Classification In The Postgenomic Era: A Complex Systems Approach To Human Pathobiology,
2011
Brigham and Women's Hospital and Harvard Medical School
Human Disease Classification In The Postgenomic Era: A Complex Systems Approach To Human Pathobiology, Joseph Loscalzo, Isaac Kohane, Albert-László Barabási
Albert-László Barabási
Contemporary classification of human disease derives from observational correlation between pathological analysis and clinical syndromes. Characterizing disease in this way established a nosology that has served clinicians well to the current time, and depends on observational skills and simple laboratory tools to define the syndromic phenotype. Yet, this time-honored diagnostic strategy has significant shortcomings that reflect both a lack of sensitivity in identifying preclinical disease, and a lack of specificity in defining disease unequivocally. In this paper, we focus on the latter limitation, viewing it as a reflection both of the different clinical presentations of many diseases (variable phenotypic expression), …
Emerging Behavior In Electronic Bidding,
2011
Seoul National University
Emerging Behavior In Electronic Bidding, I. Yang, H. Jeong, B. Kahng, A.-L. Barabási
Albert-László Barabási
We characterize the statistical properties of a large number of agents on two major online auction sites. The measurements indicate that the total number of bids placed in a single category and the number of distinct auctions frequented by a given agent follow power-law distributions, implying that a few agents are responsible for a significant fraction of the total bidding activity on the online market. We find that these agents exert an unproportional influence on the final price of the auctioned items. This domination of online auctions by an unusually active minority may be a generic feature of all online …
Spectra Of "Real-World" Graphs: Beyond The Semicircle Law,
2011
Eötvös University
Spectra Of "Real-World" Graphs: Beyond The Semicircle Law, Illés J. Farkas, Imre Derényi, Albert-László Barabási, Tamás Vicsek
Albert-László Barabási
Many natural and social systems develop complex networks that are usually modeled as random graphs. The eigenvalue spectrum of these graphs provides information about their structural properties. While the semicircle law is known to describe the spectral densities of uncorrelated random graphs, much less is known about the spectra of real-world graphs, describing such complex systems as the Internet, metabolic pathways, networks of power stations, scientific collaborations, or movie actors, which are inherently correlated and usually very sparse. An important limitation in addressing the spectra of these systems is that the numerical determination of the spectra for systems with more …
Dynamics Of Complex Systems: Scaling Laws For The Period Of Boolean Networks,
2011
University of Notre Dame
Dynamics Of Complex Systems: Scaling Laws For The Period Of Boolean Networks, Réka Albert, Albert-László Barabási
Albert-László Barabási
Boolean networks serve as models for complex systems, such as social or genetic networks, where each vertex, based on inputs received from selected vertices, makes its own decision about its state. Despite their simplicity, little is known about the dynamical properties of these systems. Here we propose a method to calculate the period of a finite Boolean system, by identifying the mechanisms determining its value. The proposed method can be applied to systems of arbitrary topology, and can serve as a roadmap for understanding the dynamics of large interacting systems in general.
Separating The Internal And External Dynamics Of Complex Systems,
2011
University of Notre Dame
Separating The Internal And External Dynamics Of Complex Systems, M. Argollo De Menezes, A.-L. Barabási
Albert-László Barabási
The observable behavior of a complex system reflects the mechanisms governing the internal interactions between the system’s components and the effect of external perturbations. Here we show that by capturing the simultaneous activity of several of the system’s components we can separate the internal dynamics from the external fluctuations. The method allows us to systematically determine the origin of fluctuations in various real systems, finding that while the Internet and the computer chip have robust internal dynamics, highway and Web traffic are driven by external demand. As multichannel measurements are becoming the norm in most fields, the method could help …
Dynamics Of Information Access On The Web,
2011
University of Notre Dame
Dynamics Of Information Access On The Web, Z. Dezsö, E. Almaas, A. Lukács, B. Rácz, I. Szakadát, A.-L. Barabási
Albert-László Barabási
While current studies on complex networks focus on systems that change relatively slowly in time, the structure of the most visited regions of the web is altered at the time scale from hours to days. Here we investigate the dynamics of visitation of a major news portal, representing the prototype for such a rapidly evolving network. The nodes of the network can be classified into stable nodes, which form the timeindependent skeleton of the portal, and news documents. The visitations of the two node classes are markedly different, the skeleton acquiring visits at a constant rate, while a news document’s …
Percolation In Directed Scale-Free Networks,
2011
Bar-Ilan University, Ramat Gan
Percolation In Directed Scale-Free Networks, N. Schwartz, R. Cohen, D. Ben-Avraham, A.-L. Barabási, S. Havlin
Albert-László Barabási
Many complex networks in nature have directed links, a property that affects the network’s navigability and large-scale topology. Here we study the percolation properties of such directed scale-free networks with correlated in and out degree distributions. We derive a phase diagram that indicates the existence of three regimes, determined by the values of the degree exponents. In the first regime we regain the known directed percolation mean field exponents. In contrast, the second and third regimes are characterized by anomalous exponents, which we calculate analytically. In the third regime the network is resilient to random dilution, i.e., the percolation threshold …
Topology Of Evolving Networks: Local Events And Universality,
2011
University of Notre Dame
Topology Of Evolving Networks: Local Events And Universality, Réka Albert, Albert-László Barabási
Albert-László Barabási
Networks grow and evolve by local events, such as the addition of new nodes and links, or rewiring of links from one node to another. We show that depending on the frequency of these processes two topologically different networks can emerge, the connectivity distribution following either a generalized power law or an exponential. We propose a continuum theory that predicts these two regimes as well as the scaling function and the exponents, in good agreement with numerical results. Finally, we use the obtained predictions to fit the connectivity distribution of the network describing the professional links between movie actors.
