The geometry, electronic, and structural properties of an unusually stable boron cage made of 80 boron atoms are studied, using ab initio calculations. The shape of this cluster is very similar to that of the well-known ${\mathrm{C}}_{60}$ fullerene, but in the ${\mathrm{B}}_{80}$ case, there is an additional atom in the center of each hexagon. The resulting cage preserves the $I_h$ symmetry, has a relatively large highest occupied and lowest unoccupied energy gap ($\sim 1\mathrm{eV}$) and, most importantly, is energetically more stable than boron double rings, which were detected in experiments and considered as building blocks of boron nanotubes. To our knowledge, this is the most stable boron cage studied so far.

We construct the three-loop four-point amplitude of $\mathcal{N}=8$ supergravity using the unitarity method. The amplitude is ultraviolet finite in four dimensions. Novel cancellations, not predicted by traditional superspace power-counting arguments, render its degree of divergence in $D$ dimensions no worse than that of $\mathcal{N}=4$ super-Yang-Mills theory—a finite theory in four dimensions. Similar cancellations can be identified at all loop orders in certain unitarity cuts, suggesting that $\mathcal{N}=8$ supergravity may be a perturbatively finite theory of quantum gravity.

We report the first observation of the associated production of a $W$ boson and a $Z$ boson. This result is based on $1.1{\mathrm{fb}}^{-1}$ of integrated luminosity from $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ collected with the CDF II detector at the Fermilab Tevatron. We observe 16 $WZ$ candidates passing our event selection with an expected background of $2.7\pm 0.4$ events. A fit to the missing transverse energy distribution indicates an excess of events compared to the background expectation corresponding to a significance equivalent to 6 standard deviations. The measured cross section is $\sigma (p\overline{p}\to WZ)={5.0}_{-1.6}^{+1.8}\mathrm{pb}$, consistent with the standard model expectation.

We consider the problem of discriminating two different quantum states in the setting of asymptotically many copies, and determine the minimal probability of error. This leads to the identification of the quantum Chernoff bound, thereby solving a long-standing open problem. The bound reduces to the classical Chernoff bound when the quantum states under consideration commute. The quantum Chernoff bound is the natural symmetric distance measure between quantum states because of its clear operational meaning and because it does not seem to share some of the undesirable features of other distance measures.

We report on a stable optical trap suitable for a macroscopic mirror, wherein the dynamics of the mirror are fully dominated by radiation pressure. The technique employs two frequency-offset laser fields to simultaneously create a stiff optical restoring force and a viscous optical damping force. We show how these forces may be used to optically trap a free mass without introducing thermal noise, and we demonstrate the technique experimentally with a 1 g mirror. The observed optical spring has an inferred Young’s modulus of 1.2 TPa, 20% stiffer than diamond. The trap is intrinsically cold and reaches an effective temperature of 0.8 K, limited by technical noise in our apparatus.

The interaction between elasticity and capillarity is used to produce three-dimensional structures through the wrapping of a liquid droplet by a planar sheet. The final encapsulated 3D shape is controlled by tailoring the initial geometry of the flat membrane. Balancing interfacial energy with elastic bending energy provides a critical length scale below which encapsulation cannot occur, which is verified experimentally. This length is found to depend on the thickness as $h^{3/2}$, a scaling favorable to miniaturization which suggests a new way of mass production of 3D micro- or nanoscale objects.

We report on the first demonstration of a quaternary-logical resonatorless optical memory element with information encoded in the structural phase of a single 80 nm gallium nanoparticle. The size of the memory element is comparable with bits in next-generation hard disks, and radically smaller than previously suggested memories exploiting optical resonators. Furthermore, the energy required for switching the nanoparticle is an order of magnitude less than needed in DVD, DVR, or hard disk technologies.

The energy splitting of the ${}^{229}\mathrm{Th}$ ground-state doublet is measured to be $7.6\pm 0.5\mathrm{eV}$, significantly greater than earlier measurements. Gamma rays produced following the alpha decay of ${}^{233}\mathrm{U}$ ($105\mu \mathrm{Ci}$) were counted in the NASA/electron beam ion trap x-ray microcalorimeter spectrometer with an experimental energy resolution of 26 eV (FWHM). A difference technique was applied to the gamma-ray decay of the 71.82 keV level that populates both members of the doublet. A positive correction amounting to 0.6 eV was made for the unobserved interband decay of the 29.19 keV state ($29.19\to 0\mathrm{keV}$).

The security of quantum key distribution is typically defined in terms of the mutual information between the distributed key $S$ and the outcome of an optimal measurement applied to the adversary’s system. We show that even if this so-called accessible information is small, the key $S$ might not be secure enough to be used in applications such as one-time pad encryption. This flaw is due to a locking property of the accessible information: one additional (physical) bit of information can increase the accessible information by more than one bit.

High magnetic fields were used to deform spherical nanocapsules, self-assembled from bolaamphiphilic sexithiophene molecules. At low fields the deformation—measured through linear birefringence—scales quadratically with the capsule radius and with the magnetic field strength. These data confirm a long standing theoretical prediction [W. Helfrich, Phys. Lett. A 43, 409 (1973)], and permit the determination of the bending rigidity of the capsules as $(2.6\pm 0.8)\times {10}^{-21}\mathrm{J}$. At high fields, an enhanced rigidity is found which cannot be explained within the Helfrich model. We propose a complete form of the free energy functional that accounts for this behavior, and allows discussion of the formation and stability of nanocapsules in solution.

An excess of ${}^{60}\mathrm{Fe}$ in 2.4–$3.2\times {10}^6$ year old ferromanganese crust (237KD) from the deep Pacific Ocean has been considered as evidence for the delivery of debris from a nearby supernova explosion to Earth. Extremely high ${}^3\mathrm{He}/{}^4\mathrm{He}$ (up to $6.12\times {10}^{-3}$) and ${}^3\mathrm{He}$ concentrations (up to $8\times {10}^9\mathrm{\text{atoms}}/\mathrm{g}$) measured in 237KD cannot be supernova-derived. The helium is produced by galactic cosmic rays (GCR) and delivered in micrometeorites that have survived atmospheric entry to be trapped by the crust. ${}^{60}\mathrm{Fe}$ is produced by GCR reactions on Ni in extraterrestrial material. The maximum ${}^3\mathrm{He}/{}^{60}\mathrm{Fe}$ of 237KD (80–850) is comparable to the GCR ${}^3\mathrm{He}/{}^{60}\mathrm{Fe}$ production ratio (400–500) predicted for Ni-bearing minerals in iron meteorites. The excess ${}^{60}\mathrm{Fe}$ can be plausibly explained by the presence of micrometeorites trapped by the crust, rather than injection from a supernova source.

We present an analysis which shows that the ranges of space and time scales spanned by a system are not invariant under Lorentz transformation. This implies the existence of a frame of reference which minimizes an aggregate measure of the range of space and time scales. Such a frame is derived, for example, for the following cases: free electron laser, laser-plasma accelerator, and particle beams interacting with electron clouds. The implications for experimental, theoretical, and numerical studies are discussed. The most immediate relevance is the reduction by orders of magnitude in computer simulation run times for such systems.

Optical pumping by blackbody radiation is a feature shared by all polar molecules and fundamentally limits the time that these molecules can be kept in a single quantum state in a trap. To demonstrate and quantify this, we have monitored the optical pumping of electrostatically trapped OH and OD radicals by room-temperature blackbody radiation. Transfer of these molecules to rotationally excited states by blackbody radiation at 295 K limits the $1/e$ trapping time for OH and OD in the $X^2{\Pi }_{3/2}$, $v^{\prime \prime }=0$, $J^{\prime \prime }=3/2(f)$ state to 2.8 and 7.1 s, respectively.

Arrays of coupled heat engines are proposed as a paradigmatic model to study the trade-off between individual and collective behavior in linear irreversible thermodynamics. The analysis reveals the existence of a control parameter which selects different operation regimes of the whole array. In particular, the regimes of maximum efficiency and maximum power are considered, giving for the latter a general derivation of the Curzon-Ahlborn efficiency which surprisingly does not depend on whether or not the individual engines in the array work at maximum power.

Whether or not the upcoming cycle 24 of solar activity will be strong is being hotly debated. The solar cycle is produced by a complex dynamo mechanism. We model the last few solar cycles by “feeding” observational data of the Sun’s polar magnetic field into our solar dynamo model. Our results fit the observed sunspot numbers of cycles 21–23 reasonably well and predict that cycle 24 will be about 35% weaker than cycle 23.

We measure the spatial distribution of the local density of states (LDOS) at cleaved surfaces of $\mathrm{InAs}/\mathrm{GaSb}$ isolated quantum wells and double quantum wells (DQWs) by low-temperature scanning tunneling spectroscopy. Distinct standing wave patterns of LDOS corresponding to subbands are observed. These LDOS patterns and subband energies agree remarkably well with simple calculations with tip-induced band bending. Furthermore, for the DQWs, coupling of electronic states between the quantum wells is also clearly observed.

The quantum dynamics of colliding Bose-Einstein condensates with 150 000 atoms are simulated directly from the Hamiltonian using the stochastic positive-$P$ method. Two-body correlations between the scattered atoms and their velocity distribution are found for experimentally accessible parameters. Hanbury Brown–Twiss or thermal-like correlations are seen for copropagating atoms, while number correlations for counterpropagating atoms are even stronger than thermal correlations at short times. The coherent phase grains grow in size as the collision progresses with the onset of growth coinciding with the beginning of stimulated scattering. The method is versatile and usable for a range of cold atom systems.

It is commonly assumed that high-energy $\gamma$ rays are made via either purely electromagnetic processes or the hadronic process of pion production, followed by decay. We investigate astrophysical contexts where a third process ($A^{*}$) would dominate: namely, the photodisintegration of highly boosted nuclei followed by daughter deexcitation. Starburst regions such as Cygnus OB2 appear to be promising sites for TeV $\gamma$-ray emission via this mechanism. A unique feature of the $A^{*}$ process is a sharp flattening of the energy spectrum below $\sim 10\mathrm{TeV}/(T/\mathrm{eV})$ for $\gamma$-ray emission from a thermal region of temperature $T$. The $A^{*}$ mechanism described herein offers an important contribution to $\gamma$-ray astronomy in the era of intense observational activity.

In a granular gas of rough particles the axis of rotation is shown to be correlated with the translational velocity of the particles. The average relative orientation of angular and linear velocities depends on the parameters which characterize the dissipative nature of the collision. We derive a simple theory for these correlations and validate it with numerical simulations for a wide range of coefficients of normal and tangential restitution. The limit of smooth spheres is shown to be singular: even an arbitrarily small roughness of the particles gives rise to orientational correlations.

We factor the number 157573 using an NMR implementation of Gauss sums. Although the current implementation is classical and scales exponentially, we believe that an extension to the quantum regime using entangled states is possible.