Search

Immersive Virtual Reality typically requires a head-mounted display (HMD) to visualize the environment and hand-held controllers to interact with the virtual objects. Recently, many applications display full-body avatars to represent the user and animate the arms to follow the controllers. Embodiment is higher when the self-avatar movements align correctly with the user. However, having a full-body self-avatar following the user's movements can be challenging due to the disparities between the virtual body and the user's body. This can lead to misalignments in the hand position that can be noticeable when interacting with virtual objects. In this work, we propose five different interaction modes to allow the user to interact with virtual objects despite the self-avatar and controller misalignment and study their influence on embodiment, proprioception, preference, and task performance. We modify aspects such as whether the virtual controllers are rendered, whether controllers are rendered in their real physical location or attached to the user's hand, and whether stretching the avatar arms to always reach the real controllers. We evaluate the interaction modes both quantitatively (performance metrics) and qualitatively (embodiment, proprioception, and user preference questionnaires). Our results show that the stretching arms solution, which provides body continuity and guarantees that the virtual hands or controllers are in the correct location, offers the best results in embodiment, user preference, proprioception, and performance. Also, rendering the controller does not have an effect on either embodiment or user preference., Comment: Presented in CHI'24

An increasing number of virtual reality applications require environments that emulate real-world conditions. These environments often involve dynamic virtual humans showing realistic behaviors. Understanding user perception and navigation among these virtual agents is key for designing realistic and effective environments featuring groups of virtual humans. While collision risk significantly influences human locomotion in the real world, this risk is largely absent in virtual settings. This paper studies the impact of the expected collision feedback on user perception and interaction with virtual crowds. We examine the effectiveness of commonly used collision feedback techniques (auditory cues and tactile vibrations) as well as inducing participants to expect that a physical bump with a real person might occur, as if some virtual humans actually correspond to real persons embodied into them and sharing the same physical space. Our results indicate that the expected collision feedback significantly influences both participant behavior (encompassing global navigation and local movements) and subjective perceptions of presence and copresence. Specifically, the introduction of a perceived risk of actual collision was found to significantly impact global navigation strategies and increase the sense of presence. Auditory cues had a similar effect on global navigation and additionally enhanced the sense of copresence. In contrast, vibrotactile feedback was primarily effective in influencing local movements., Comment: Presented in IEEE VR 2024

High-quality motion reconstruction that follows the user's movements can be achieved by high-end mocap systems with many sensors. However, obtaining such animation quality with fewer input devices is gaining popularity as it brings mocap closer to the general public. The main challenges include the loss of end-effector accuracy in learning-based approaches, or the lack of naturalness and smoothness in IK-based solutions. In addition, such systems are often finely tuned to a specific number of trackers and are highly sensitive to missing data e.g., in scenarios where a sensor is occluded or malfunctions. In response to these challenges, we introduce DragPoser, a novel deep-learning-based motion reconstruction system that accurately represents hard and dynamic on-the-fly constraints, attaining real-time high end-effectors position accuracy. This is achieved through a pose optimization process within a structured latent space. Our system requires only one-time training on a large human motion dataset, and then constraints can be dynamically defined as losses, while the pose is iteratively refined by computing the gradients of these losses within the latent space. To further enhance our approach, we incorporate a Temporal Predictor network, which employs a Transformer architecture to directly encode temporality within the latent space. This network ensures the pose optimization is confined to the manifold of valid poses and also leverages past pose data to predict temporally coherent poses. Results demonstrate that DragPoser surpasses both IK-based and the latest data-driven methods in achieving precise end-effector positioning, while it produces natural poses and temporally coherent motion. In addition, our system showcases robustness against on-the-fly constraint modifications, and exhibits exceptional adaptability to various input configurations and changes.

Accurate and reliable human motion reconstruction is crucial for creating natural interactions of full-body avatars in Virtual Reality (VR) and entertainment applications. As the Metaverse and social applications gain popularity, users are seeking cost-effective solutions to create full-body animations that are comparable in quality to those produced by commercial motion capture systems. In order to provide affordable solutions, though, it is important to minimize the number of sensors attached to the subject's body. Unfortunately, reconstructing the full-body pose from sparse data is a heavily under-determined problem. Some studies that use IMU sensors face challenges in reconstructing the pose due to positional drift and ambiguity of the poses. In recent years, some mainstream VR systems have released 6-degree-of-freedom (6-DoF) tracking devices providing positional and rotational information. Nevertheless, most solutions for reconstructing full-body poses rely on traditional inverse kinematics (IK) solutions, which often produce non-continuous and unnatural poses. In this article, we introduce SparsePoser, a novel deep learning-based solution for reconstructing a full-body pose from a reduced set of six tracking devices. Our system incorporates a convolutional-based autoencoder that synthesizes high-quality continuous human poses by learning the human motion manifold from motion capture data. Then, we employ a learned IK component, made of multiple lightweight feed-forward neural networks, to adjust the hands and feet toward the corresponding trackers. We extensively evaluate our method on publicly available motion capture datasets and with real-time live demos. We show that our method outperforms state-of-the-art techniques using IMU sensors or 6-DoF tracking devices, and can be used for users with different body dimensions and proportions., Comment: Published in ACM TOG https://dl.acm.org/doi/10.1145/3625264 and presented in SIGGRAPH ASIA 2023

Real-time animation of virtual characters has traditionally been accomplished by playing short sequences of animations structured in the form of a graph. These methods are time-consuming to set up and scale poorly with the number of motions required in modern virtual environments. The ever-increasing need for highly-realistic virtual characters in fields such as entertainment, virtual reality, or the metaverse has led to significant advances in the field of data-driven character animation. Techniques like Motion Matching have provided enough versatility to conveniently animate virtual characters using a selection of features from an animation database. Data-driven methods retain the quality of the captured animations, thus delivering smoother and more natural-looking animations. In this work, we researched and developed a Motion Matching technique for the Unity game engine. In this thesis, we present our findings on how to implement an animation system based on Motion Matching. We also introduce a novel method combining body orientation prediction with Motion Matching to animate avatars for consumer-grade virtual reality systems., Comment: Master Thesis. GitHub Project: https://github.com/JLPM22/MotionMatching

In the era of the metaverse, self-avatars are gaining popularity, as they can enhance presence and provide embodiment when a user is immersed in Virtual Reality. They are also very important in collaborative Virtual Reality to improve communication through gestures. Whether we are using a complex motion capture solution or a few trackers with inverse kinematics (IK), it is essential to have a good match in size between the avatar and the user, as otherwise mismatches in self-avatar posture could be noticeable for the user. To achieve such a correct match in dimensions, a manual process is often required, with the need for a second person to take measurements of body limbs and introduce them into the system. This process can be time-consuming, and prone to errors. In this paper, we propose an automatic measuring method that simply requires the user to do a small set of exercises while wearing a Head-Mounted Display (HMD), two hand controllers, and three trackers. Our work provides an affordable and quick method to automatically extract user measurements and adjust the virtual humanoid skeleton to the exact dimensions. Our results show that our method can reduce the misalignment produced by the IK system when compared to other solutions that simply apply a uniform scaling to an avatar based on the height of the HMD, and make assumptions about the locations of joints with respect to the trackers., Comment: Published in Virtual Reality Springer

The use of self-avatars is gaining popularity thanks to affordable VR headsets. Unfortunately, mainstream VR devices often use a small number of trackers and provide low-accuracy animations. Previous studies have shown that the Sense of Embodiment, and in particular the Sense of Agency, depends on the extent to which the avatar's movements mimic the user's movements. However, few works study such effect for tasks requiring a precise interaction with the environment, i.e., tasks that require accurate manipulation, precise foot stepping, or correct body poses. In these cases, users are likely to notice inconsistencies between their self-avatars and their actual pose. In this paper, we study the impact of the animation fidelity of the user avatar on a variety of tasks that focus on arm movement, leg movement and body posture. We compare three different animation techniques: two of them using Inverse Kinematics to reconstruct the pose from sparse input (6 trackers), and a third one using a professional motion capture system with 17 inertial sensors. We evaluate these animation techniques both quantitatively (completion time, unintentional collisions, pose accuracy) and qualitatively (Sense of Embodiment). Our results show that the animation quality affects the Sense of Embodiment. Inertial-based MoCap performs significantly better in mimicking body poses. Surprisingly, IK-based solutions using fewer sensors outperformed MoCap in tasks requiring accurate positioning, which we attribute to the higher latency and the positional drift that causes errors at the end-effectors, which are more noticeable in contact areas such as the feet., Comment: Accepted in IEEE VR 2023

For an autonomous vehicle, the ability to sense its surroundings and to build an overall representation of the environment by fusing different sensor data streams is fundamental. To this end, the poses of all sensors need to be accurately determined. Traditional calibration methods are based on: 1) using targets specifically designed for calibration purposes in controlled environments, 2) optimizing a quality metric of the point clouds collected while traversing an unknown but static environment, or 3) optimizing the match among per-sensor incremental motion observations along a motion path fulfilling special requirements. In real scenarios, however, the online applicability of these methods can be limited, as they are typically highly dynamic, contain degenerate paths, and require fast computations. In this paper, we propose an approach that tackles some of these challenges by formulating the calibration problem as a joint but structured optimization problem of all sensor calibrations that takes as input a summary of the point cloud information consisting of ground points and pole detections. We demonstrate the efficiency and quality of the results of the proposed approach in a set of experiments with LiDAR simulation and real data from an urban trip., Comment: 8 pages, 12 figures, The 2022 IEEE/RSJ International Conference on Intelligent Robots and Systems

The use of self-avatars in a VR application can enhance presence and embodiment which leads to a better user experience. In collaborative VR it also facilitates non-verbal communication. Currently it is possible to track a few body parts with cheap trackers and then apply IK methods to animate a character. However, the correspondence between trackers and avatar joints is typically fixed ad-hoc, which is enough to animate the avatar, but causes noticeable mismatches between the user's body pose and the avatar. In this paper we present a fast and easy to set up system to compute exact offset values, unique for each user, which leads to improvements in avatar movement. Our user study shows that the Sense of Embodiment increased significantly when using exact offsets as opposed to fixed ones. We also allowed the users to see a semitransparent avatar overlaid with their real body to objectively evaluate the quality of the avatar movement with our technique., Comment: GitHub: https://github.com/UPC-ViRVIG/AvatarGo

The animation of user avatars plays a crucial role in conveying their pose, gestures, and relative distances to virtual objects or other users. Self-avatar animation in immersive VR helps improve the user experience and provides a Sense of Embodiment. However, consumer-grade VR devices typically include at most three trackers, one at the Head Mounted Display (HMD), and two at the handheld VR controllers. Since the problem of reconstruction the user pose from such sparse data is ill-defined, especially for the lower body, the approach adopted by most VR games consists of assuming the body orientation matches that of the HMD, and applying animation blending and time-warping from a reduced set of animations. Unfortunately, this approach produces noticeable mismatches between user and avatar movements. In this work we present a new approach to animate user avatars that is suitable for current mainstream VR devices. First, we use a neural network to estimate the user's body orientation based on the tracking information from the HMD and the hand controllers. Then we use this orientation together with the velocity and rotation of the HMD to build a feature vector that feeds a Motion Matching algorithm. We built a MoCap database with animations of VR users wearing a HMD and used it to test our approach on both self-avatars and other users' avatars. Our results show that our system can provide a large variety of lower body animations while correctly matching the user orientation, which in turn allows us to represent not only forward movements but also stepping in any direction., Comment: Project Website: https://github.com/UPC-ViRVIG/MMVR

Given a rational number $r$ such that $2r$ is not an integer, we prove that $\tan^2(r\pi)$ is irrational unless it is equal to $0$, $1$, $3$ or $\frac{1}{3}$, using only basic trigonometry and the Rational Root Theorem. Moreover, we deduce that $\tan(r\pi)$, $\cos^2(r\pi)$ ans $\cos(r\pi)$ are irrational numbers except in usual cases., Comment: 2 pages

This paper investigates the problem of efficient computation of physically consistent multi-contact behaviors. Recent work showed that under mild assumptions, the problem could be decomposed into simpler kinematic and centroidal dynamic optimization problems. Based on this approach, we propose a general convex relaxation of the centroidal dynamics leading to two computationally efficient algorithms based on iterative resolutions of second order cone programs. They optimize centroidal trajectories, contact forces and, importantly, the timing of the motions. We include the approach in a kino-dynamic optimization method to generate full-body movements. Finally, the approach is embedded in a mixed-integer solver to further find dynamically consistent contact sequences. Extensive numerical experiments demonstrate the computational efficiency of the approach, suggesting that it could be used in a fast receding horizon control loop. Executions of the planned motions on simulated humanoids and quadrupeds and on a real quadruped robot further show the quality of the optimized motions.

We study the production of $t{\bar t}h$ and $t{\bar t}hh$ at hadron colliders, in the minimal Composite Higgs Models, based on the coset $SO(5)/SO(4)$. We explore the fermionic representations ${\bf 5}$ and ${\bf 14}$. A detailed phenomenological analysis is performed, covering the energy range of the LHC and its High Luminosity upgrade, as well as that of a future 100 TeV hadron collider. Both resonant and non-resonant production are considered, stressing the interplay and complementary interest of these channels with each other and double Higgs production. We provide sets of representative points with detailed experimental outcomes in terms of modification of the cross sections as well as resonance masses and branching ratios. For non-resonant production, we gauge the relative importance of Yukawa, Higgs trilinear, and contact $t\bar{t}hh$ vertices to these processes, and consider the prospect for distinguishing the fermion representations from each other and from the Standard Model. In the production of top partners, we find that the three-body decay channel $W^+ W^- t$ becomes significant in certain regions of parameter space having a degenerate spectrum, and is further enhanced with energy. This motivates both higher energy machines as well as the need to go beyond the current analysis performed for the searches for these resonances., Comment: 68 pages, 21 figures, supplementary figures in ancillary directory

By using purely algebraic tools, we establish well-known properties of roots of Chebyshev polynomials. Especially, we show that these zeros are simple and lie in $(-1,1)$ and we prove in two ways that they are mostly irrational., Comment: 6 pages

In the simple Higgs-portal dark matter model with a conserved dark matter number, we show that there exists a non-topological soliton state of dark matter. This state has smaller energy per dark matter number than a free particle state and has its interior in the electroweak symmetric vacuum. It could be produced in the early universe from first-order electroweak phase transition and contribute most of dark matter. This electroweak symmetric dark matter ball is a novel macroscopic dark matter candidate with an energy density of the electroweak scale and a mass of 1 gram or above. Because of its electroweak-symmetric interior, the dark matter ball has a large geometric scattering cross section off a nucleon or a nucleus. Dark matter and neutrino experiments with a large-size detector like Xenon1T, BOREXINO and JUNO have great potential to discover electroweak symmetric dark matter balls. We also discuss the formation of bound states of a dark matter ball and ordinary matter., Comment: 50 pages, 10 figures

The discovery of the Higgs boson in 2012, by the ATLAS and CMS experiments, was a success achieved with only a percent of the entire dataset foreseen for the LHC. It opened a landscape of possibilities in the study of Higgs boson properties, Electroweak Symmetry breaking and the Standard Model in general, as well as new avenues in probing new physics beyond the Standard Model. Six years after the discovery, with a conspicuously larger dataset collected during LHC Run 2 at a 13 TeV centre-of-mass energy, the theory and experimental particle physics communities have started a meticulous exploration of the potential for precision measurements of its properties. This includes studies of Higgs boson production and decays processes, the search for rare decays and production modes, high energy observables, and searches for an extended electroweak symmetry breaking sector. This report summarises the potential reach and opportunities in Higgs physics during the High Luminosity phase of the LHC, with an expected dataset of pp collisions at 14 TeV, corresponding to an integrated luminosity of 3 ab$^{-1}$. These studies are performed in light of the most recent analyses from LHC collaborations and the latest theoretical developments. The potential of an LHC upgrade, colliding protons at a centre-of-mass energy of 27 TeV and producing a dataset corresponding to an integrated luminosity of 15 ab$^{-1}$, is also discussed., Comment: Report from Working Group 2 on the Physics of the HL-LHC, and Perspectives at the HE-LHC, 364 pages

Humanoid robots dynamically navigate an environment by interacting with it via contact wrenches exerted at intermittent contact poses. Therefore, it is important to consider dynamics when planning a contact sequence. Traditional contact planning approaches assume a quasi-static balance criterion to reduce the computational challenges of selecting a contact sequence over a rough terrain. This however limits the applicability of the approach when dynamic motions are required, such as when walking down a steep slope or crossing a wide gap. Recent methods overcome this limitation with the help of efficient mixed integer convex programming solvers capable of synthesizing dynamic contact sequences. Nevertheless, its exponential-time complexity limits its applicability to short time horizon contact sequences within small environments. In this paper, we go beyond current approaches by learning a prediction of the dynamic evolution of the robot centroidal momenta, which can then be used for quickly generating dynamically robust contact sequences for robots with arms and legs using a search-based contact planner. We demonstrate the efficiency and quality of the results of the proposed approach in a set of dynamically challenging scenarios.

Recently, the centroidal momentum dynamics has received substantial attention to plan dynamically consistent motions for robots with arms and legs in multi-contact scenarios. However, it is also non convex which renders any optimization approach difficult and timing is usually kept fixed in most trajectory optimization techniques to not introduce additional non convexities to the problem. But this can limit the versatility of the algorithms. In our previous work, we proposed a convex relaxation of the problem that allowed to efficiently compute momentum trajectories and contact forces. However, our approach could not minimize a desired angular momentum objective which seriously limited its applicability. Noticing that the non-convexity introduced by the time variables is of similar nature as the centroidal dynamics one, we propose two convex relaxations to the problem based on trust regions and soft constraints. The resulting approaches can compute time-optimized dynamically consistent trajectories sufficiently fast to make the approach realtime capable. The performance of the algorithm is demonstrated in several multi-contact scenarios for a humanoid robot. In particular, we show that the proposed convex relaxation of the original problem finds solutions that are consistent with the original non-convex problem and illustrate how timing optimization allows to find motion plans that would be difficult to plan with fixed timing., Comment: 7 pages, 4 figures, ICRA 2018

By using the Calkin-Wilf tree, we prove the irrationality of numbers of the form $\alpha=\frac{\sqrt{N}+p}{q}$ where $N$ is a positive integer which is not a perfect square, $p$ is a rational integer such that $p^2

We are interested in irrationality of roots for seven important families of polynomials : Tchebichef polynomials, Legendre polynomials, Laguerre polynomials, Hermite polynomials, Bessel polynomials, Bernoulli polynomials and Euler polynomials. One first proves, for the most part of them, existence of real roots then one studies the irrationality of them. The methods used are based on elementary arithmetical properties of algebraic numbers, some of them becoming from more general proofs that have allowed to derive the irreducibility of some of these polynomials., Comment: 39 pages, in French

On propose une m\'ethode de r\'esolution effective de l'\'equation diophantienne $(E_2): ax^2-by^2=1$ o\`u $a$ et $b$ sont des entiers naturels non nuls et premiers entre eux. Cette m\'ethode s'appuie sur le d\'eveloppement en fraction continu\'ee de certains nombres irrationnels quadratiques que l'on d\'ecrit compl\`etement. On commence par utiliser ces d\'eveloppements pour r\'esoudre certaines \'equations de Pell-Fermat g\'en\'eralis\'ees avant d'appliquer \`a l'\'equation $(E_2)$ les r\'esultats obtenus., Comment: 18 pages, in French

We give two trees allowing to represent all positive rational numbers. These trees can be seen as ternary and quinary analogues of the Calkin-Wilf tree. For each of these two trees, we give recurrence formulas allowing to compute the rational number corresponding to the node n. These are analogues of the formulas given by Donald Knuth and Moshe Newman for the Calkin-Wilf tree. Finally, we show that the two sequences we have obtained, together with Calkin-Wilf sequence, are the only ones which satisfy a relation analogue to Newman's relation and enumerate the positive rationals.

The radial excitation of the global symmetry-breaking vacuum in composite Higgs models, called the "global Higgs", has been recently a focus of investigation. In this paper we study the prospects for detecting this composite scalar at the 13 TeV LHC. We compute the global Higgs production rates and estimate the discovery potential of a global Higgs decaying into top quark pairs and into Higgs and electroweak gauge bosons with subsequent hadronic decays. The global Higgs may also decay into fermion resonances such as top partners, providing a new window into compositeness. We show that top partner jets can be effectively unresolved in some regions of the parameter space. Such "boosted top partner" signatures would deserve the development of dedicated substructure analyses., Comment: 27 pages, 7 figures. v2: Comments added. Matches JHEP version

Linear models for control and motion generation of humanoid robots have received significant attention in the past years, not only due to their well known theoretical guarantees, but also because of practical computational advantages. However, to tackle more challenging tasks and scenarios such as locomotion on uneven terrain, a more expressive model is required. In this paper, we are interested in contact interaction-centered motion optimization based on the momentum dynamics model. This model is non-linear and non-convex; however, we find a relaxation of the problem that allows us to formulate it as a single convex quadratically-constrained quadratic program (QCQP) that can be very efficiently optimized. Furthermore, experimental results suggest that this relaxation is tight and therefore useful for multi-contact planning. This convex model is then coupled to the optimization of end-effector contacts location using a mixed integer program, which can be solved in realtime. This becomes relevant e.g. to recover from external pushes, where a predefined stepping plan is likely to fail and an online adaptation of the contact location is needed. The performance of our algorithm is demonstrated in several multi-contact scenarios for humanoid robot., Comment: 8 pages

We consider scenarios of Higgs compositeness where the Higgs doublet arises as a pseudo-Nambu Goldstone boson. Our focus is the physical scalar ("radial") excitation associated with the global symmetry breaking vacuum, which we call the "global Higgs". For the minimal case of a $SO(5)/SO(4)$ coset, the couplings of the global Higgs to Standard Model (SM) particles are fully determined by group theoretical factors and two decay constants. The global Higgs also couples to the composite resonances of the theory, inducing an interaction with the SM gauge bosons at one-loop. We thoroughly analyze representative fermionic sectors, considering a global Higgs both in the $\bf 5$ and $\bf 14$ representations of $SO(5)$ and taking into account the renormalization group evolution of couplings in the composite sector. We derive the one-loop effective couplings and all decays of the global Higgs, showing that its decay width over mass can range from $ O (10^{-3})$ to $ O(1)$. Because of the multiplicity of the resonances, the coupling of the global Higgs to gluons is sizeable, potentially opening a new window into composite models at the LHC., Comment: 27 pages, 2 figures. v3: References and comments added. Matches JHEP version

Stochastic Optimal Control (SOC) typically considers noise only in the process model, i.e. unknown disturbances. However, in many robotic applications involving interaction with the environment, such as locomotion and manipulation, uncertainty also comes from lack of precise knowledge of the world, which is not an actual disturbance. We analyze the effects of also considering noise in the measurement model, by developing a SOC algorithm based on risk-sensitive control, that includes the dynamics of an observer in such a way that the control law explicitly depends on the current measurement uncertainty. In simulation results on a simple 2D manipulator, we have observed that measurement uncertainty leads to low impedance behaviors, a result in contrast with the effects of process noise that creates stiff behaviors. This suggests that taking into account measurement uncertainty could be a potentially very interesting way to approach problems involving uncertain contact interactions., Comment: 17 pages, 5 figures - this version is the one published at WAFR 2016 to fulfill the open access requirements of the EU commission, please refer to the previous version for the complete derivation of the algorithm

We present a simple microscopic realization of a pseudo-Nambu-Goldstone (pNGB) boson Higgs scenario arising from the breaking of $SO(5) \rightarrow SO(4)$. The Higgs constituents are explicitly identified as well as the interactions responsible for forming the bound state and breaking the electroweak symmetry. This outcome follows from the presence of four-fermion interactions with a super-critical coupling, and uses the Nambu-Jona-Lasinio mechanism to break the global $SO(5)$ symmetry. The Higgs potential is found to be insensitive to high energy scales due to the existence of an approximate infrared fixed point. The appearance of vector resonances is described and the correspondence with other proposals in the literature established. The model described here is significantly simpler than other recent ultraviolet completions of pNGB scenarios. The observed Higgs mass can be accommodated, and agreement with electroweak precision tests achieved in certain regions of parameter space. There are also new vector-like fermions, some of which may lie within reach of the LHC. In addition, we predict a heavy standard model singlet scalar in the multi-TeV range. The amount of fine-tuning required in the model is studied. Finally, we show that such a scheme can be completed in the ultraviolet by a renormalizable theory., Comment: 32 pages plus appendices, 7 figures - reference added

We study a supersymmetric scenario with a quasi exact R-symmetry in light of the discovery of a Higgs resonance with a mass of 125 GeV. In such a framework, the additional adjoint superfields, needed to give Dirac masses to the gauginos, contribute both to the Higgs mass and to electroweak precision observables. We analyze the interplay between the two aspects, finding regions in parameter space in which the contributions to the precision observables are under control and a 125 GeV Higgs boson can be accommodated. We estimate the fine-tuning of the model finding regions of the parameter space still unexplored by the LHC with a fine-tuning considerably improved with respect to the minimal supersymmetric scenario. In particular, sizable non-holomorphic (non-supersoft) adjoints masses are required to reduce the fine-tuning., Comment: 20 pages, 5 figures. Fine-tuning discussion and computation improved, typos fixed, references added

We consider composite Higgs models where the Higgs is a pseudo-Nambu Goldstone boson arising from the spontaneous breaking of an approximate global symmetry by some underlying strong dynamics. We focus on the SO(5) -> SO(4) symmetry breaking pattern, assuming the partial compositeness paradigm. We study the consequences on Higgs physics of the fermionic representations produced by the strong dynamics, that mix with the Standard Model (SM) degrees of freedom. We consider models based on the lowest-dimensional representations of SO(5) that allow for the custodial protection of the Z -> b b coupling, i.e. the 5, 10 and 14. We find a generic suppression of the gluon fusion process, while the Higgs branching fractions can be enhanced or suppressed compared to the SM. Interestingly, a precise measurement of the Higgs boson couplings can distinguish between different realizations in the fermionic sector, thus providing crucial information about the nature of the UV dynamics., Comment: 55 pages, 18 figures, References added

In the first part of this article, we explore the background of computer-assisted learning from its beginnings in the early XIXth century and the first teaching machines, founded on theories of learning, at the start of the XXth century. With the arrival of the computer, it became possible to offer language learners different types of language activities such as comprehension tasks, simulations, etc. However, these have limits that cannot be overcome without some contribution from the field of natural language processing (NLP). In what follows, we examine the challenges faced and the issues raised by integrating NLP into CALL. We hope to demonstrate that the key to success in integrating NLP into CALL is to be found in multidisciplinary work between computer experts, linguists, language teachers, didacticians and NLP specialists.

We show that weak scale vector-like fermions with order one couplings to the Higgs can lead to a novel mechanism for a strongly first-order electroweak phase transition (EWPhT), through their tendency to drive the Higgs quartic coupling negative. These same fermions could also enhance the loop-induced branching fraction of the Higgs into two photons, as suggested by the recent discovery of a ~125 GeV Higgs-like state at the CERN Large Hadron Collider (LHC). Our results suggest that measurements of the diphoton decay rate of the Higgs and its self coupling, at the LHC or perhaps at a future lepton collider, could probe the EWPhT in the early Universe, with significant implications for the viability of electroweak baryogenesis scenarios., Comment: 6 pages, 1 figure. Revised version shows that the original conclusions hold in a distinct region of parameter space. New discussion on collider probes added

We perform a detailed study of a variety of LHC signals in supersymmetric models where lepton number is promoted to an (approximate) U(1)_R symmetry. Such a symmetry has interesting implications for naturalness, as well as flavor- and CP-violation, among others. Interestingly, it makes large sneutrino vacuum expectation values phenomenologically viable, so that a slepton doublet can play the role of the down-type Higgs. As a result, (some of) the leptons and neutrinos are incorporated into the chargino and neutralino sectors. This leads to characteristic decay patterns that can be experimentally tested at the LHC. The corresponding collider phenomenology is largely determined by the new approximately conserved quantum number, which is itself closely tied to the presence of "leptonic R-parity violation". We find rather loose bounds on the first and second generation squarks, arising from a combination of suppressed production rates together with relatively small signal efficiencies of the current searches. Naturalness would indicate that such a framework should be discovered in the near future, perhaps through spectacular signals exhibiting the lepto-quark nature of the third generation squarks. The presence of fully visible decays, in addition to decay chains involving large missing energy (in the form of neutrinos) could give handles to access the details of the spectrum of new particles, if excesses over SM background were to be observed. The scale of neutrino masses is intimately tied to the source of U(1)_R breaking, thus opening a window into the R-breaking sector through neutrino physics. Further theoretical aspects of the model have been presented in a recent companion paper., Comment: 44 pages, 28 figures

A classification of phenomenologically interesting supersymmetric extensions of the Standard-Model with a $U(1)_R$ symmetry is presented. Some of these are consistent with subsets of leptonic or baryonic "R-parity violating" (RPV) operators, thereby providing a natural motivation for them. We then focus on a particular class of models in which the $U(1)_R$ symmetry coincides with lepton number when restricted to the SM sector. In this case, the extension of lepton number to the superpartners is "non-standard", implying, in particular, the existence of the leptonic RPV operators $LLE^c$ and $LQD^c$, and a vacuum structure where one of the left-handed sneutrinos acquires a significant vacuum-expectation-value, while not being constrained by neutrino mass bounds. The model can be naturally consistent with bounds from electroweak precision measurements and flavor-changing processes. It can also easily accommodate the recently measured Higgs mass due to the existence of a scalar triplet that couples to the Higgs with an order one coupling, with only moderate fine-tuning. The phenomenology is rather rich and distinctive, with features such as heavy-but-natural Dirac gauginos, relaxed bounds on squarks, resonant slepton/sneutrino production, lepto-quark signals, as well as an interesting connection to neutrino physics arising from R-breaking. The broad qualitative features are discussed in this paper, with a more detailed phenomenological study carried out in a companion paper Frugiuele et al. (2012)., Comment: 44 pages, 5 figures, references added

Compact spatial dimension at the TeV scale remain an intriguing possibility that is currently being tested at the LHC. We give an introductory review of extra-dimensional models and ideas, from a phenomenological perspective, but emphasizing the appropriate theoretical tools. We emphasize the power and limitations of such constructions, and give a self-contained account of the methods necessary to understand the associated physics. We also review a number of examples that illustrate how extra-dimensional ideas can shed light on open questions in the Standard Model. An introduction to holography is provided. These are the notes of my TASI 2011 Lectures on Extra Dimensions., Comment: 79 pages, 15 figures

We consider the Higgs sector in extensions of the Minimal Supersymmetric Standard Model by higher-dimension operators in the superpotential and the K\"ahler potential, in the context of Higgs searches at the LHC 7 TeV run. Such an effective field theory (EFT) approach, also referred to as BMSSM, allows for a model-independent description that may correspond to the combined effects of additional supersymmetric sectors, such as heavy singlets, triplets or gauge bosons, in which the supersymmetry breaking mass splittings can be treated as a perturbation. We consider the current LHC dataset, based on about $1-2 {\rm fb}^{-1}$ of data to set exclusion limits on a large class of BMSSM models. We also present projections for integrated luminosities of 5 and 15 fb$^{-1}$, assuming that the ATLAS and CMS collaborations will combine their results in each channel. Our study shows that the majority of the parameter space will be probed at the $2\sigma$ level with 15 fb$^{-1}$ of data. A non-observation of a Higgs boson with about 10 fb$^{-1}$ of data will point towards a Higgs SUSY spectrum with intermediate $\tan \beta$ ($\approx$ a few to 10) and a light SM-like Higgs with somewhat enhanced couplings to bottom and tau pairs. We define a number of BMSSM benchmark scenarios and analyze the possible exclusion/discovery channels and the projected required luminosity to probe them. We also discuss the results of the EFT framework for two specific models, one with a singlet superfield and one with SU(2)$_L$ triplets., Comment: 34 pages, 7 figures

It is well known that R-symmetric models dramatically alleviate the SUSY flavor and CP problems. We study particular modifications of existing R-symmetric models which share the solution to the above problems, and have interesting consequences for electroweak baryogenesis and the Dark Matter (DM) content of the universe. In particular, we find that it is naturally possible to have a strongly first-order electroweak phase transition while simultaneously relaxing the tension with EDM experiments. The R-symmetry (and its small breaking) implies that the gauginos (and the neutralino LSP) are pseudo-Dirac fermions, which is relevant for both baryogenesis and DM. The singlet superpartner of the U(1)_Y pseudo-Dirac gaugino plays a prominent role in making the electroweak phase transition strongly first-order. The pseudo-Dirac nature of the LSP allows it to behave similarly to a Dirac particle during freeze-out, but like a Majorana particle for annihilation today and in scattering against nuclei, thus being consistent with current constraints. Assuming a standard cosmology, it is possible to simultaneously have a strongly first-order phase transition conducive to baryogenesis and have the LSP provide the full DM relic abundance, in part of the allowed parameter space. However, other possibilities for DM also exist, which are discussed. It is expected that upcoming direct DM searches as well as neutrino signals from DM annihilation in the Sun will be sensitive to this class of models. Interesting collider and Gravity-wave signals are also briefly discussed., Comment: 50 pages, 10 figures

We study the effect of bulk fermions on electroweak precision observables in a recently proposed model with warped extra dimensions and no custodial symmetry. We find that the top-quark mass, together with the corrections to the Zbb vertex and the one-loop contribution to the T parameter, which is finite, impose important constraints that single out a well defined region of parameter space. New massive vector bosons can be as light as 1.5 TeV and have large couplings to the t_R quark, and suppressed couplings to the t_L, b_L and lighter quarks. We discuss the implications for searches of models with warped extra dimensions at the LHC., Comment: Most relevant one-loop contributions to EWP observables included, physics results partially changed. References added. 29 pages, 14 Figures

Warped scenarios offer an appealing solution to the hierarchy problem. We consider a non-trivial deformation of the basic Randall-Sundrum framework that has a KK-parity symmetry. This leads to a stable particle beyond the Standard Model, that is generically expected to be the first KK-parity odd excitation of the radion field. We consider the viability of the KK-radion as a DM candidate in the context of thermal and non-thermal production in the early universe. In the thermal case, the KK-radion can account for the observed DM density when the radion decay constant is in the natural multi-TeV range. We also explore the effects of coannihilations with the first KK excitation of the RH top, as well as the effects of radion-Higgs mixing, which imply mixing between the KK-radion and a KK-Higgs (both being KK-parity odd). The non-thermal scenario, with a high radion decay constant, can also lead to a viable scenario provided the reheat temperature and the radion decay constant take appropriate values, although the reheat temperature should not be much higher than the TeV scale. Direct detection is found to be feasible if the DM has a small (KK-parity odd) Higgs admixture. Indirect detection via a photon signal from the galactic center is an interesting possibility, while the positron and neutrino fluxes from KK-radion annihilations are expected to be rather small. Colliders can probe characteristic aspects of the DM sector of warped scenarios with KK-parity, such as the degeneracy between the radion and the KK-radion (DM) modes., Comment: 43 pages, 16 figures; added references

Anarchic warped extra dimensional models provide a solution to the hierarchy problem. They can also account for the observed flavor hierarchies, but only at the expense of little hierarchy and CP problems, which naturally require a Kaluza-Klein (KK) scale beyond the LHC reach. We have recently shown that when flavor issues are decoupled, and assumed to be solved by UV physics, the framework's parameter space greatly opens. Given the possibility of a lower KK scale and composite light quarks, this class of flavor triviality models enjoys a rather exceptional phenomenology, which is the focus of this letter. We also revisit the anarchic RS EDM problem, which requires m_{KK} > 8 TeV, and show that it is solved within flavor triviality models. Interestingly, our framework can induce a sizable differential t \bar{t} forward-backward asymmetry, and leads to an excess of massive boosted di-jet events, which may be linked to the recent findings of the CDF collaboration. This feature may be observed by looking at the corresponding planar flow distribution, which is presented here. Finally we point out that the celebrated standard model preference towards a light Higgs is significantly reduced within our framework., Comment: 6 pages, 3 figures. Updated the EDM bound on the anarchic scenario; extended discussion on the KK gluon's width, discovery potential and resulting dijet signal; matches published version

We consider a 5D warped scenario with a KK-parity symmetry, where the non-trivial warping arises from the dynamics that stabilizes the size of the extra dimension. Generically, the lightest Kaluza-Klein (KK) particle is the first excitation of the radion field, while the next-to-lightest Kaluza-Klein particle is either the first excitation of the (RH) top quark or the first KK-parity odd Higgs. All these masses are expected to be of order the electroweak scale. We present simple analytical expressions for the masses and wavefunctions of the lowest lying KK modes, and derive the Feynman rules necessary for phenomenological applications. The framework allows to interpolate between a strongly warped scenario a la Randall-Sundrum (RS), and a weakly warped scenario that shares properties of both RS and Universal Extra Dimensions models., Comment: 41 pages, 13 figures. Minor comments added. Published version

In warped models that solve the hierarchy problem, there is generally no dynamical relation between the size of the fifth dimension and the scale of electroweak symmetry breaking (EWSB). The establishment of such a relation, without fine-tuning, requires that Casimir contributions to the radion potential not exceed the energy density associated with EWSB. Here, we examine the use of supersymmetry for controlling the Casimir energy density and making quantum contributions calculable. We compute the effects of supersymmetry breaking at the UV and IR boundaries of warped backgrounds, in the presence of brane localized kinetic terms. Various limits of supersymmetry breaking are examined. We find that when supersymmetry is broken on the UV brane, vacuum contributions to the radion potential can be controlled (as likely necessary for EWSB to govern the radion potential) via small soft masses as well as a "double volume suppression." Our formalism can also provide a setup for radion stabilization by bulk fields, when supersymmetry is broken on both the UV and the IR branes., Comment: Discussion of brane tension effects substantially revised. Main physical conclusions unchanged. Latex, 20 pages

A warped extra-dimensional model, where the Standard Model Yukawa hierarchy is set by UV physics, is shown to have a sweet spot of parameters with improved experimental visibility and possibly naturalness. Upon marginalizing over all the model parameters, a Kaluza-Klein scale of 2.1 TeV can be obtained at 2 sigma (95.4 CL) without conflicting with electroweak precision measurements. Fitting all relevant parameters simultaneously can relax this bound to 1.7 TeV. In this bulk version of the Rattazzi-Zaffaroni shining model, flavor violation is also highly suppressed, yielding a bound of 2.4 TeV. Non-trivial flavor physics at the LHC in the form of flavor gauge bosons is predicted. The model is also characterized by a depletion of the third generation couplings -- as predicted by the general minimal flavor violation framework -- which can be tested via flavor precision measurements. In particular, sizable CP violation in Delta B=2 transitions can be obtained, and there is a natural region where Bs mixing is predicted to be larger than Bd mixing, as favored by recent Tevatron data. Unlike other proposals, the new contributions are not linked to Higgs or any scalar exchange processes., Comment: 44 pages, 6 figures; v2: major revision: author added; title changed; extended statistical analysis; added discussion about fine-tuning and flavor appendix; results slightly changed. v3: minor corrections and clarifications; reference added; matches published version

We consider extensions of the Minimal Supersymmetric Standard Model (MSSM) where the extra degrees of freedom interact weakly with the Higgs sector. These models allow to relax the tension between the lower bound on the lightest CP even Higgs mass from direct LEP searches and the theoretical upper bound of the MSSM. We study the beyond MSSM (BMSSM) effects via an effective field-theory approach, assuming that the MSSM is valid up to a heavy physics scale M. We compute the masses, couplings and branching fractions of the Higgs sector, including all the relevant corrections up to order 1/M^2. We find that the collider phenomenology can be greatly different with respect to both the SM and the MSSM., Comment: Contribution to the XVIII International Workshop on Deep-Inelastic Scattering and Related Subjects, April 19 -23, 2010, Florence, Italy. 5 pages, 2 figures

We study extensions of the Minimal Supersymmetric Standard Model (MSSM) with new degrees of freedom that couple sizably to the MSSM Higgs sector and lie in the TeV range. After integrating out the physics at the TeV scale, the resulting Higgs spectrum can significantly differ from typical supersymmetric scenarios, thereby providing a window Beyond the MSSM (BMSSM). Taking into account current LEP and Tevatron constraints, we perform an in-depth analysis of the Higgs collider phenomenology and explore distinctive characteristics of our scenario with respect to both the Standard Model and the MSSM. We propose benchmark scenarios to illustrate specific features of BMSSM Higgs searches at the Tevatron and the LHC., Comment: 18 pages, 9 figures; added parameters for each benchmark point, typos corrected, final version published by Phys. Rev. D

The Large Hadron Collider presents an unprecedented opportunity to probe the realm of new physics in the TeV region and shed light on some of the core unresolved issues of particle physics. These include the nature of electroweak symmetry breaking, the origin of mass, the possible constituent of cold dark matter, new sources of CP violation needed to explain the baryon excess in the universe, the possible existence of extra gauge groups and extra matter, and importantly the path Nature chooses to resolve the hierarchy problem - is it supersymmetry or extra dimensions. Many models of new physics beyond the standard model contain a hidden sector which can be probed at the LHC. Additionally, the LHC will be a top factory and accurate measurements of the properties of the top and its rare decays will provide a window to new physics. Further, the LHC could shed light on the origin of neutralino masses if the new physics associated with their generation lies in the TeV region. Finally, the LHC is also a laboratory to test the hypothesis of TeV scale strings and D-brane models. An overview of these possibilities is presented in the spirit that it will serve as a companion to the Technical Design Reports (TDRs) by the particle detector groups ATLAS and CMS to facilitate the test of the new theoretical ideas at the LHC. Which of these ideas stands the test of the LHC data will govern the course of particle physics in the subsequent decades., Comment: Summary document for international workshop "Beyond the Standard Model at the LHC" (Pre-SUSY09), Northeastern University, Boston, June 2-4, 2009