16376745
Einstein-Podolsky-Rosen correlations of ultracold atomic gases.
We demonstrate that collective continuous variables of two species of trapped ultracold bosonic gases can be Einstein-Podolsky-Rosen-correlated (entangled) via inherent interactions between the species. We propose two different schemes for creating these correlations--a dynamical scheme and a static scheme analogous to two-mode squeezing in quantum optics. We quantify the correlations by using known measures of entanglement and study the effect of finite temperature on these quantum correlations.
4356427
The ‘Higgs’ amplitude mode at the two-dimensional superfluid/Mott insulator transition
Spontaneous symmetry breaking plays a key role in our understanding of nature. In relativistic quantum field theory, a broken continuous symmetry leads to the emergence of two types of fundamental excitation: massless Nambu–Goldstone modes and a massive ‘Higgs’ amplitude mode. An excitation of Higgs type is of crucial importance in the standard model of elementary particle physics, and also appears as a fundamental collective mode in quantum many-body systems. Whether such a mode exists in low-dimensional systems as a resonance-like feature, or whether it becomes overdamped through coupling to Nambu–Goldstone modes, has been a subject of debate. Here we experimentally find and study a Higgs mode in a two-dimensional neutral superfluid close to a quantum phase transition to a Mott insulating phase. We unambiguously identify the mode by observing the expected reduction in frequency of the onset of spectral response when approaching the transition point. In this regime, our system is described by an effective relativistic field theory with a two-component quantum field, which constitutes a minimal model for spontaneous breaking of a continuous symmetry. Additionally, all microscopic parameters of our system are known from first principles and the resolution of our measurement allows us to detect excited states of the many-body system at the level of individual quasiparticles. This allows for an in-depth study of Higgs excitations that also addresses the consequences of the reduced dimensionality and confinement of the system. Our work constitutes a step towards exploring emergent relativistic models with ultracold atomic gases.
14760942
A realistic unified gauge coupling from the micro-landscape of orbifold GUTs
Abstract We consider 5-dimensional supersymmetric field theories where supersymmetry is broken by the Scherk–Schwarz mechanism (or, equivalently, by the F-term VEV of the radion). In such models, the radion effective potential is calculable in terms of the 5d gauge coupling, the UV cutoff of the 5d field theory, and the field content. We provide simple, explicit formulae for the leading part of the two-loop effective potential. Our analysis applies in particular to 5d orbifold GUTs motivated by heterotic orbifold models. We focus on potentially realistic models of this type and make the additional assumption that the UV cutoff scale is identical with the strong-coupling scale of the 5d gauge theory. Given our stabilization mechanism, the 5d radius is now fixed in terms of the 5d gauge coupling and the field content of the model. This implies a prediction for the effective 4d gauge coupling only in terms of the field content of the model. Given the ‘micro-landscape’ provided by the different possible distributions of Standard Model fields between bulk and branes, we find a subset of models with a realistic unified gauge coupling. We also discuss two possibilities for the ‘uplifting’ of our SUSY-breaking AdS vacua: One is based on the possible presence of a weak warping, the other appeals to F-terms in an extra brane-localized SUSY-breaking sector.
122665147
De Sitter vacua and inflation in no-scale string models
This thesis studies the question of how de Sitter vacua and slow-roll inflation may be realized in string-motivated models. More specifically, we consider 4d N = 1 supergravity theories (without vector multiplets) with Kahler potentials which are ‘no-scale’ at leading order. Such theories frequently arise in the moduli sector of string compactifications. We discuss a condition on the scalar geometry (defined by the Kahler potential) and on the direction of supersymmetry breaking in the scalar manifold, which has to be met in order for the average of the masses of the sGoldstinos to be positive, and hence for metastable vacua to be possible. This condition also turns out to be necessary for the existence of trajectories admitting slow-roll inflation. Its implications for certain scalar manifolds which arise from Calabi-Yau string compactifications are discussed. In particular, for two-moduli models arising from compactifications of heteroticand type IIB string theory, a simple criterion on the intersection numbers needs to be satisfied for possible de Sitter phases to exist. In addition, we show that subleading corrections breaking the no-scale property may allow the condition on the scalar geometry to be fulfilled, even when it is violated at leading order. Finally, we develop a procedure to construct superpotentials for a given viable Kahler potential, such that the scalar potential has a realistic local minimum. We propose two-moduli models, with superpotentials which could arise from flux backgrounds and non-perturbative effects, which have a viable vacuum without employing subleading corrections or an uplifting sector.
15114914
De Sitter vacua in no-scale supergravities and Calabi-Yau string models
We perform a general analysis on the possibility of obtaining metastable vacua with spontaneously broken N = 1 supersymmetry and non-negative cosmological constant in the moduli sector of string models. More specifically, we study the condition under which the scalar partners of the Goldstino are non-tachyonic, which depends only on the Kahler potential. This condition is not only necessary but also sufficient, in the sense that all of the other scalar fields can be given arbitrarily large positive square masses if the superpotential is suitably tuned. We consider both heterotic and orientifold string compactifications in the large-volume limit and show that the no-scale property shared by these models severely restricts the allowed values for the 'sGoldstino' masses in the superpotential parameter space. We find that a positive mass term may be achieved only for certain types of compactifications and specific Goldstino directions. Additionally, we show how subleading corrections to the Kahler potential which break the no-scale property may allow to lift these masses.
8572469
Constructing de Sitter vacua in no-scale string models without uplifting
We develop a method for constructing metastable de Sitter vacua in N = 1 supergravity models describing the no-scale volume moduli sector of Calabi-Yau string compactifications. We consider both heterotic and orientifold models. Our main guideline is the necessary condition for the existence of metastable vacua coming from the Goldstino multiplet, which constrains the allowed scalar geometries and supersymmetry-breaking directions. In the simplest non-trivial case where the volume is controlled by two moduli, this condition simplifies and turns out to be fully characterised by the intersection numbers of the Calabi-Yau manifold. We analyse this case in detail and show that once the metastability condition is satisfied it is possible to reconstruct in a systematic way the local form of the superpotential that is needed to stabilise all the fields. We apply then this procedure to construct some examples of models where the superpotential takes a realistic form allowed by flux backgrounds and gaugino condensation effects, for which a viable vacuum arises without the need of invoking corrections to the Kahler potential breaking the no-scale property or uplifting terms. We finally discuss the prospects of constructing potentially realistic models along these lines.
122667645
First Observation of the Drip Line Nucleus 140Dy: Identification of a 7 Mu s K-isomer Populating the Ground State Band
A new $7 \ensuremath{\mu}\mathrm{s}$ isomer in the drip line nucleus ${}^{140}\mathrm{Dy}$ was selected from the products of the ${}^{54}\mathrm{Fe}$ $(315 \mathrm{MeV}{)+}^{92}\mathrm{Mo}$ reaction by a recoil mass spectrometer and studied with recoil-delayed $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidences. Five cascading $\ensuremath{\gamma}$ transitions were interpreted as the decay of an ${I}^{\ensuremath{\pi}}{=8}^{\ensuremath{-}}$ ${\ensuremath{\nu}{9/2}^{\ensuremath{-}}[514]\ensuremath{\bigotimes}\ensuremath{\nu}{7/2}^{+}[404]}$ K isomer $({T}_{1/2}=7.0(5) \ensuremath{\mu}\mathrm{s})$ via the ground-state band. The probability of proton emission from ${}^{141}\mathrm{Ho}$ to the ${0}^{+}$ ground state and to the ${2}^{+}$ excited state in ${}^{140}\mathrm{Dy}$ is discussed.
121758592
Fusion probability for neutron-rich radioactive Sn induced reactions
Evaporation residue cross sections for $$^{124,126,127,128}$$Sn+$$^{64}$$Ni and $$^{132}$$Sn+$$^{58}$$Ni have been measured to study the effects of neutron excess in neutron-rich radioactive nuclei on fusion. For the reactions with $$^{64}$$Ni, the fusion probability does not decrease with increasing neutron excess in Sn, contrary to the result of the stable beam Sn+Zr measurement. A comparison of the reduced evaporation residue cross sections for $$^{126}$$Sn+$$^{64}$$Ni and $$^{132}$$Sn+$$^{58}$$Ni, which make the same compound nucleus, shows that the fusion probability is indistinguishable for reactions involving the same atomic elements but different isotope combinations.
121184959
Search for inverse fission of uranium
There is a long-term interest in running the fission reaction backward, i.e., studying the 'inverse fission' of uranium. The recent availability of beams of n-rich fission fragments has stimulated interest in this endeavor. The purpose is to search for inverse fission in the reactions {sup 124,132}Sn + {sup 100}Mo. In the {sup 124}Sn + {sup 100}Mo reaction, evaporation residues were searched for using in-beam detection of evaporation residues, in-beam {alpha} spectroscopy, and post-irradiation {alpha} spectroscopy, while in the {sup 132}Sn + {sup 100}Mo reaction, the evaporation residue {sup 230}U was searched for using post-irradiation {alpha} spectroscopy. No evidence for the occurrence of the inverse fission reactions was found. The upper-limit cross section for the latter reaction is {approx}550 {mu}b, while the experimental upper-limit cross section for the former reaction is about 21{sup -21}{sup +38} nb. The intensity of suitable radioactive beams is not high enough at present to detect inverse fission. For the {sup 124}Sn + {sup 100}Mo reaction, the observed upper limits are below the estimates of current models for these reactions, probably due to fusion hindrance.
123073592
Identification of Excited States in the Tz=+1/2 Nucleus 75Rb: The Quest for Experimental Signatures of Collective Neutron-proton Correlations
Excited states in the T-z-1/2 nucleus Rb-75 were observed for the first time using the Ca-40(Ca-40,alpha p) reaction at 128 MeV. Identification was achieved using events detected by the Daresbury recoil separator in coincidence with gamma rays detected in the 45 element EUROGAM I Ge-detector array. Threefold events were used to build a decay scheme which consists of two rotational bands observed to I-pi=(45+/2) and I-pi=(33-/2). The positive parity band in Rb-75 behaves similarly to a negative-parity band in Kr-74 and contains a region of alignment at (h) over bar omega approximate to 0.75 MeV. These data, and those of Sr-77, be interpreted by treating protons and neutrons separately in a cranked shell model approach despite a recent suggestion for the presence of T=1 neutron-proton pairing correlations in the neighboring self-conjugate, odd-odd Rb-74 ground state band. Our study suggests that some experimental observables such as the energy levels and moments of inertia, may not be able to differentiate between different T=1 pairing phases in these T-z=1/2 nuclei. (Less)
121428597
Measurement of g factors of excited states in radioactive beams by the transient field technique : 132Te
Abstract The g factor of the 2 1 + state in 132 52 Te, E ( 2 1 + ) = 0.9739 MeV , τ = 2.6 ps , was measured by the transient field technique applied to a radioactive beam. The development of an experimental approach necessary for work in radioactive beam environments is described. The result g = 0.28 ( 15 ) agrees with the previous measurement by the recoil-in-vacuum technique, but here the sign of the g factor is measured as well.