Scalable Compression of Deep Neural Networks

Deep neural networks generally involve some layers with mil- lions of parameters, making them difficult to be deployed and updated on devices with limited resources such as mobile phones and other smart embedded systems. In this paper, we propose a scalable representation of the network parameters, so that different applications can select the most suitable bit rate of the network based on their own storage constraints. Moreover, when a device needs to upgrade to a high-rate network, the existing low-rate network can be reused, and only some incremental data are needed to be downloaded. We first hierarchically quantize the weights of a pre-trained deep neural network to enforce weight sharing. Next, we adaptively select the bits assigned to each layer given the total bit budget. After that, we retrain the network to fine-tune the quantized centroids. Experimental results show that our method can achieve scalable compression with graceful degradation in the performance.Comment: 5 pages, 4 figures, ACM Multimedia 201

Discovering an Invisibly Decaying Higgs at Hadron Colliders

A Higgs boson lighter than 2 m_W that decays mostly into invisible channels (e.g., dark matter particles) is theoretically well-motivated. We study the prospects for discovery of such an invisible Higgs, h_inv, at the LHC and the Tevatron in three production modes: (1) in association with a Z, (2) through Weak Boson Fusion (WBF), and (3) accompanied by a jet. In the Z+h_inv channel, we show that the LHC can yield a discovery signal above 5 sigma with 10 fb-1 of integrated luminosity for a Higgs mass of 120 GeV. With 30 fb-1 the discovery reach extends up to a Higgs mass of 160 GeV. We also study the extraction of the h_inv mass from production cross sections at the LHC, and find that combining WBF and Z+h_inv allows a relatively model-independent determination of the h_inv mass with an uncertainty of 35-50 GeV (15-20 GeV) with 10 (100) fb-1. At the Tevatron, a 3 sigma observation of a 120 GeV h_inv in any single channel is not possible with less than 12 fb-1 per detector. However, we show that combining the signal from WBF with the previously-studied Z+h_inv channel allows a 3 sigma observation of h_inv with 7 fb-1 per detector. Because of overwhelming irreducible backgrounds, h_inv+j is not a useful search channel at either the Tevatron or the LHC, despite the larger production rate.Comment: 21 pages, 1 figure; v2: added refs, added discussion of invisible Higgs mass extraction from cross sections at LHC; v3: minor clarifications in text, version to appear in PR

Reduction of Activation Energy Barrier of Stone-Wales Transformation in Endohedral Metallofullerenes

We examine effects of encapsulated metal atoms inside a C$_{60}$ molecule on the activation energy barrier to the Stone-Wales transformation using {\it ab initio} calculations. The encapsulated metal atoms we study are K, Ca and La which nominally donate one, two and three electrons to the C$_{60}$ cage, respectively. We find that isomerization of the endohedral metallofullerene via the Stone-Wales transformation can occur more easily than that of the empty fullerene owing to the charge transfer. When K, Ca and La atoms are encapsulated inside the fullerene, the activation energy barriers are lowered by 0.30, 0.55 and 0.80 eV, respectively compared with that of the empty C$_{60}$ (7.16 eV). The lower activation energy barrier of the Stone-Wales transformation implies the higher probability of isomerization and coalescence of metallofullerenes, which require a series of Stone-Wales transformations.Comment: 13 pages, 3 figures, 1 tabl