18279063
On memory in exponentially expanding spaces
A bstractWe examine the degree to which fluctuating dynamics on exponentially expanding spaces remember initial conditions. In de Sitter space, the global late-time configuration of a free scalar field always contains information about early fluctuations. By contrast, fluctuations near the boundary of Euclidean Anti-de Sitter may or may not remember conditions in the center, with a transition at Δ = d/2. We connect these results to literature about statistical mechanics on trees and make contact with the observation by Anninos and Denef that the configuration space of a massless dS field exhibits ultrametricity. We extend their analysis to massive fields, finding that preference for isosceles triangles persists as long as Δ−< d/4.
67837531
Hawking-Page transition in holographic massive gravity
We study the Hawking-Page transition in a holographic model of field theories with momentum dissipation. We find that the deconfinement temperature strictly decreases as momentum dissipation is increased. For sufficiently strong momentum dissipation, the critical temperature goes to zero, indicating a zero-temperature deconfinement transition in the dual field theory.
18134055
Localized shocks
A bstractWe study products of precursors of spatially local operators, Wxntn⋅⋅⋅Wx1t1$$ {W_x}_{{}_n}(tn)\cdot \cdot \cdot {W}_{x_1}\left({t}_1\right) $$, where Wx(t) = e− iHtWxeiHt. Using chaotic spin-chain numerics and gauge/gravity duality, we show that a single precursor fills a spatial region that grows linearly in t. In a lattice system, products of such operators can be represented using tensor networks. In gauge/gravity duality, they are related to Einstein-Rosen bridges supported by localized shock waves. We find a geometrical correspondence between these two descriptions, generalizing earlier work in the spatially homogeneous case.
953790
The (t,He3) and (He3, t) reactions as probes of Gamow-Teller strength
It is shown via a study on a Mg-26 target that the (t,He-3) reaction at 115 MeV/nucleon reaction is an accurate probe for extracting Gamow-Teller transition strengths. To do so, the data are complemented by results from the Mg-26(He-3, t) reaction at 140 MeV/nucleon that allows for a comparison of T=2 analog states excited via the mirror reactions. Extracted Gamow-Teller strengths from Mg-26(t,He-3) and Mg-26(He-3, t) are compared with those from Mg-26(d,He-2) and Mg-26(p,n) studies, respectively. A good correspondence is found, indicating probe independence of the strength extraction. Furthermore, we test shell-model calculations using the new USD-05B interaction in the sd-model space and show that it reproduces the experimental Gamow-Teller strength distributions well. In anticipation of further (t,He-3) experiments on medium-heavy nuclei aimed at determining weak-interaction rates of relevance for stellar evolution, a second goal of this work is to improve the understanding of the (t,He-3) and (He-3, t) reaction mechanisms at intermediate energies because detailed studies are scarce. The distorted-wave Born approximation is employed, taking into account the composite structures of the He-3 and triton particles. The reaction model provides the means to explain systematic uncertainties at the 10%-20% level in the extraction of Gamow-Teller strengths as being because of interference between Gamow-Teller Delta L=0,Delta S=1 and Delta L=2,Delta S=1 amplitudes that both contribute to transitions from 0(+) to 1(+) states.
18200063
Masers as Probes of Massive Star Formation in the Nuclear Disk
Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301 USAemail: bwhitney@spacescience.orgAbstract.OH(1720 MHz) and methanol masers are now recognized to be excellent probes of theinteractions of supernova remnants with molecular clouds and tracers of massive star formation,respectively. To better understand the nature of star formation activity in the central regionof the Galaxy, we have used these two classes of masers combined with the IRAC and MIPSdata to study prominent sites of ongoing star formation in the nuclear disk. The nuclear diskis characterized by massive GMCs with elevated gas temperatures, compared to their dusttemperatures. We note an association between methanol masers and a class of mid-infrared“green sources”. These highly embedded YSOs show enhanced 4.5µm emission due to excitedmolecular lines.The distribution of methanol masers and supernova remnants suggest a low eﬃciency of starformation (with the exception of Sgr B2), which we believe is due to an enhanced ﬂux of cosmicray electrons impacting molecular clouds in the nuclear disk. We also highlight the importanceof cosmic rays in their ability to heat molecular clouds, and thus increase the gas temperature.Keywords. Masers, supernova remnants, cosmic rays.
125696689
High-resolution study of Gamow-Teller transitions via the Fe-54(He-3, t)Co-54 reaction
119068583
Inclusive pion double charge exchange in 4He at intermediate energies
A systematic experimental study of inclusive pion double charge exchange in 4He has been undertaken. The reaction 4He(pi+,pi-)4p was observed at incident energies 120, 150, 180, 240 and 270 MeV; the 4He(pi-,pi+)4n reaction was observed at incident energies 180 and 240 MeV. At each incident energy, the doubly differential cross section was measured at three to five outgoing pion laboratory angles between 25 deg and 130 deg. At each angle, cross sections were measured over the range of outgoing pion energies from 10 MeV up to the kinematic limit for the reaction in which the final state consists of the oppositely charged pion plus four free nucleons. 
The spectra of outgoing pions are strikingly different from those observed for the inclusive double charge exchange reaction in heavier nuclei, but resemble those observed in the (pi-,pi+) reaction in 3He. The forward-angle spectra in the 3He and 4He reactions exhibit a prominent peak at high outgoing pion energies. Interpretation of the peaks in 3He (4He) as a three- (four-)nucleon resonance is ruled out by kinematic analysis. The results of a calculation, wherein the double charge exchange reaction is assumed to proceed as two sequential single charge exchange interactions, suggest that the high-energy peak is naturally explained by this double scattering mechanism. Non-static treatment of the pi-N interactions and the inclusion of nuclear binding effects appear to be important in reproducing the shape of the energy spectra at forward angles.
125276782
Search for isovector giant monopole resonances via the Sn-124(He-3,tn) reaction
The (He-3,t) reaction on Sn-124 at E(He-3)=199 MeV and the subsequent decay by neutron emission at backward angles were studied in an attempt to distinguish isovector monopole strength (spin-flip and non-spin-flip) at excitation energies above 25 MeV from the nonresonant continuum. The present approach is based on the assumption that a large fraction of the contributions to the continuum result from quasifree processes and breakup-pickup processes which leave the nucleus in low-lying excited states below the threshold for neutron emission. It was found, however, that even at high "apparent" excitation energies (above 30 MeV) the branching ratio for decay by neutrons was as high as similar to 50%, indicating that a large part of the nonresonant continuum may not be due to quasifree processes involving valence neutrons only. No evidence for monopole strength at high excitation energies was found, although the experiment had sufficient sensitivity and accuracy to detect isovector monopole strength based on theoretical predictions calculated in the framework of normal-mode collective excitations and the distorted-wave Born approximation.