27,806 research outputs found
A Simple Technique for Predicting High-Redshift Galaxy Evolution
We show that the ratio of galaxies' specific star formation rates (SSFRs) to
their host halos' specific mass accretion rates (SMARs) strongly constrains how
the galaxies' stellar masses, specific star formation rates, and host halo
masses evolve over cosmic time. This evolutionary constraint provides a simple
way to probe z>8 galaxy populations without direct observations. Tests of the
method with galaxy properties at z=4 successfully reproduce the known evolution
of the stellar mass--halo mass (SMHM) relation, galaxy SSFRs, and the cosmic
star formation rate (CSFR) for 5<z<8. We then predict the continued evolution
of these properties for 8<z<15. In contrast to the non-evolution in the SMHM
relation at z<4, the median galaxy mass at fixed halo mass increases strongly
at z>4. We show that this result is closely linked to the flattening in galaxy
SSFRs at z>2 compared to halo specific mass accretion rates; we expect that
average galaxy SSFRs at fixed stellar mass will continue their mild evolution
to z~15. The expected CSFR shows no breaks or features at z>8.5; this
constrains both reionization and the possibility of a steep falloff in the CSFR
at z=9-10. Finally, we make predictions for stellar mass and luminosity
functions for the James Webb Space Telescope (JWST), which should be able to
observe one galaxy with M* > ~10^8 Msun per 10^3 Mpc^3 at z=9.6 and one such
galaxy per 10^4 Mpc^3 at z=15.Comment: Revised to include JWST luminosity functions, matching accepted
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Time-dependent Real-space Renormalization-Group Approach: application to an adiabatic random quantum Ising model
We develop a time-dependent real-space renormalization-group approach which
can be applied to Hamiltonians with time-dependent random terms. To illustrate
the renormalization-group analysis, we focus on the quantum Ising Hamiltonian
with random site- and time-dependent (adiabatic) transverse-field and
nearest-neighbour exchange couplings. We demonstrate how the method works in
detail, by calculating the off-critical flows and recovering the ground state
properties of the Hamiltonian such as magnetization and correlation functions.
The adiabatic time allows us to traverse the parameter space, remaining near-to
the ground state which is broadened if the rate of change of the Hamiltonian is
finite. The quantum critical point, or points, depend on time through the
time-dependence of the parameters of the Hamiltonian. We, furthermore, make
connections with Kibble-Zurek dynamics and provide a scaling argument for the
density of defects as we adiabatically pass through the critical point of the
system
Unions, Bargaining and Strikes
Labor disputes are an intriguing feature of the landscape of industrialized economies. Economists have had a long-standing interest in formulating a framework for understanding and analyzing labor disputes. The development of noncooperative bargaining theory provided the tools for a theory of collective bargaining and labor disputes. A general aim of this theoretical development is to inform policy makers of the efficiency and equity effects associated with different labor laws and institutions that govern and shape the collective bargaining process. While this new literature is still evolving, it can already offer many insights into the interplay between policy and the bargaining process. In this chapter, we will provide a sketch of this new collective bargaining theory and illustrate its ability to aid in policy analysis. We will also relate the predictions of the model to existing empirical findings in the literature.Unions, Bargaining, Strikes, Collective Bargaining
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