Category Archives: Physics

Ready for a smashing success

June 3, 2015 Leah Burrows Leave a comment

After two-years of upgrades and repairs, the Large Hadron Collider is back in the particle smashing business — this time at double the energy of its first run. Today, researchers at CERN began recording data from the highest-energy particle collisions ever achieved on Earth, and began a new set of experiments that will shed light on a new realm of physics.

I spoke with professor Gabriella Sciolla about the restart and the frontier of physics.

What are the biggest discoveries physicists hope to make in the coming year with this new, improved experiment?

The big goal is to search for what we call “New Physics,” meaning new elementary particles and new interactions that extend our understanding. We can summarize the search for New Physics in three categories: the search for new elementary particles; the search for dark matter; and the measurement of the Higgs boson’s properties.

New elementary particles are predicted by exotic theories, such as supersymmetry or extra dimensions, but have never been observed.

Dark matter particles, which make up 85 percent of the mass of the universe and have never been observed in the lab, can be produced in high-energy proton-proton collisions at the LHC. Seeing them for the first time would be a revolutionary achievement.

Watch this video about the Sciolla Lab’s hunt for dark matter

New interactions and new particles will affect the behavior of the Higgs boson. For example, the Higgs will interact with other particles in a way that is different from what the current theory predicts.

What are you most excited about?

Difficult choice! These three avenues are all very promising and may all lead to a paradigm shift in physics. However, choices need to be made since we cannot work on each and every topic.

At the very beginning of Run 2, my group will focus on two topics: extra dimensions and dark matter. Theories of extra dimensions predict a new particle, known as Graviton, that decays into two energetic elementary particles called muons. Given our know-how in muon reconstruction, it is natural for my group to lead these searches.

This experiment costs an awful lot of money. What do you tell people who question its value?

It’s hard to put a price tag on knowledge. This experiment gives us a chance to understand how the universe works at its most fundamental level. The technological applications we develop in pursuit of scientific answers are important. But understanding the basic science will benefit humanity in the long term.

The LHC experiments are international projects, so we share the costs. The ATLAS experiment, for example, was built by a collaboration of 38 countries on four continents.

What will you be thinking when the experiment officially restarts?

It will certainly be a historic moment. These collisions could change the way we think about particle physics. Since I am responsible for the reconstruction and calibration of muons in the ATLAS experiment, I will be totally absorbed in delivering the best quality muons to the collaboration. Muons are crucial ingredients for many searches for New Physics.

If the accelerator works as expected, we need only a few months of data to publish our first results. We can’t wait!

Physics, Research

Birds, bees and the nature of space

April 24, 2015 Leah Burrows Leave a comment

Ever wonder what theoretical physicists actually do? In honor of the 100th anniversary of Albert Einstein’s theory of general relativity, ReAction is sitting down with theoretical physicists at Brandeis to find out.

Theoretical physics is a lot like sex, Nobelist Richard Feynman once quipped. “Sure, it may give some practical results, but that’s not why we do it.”

The prevailing stereotype outside — and inside — the sciences is that theoretical physicists have their gaze firmly fixed on their navels and play in a sandbox of their own creation.

It’s time to throw that stereotype out the window (and note how it falls to Earth with constant acceleration. Thanks, theoretical physics!)

Sure, theoretical physics can get weird, and some theories are pretty far out, but inquiry is always driven by a hunger to understand the universe fundamentally.

Consider Brandeis’ High Energy and Gravitational Theory Group.

These physicists research bizarre principles like holography , which postulates that all the information in the universe is stored on a two-dimensional surface, and we are mere projections of that information. And then there’s quantum entanglement, which even Einstein called “spooky.”

But at the core of the group’s research is a simple question: What is space?

Einstein described the way space is connected to time and how it interacts with mass. But he never theorized what space is, how it’s formed or what it’s made of.

Einstein's general relativity reimagined gravity not as force, as Newton described it, but as space curved by matter, through which matter travels. — General relativity reimagined gravity not as force, as Newton described it, but as space curved by matter. Courtesy/NASA

“Since Einstein, our questions have gotten bigger and deeper,” says Matthew Headrick, assistant professor of physics. “We want to figure out the nature of space.”

The answer lies somewhere between two pillars of modern theoretical physics — general relativity ( GR, which describes gravity) and quantum field theory ( QFT, which describes, among other things, particle physics). These fundamental theories describe two very different aspects of our universe and are written in different mathematical languages.

Watch this video for an overview of QFT and GR

“Shockingly, in certain cases, theorists have discovered that these two very different theories are actually secretly the same,” Headrick says. “Between GR and QFT, there is some kind of one-to-one map. We know some of the shared points but we’re still in the dark about many others.”

This one-to-one map is holography and it represents GR, which lives in ordinary three-dimensional space, by a QFT living on a two-dimensional surface — just like a hologram.

Essentially, Headrick and other theoretical physicists are building a Rosetta Stone —a bilingual dictionary of sorts — using holography, general relativity and quantum field theory. This translational tool will expose how GR and QFT are connected to each other and how to build a new language that obeys the properties of both GR and QFT.

Word by word, Headrick and his colleagues are testing and building a framework of conjectures.

“If you have confidence that a conjecture obeys the properties it needs to obey, you can enter it into the dictionary,” Headrick says. “Each small entry tells us something more about space.”

One conjecture Brandeis theorists pioneered has to do with the relationship between the geometry of space and the quantum information it contains.

Mathematically, certain areas in curved space contain minimal surfaces — a surface that minimizes its area. Dip a wand into soapy water and the soap film will stretch perfectly flat across the shape of the wand. This is a minimal surface.

“If the area of that soap film is expressed in fundamental units, it tells us about the quantum entanglement in the QFT,” says Headrick.

In other words, Headrick and his colleagues use the mathematical language of general relativity — geometry — to extrapolate a quantum property. That calculation, in turn, provides new information about how the two languages are interconnected.

That idea also provides a clue to the nature of space.

“It suggests that, fundamentally, the space that we live in and take for granted is stitched together out of quantum entanglement,” Headrick says.

Watch this video for an overview of entanglement

The next step is to figure out why.

The answers to these and other questions will, with any luck, give researchers the words and syntax to compose a theory of gravity in the language of quantum mechanics. It’s the Holy Grail of modern theoretical physics: a theory of quantum gravity.

But what does this have to do with reality? Richard Feynman may not have cared about the practical results of theoretical physics, but some do.

Be patient, Headrick says.

It took Einstein 10 years to develop general relativity, and it took physicists another 40 years to understand the black holes it predicted. Now, 100 years after the theory’s publication, relativity is ubiquitous in our daily lives. Without an understanding of it, for example, we wouldn’t have GPS.

But more important than the inventions a theory spurs, is the knowledge a theory advances, Headrick says.

“Einstein, Feynman and others profoundly changed our understanding of nature,” he says.

And that’s why theoretical physicists do it.

Special thanks to Cesar Agón for helping in the development of this story.

Physics, We Are Brandeis Science

We Are Brandeis Science: Hannah Herde

April 6, 2015 Leah Burrows Leave a comment

There is no rule that says scientists have to look or act a certain way. Scientists can be funny and outgoing, athletic and artistic. They come from all different backgrounds and have all different interests. Who are the people behind the groundbreaking research at Brandeis University? We Are Brandeis Science aims to find out. This on-going series is inspired by This is What a Scientist Looks Like.

This post was written by physics PhD candidate Hannah Herde.

A mind-blowing mystery

Where are you from?

That’s a complicated question. I was born in Washington, D.C. but lived in New Canaan, Conn., for most of my life. My family moved to London during my middle school years, where Britain’s dedication to science education certainly helped me to develop my passion.

What do you research?

Herde in front of the Globe of Science at CERN

I work with physics professor Gabriella Sciolla on the search for dark matter, one of the greatest mysteries of the universe. As it turns out, dark matter accounts for 85 percent of the mass of the universe — which blows my mind. I would very much like to find out what most of the universe is made of, and how these materials interact with the matter out of which you and I, the stars, and everything else we perceive, is made.

As a kid, what did you want to be when you grew up?

When I was 8 years old, I wanted to be an oceanographer — I wanted more than anything else to probe the fathoms of the sea. That was my dream for nearly a decade and during high school, I worked more than 300 hours at The Maritime Aquarium in Norwalk, Conn. Through my experience there, I learned that I wanted to understand more than just what is out there — I wanted to understand how everything works and why it came to be that way. As I continued my education, I came to feel that those questions were best answered through physics.

What got you into science?

Dirt. Good old-fashioned digging in the dirt. I was very fortunate growing up — my parents made sure that my three siblings and I always had a yard in which to play. Pill bugs, rocks, flowers, frogs — just about anything I could find in the yard rapidly transformed into an experiment.

What’s the coolest place you’ve ever been?

CERN’s Large Hadron Collider, 150 meters underground at the ATLAS detector. It is enormous!

Physics, Research

Enter Sandwoman

Video March 23, 2015 Leah Burrows Leave a comment

Let’s put winter behind us — it’s time to think about sand.

Physicists think about sand a lot because they don’t really understand how it works. How can sand — and other granular materials such as grains or rocks — behave both like a liquid that flows through fingers and a solid that forms dunes?

Physicists have a theoretical framework to predict how microscope objects like molecules flow and freeze but lack the fundamental concepts to describe how assemblies of macroscopic objects behave similarly.

Last year, Bulbul Chakraborty, the Enid and Nate Ancell Professor of Physics received a three-year, $1 million grant from the W.M. Keck Foundation to develop the first predictive theoretical framework to characterize the collective behavior of a large number of macroscopic objects.

BulbulSand — This theoretical representation of experimental data (Behringer Lab.) provides a quantitative tool for identifying the fluid to solid transition in a granular solid. The fluctuations in the net show the change in strength of the solid. Credit: Sumantra Sarkar, Brandeis University

She and her team are developing quantitative tools for identifying the fluid to solid transition in granular solids in order to build a theoretical framework to describe assemblies of macroscopic objects.

Here is a peak inside her lab.

Physics, Research

Science friction: Unlocking this basic force may lead to futuristic technologies

March 4, 2015 Leah Burrows Leave a comment

Here’s the rub with friction — scientists don’t really know how it works. Sure, humans have been harnessing the power of friction since rubbing two sticks together to build the first fire, but the physics of friction remains largely in the dark.

Ancient Egyptians used friction — Ancient Egyptians understood friction well enough to know that heavy objects moved easier across wet sand than dry sand, as can be seen in this picture.

In a new paper in Nature Materials, Brandeis University professor Zvonimir Dogic and his lab explored friction at the microscopic level. They discovered that the frictional force is much stronger than previously thought. The discovery is an important step toward understanding the physics of the cellular and molecular world and designing the next generation of microscopic and nanotechnologies.

The research was conducted as part of the Brandeis University Materials Research Science and Engineering Center.

Dogic and his team focused on the frictional forces of actin filaments, essential cellular building blocks responsible for many biological functions including muscle contraction, cell movement and cell division. All of these processes require filaments to move and slide against one another, generating friction.

Actin filament experiment — A schematic of the experimental set-up. Actin filaments attached to gelsolin-coated beads are assembled into anti-parallel bundles using optical traps. Bead 2 is pulled at a constant velocity while simultaneously measuring the force exerted on bead.

Scientists assumed that the frictional forces of these movements were minimal, acting more like weaker hydrodynamic friction — like pulling an object through water — than the larger solid friction — pushing an object across a desk.

But Dogic and his team observed the opposite. They developed a new technique to measure friction, and when they dragged two actin filaments against each other, they observed frictional forces nearly 1,000 times greater than expected — closer to solid friction than hydrodynamic friction.

This is due, in part, to interfilament interaction. Imagine filaments as two beaded strings, one on top of the other, pulled in opposite directions. As the strings move, the beads must go up and over their counterparts on the opposite string, generating even more friction. By observing this interfilament interaction, Dogic and his team were able to measure the frictional forces and tune them, altering the forces to include more or less friction.

“Before this research, we didn’t have a good way of controlling or understanding friction,” Dogic says. “We still have a lot more to understand but now, one of our oldest sciences is becoming less opaque.”

The paper was coauthored by Brandeis scientists Andrew Ward, Fiodar Hilitski, Walter Schwenger and David Welch; A. W. C. Lau of Florida Atlantic University; Vincenzo Vitelli of the University of Leiden, and L. Mahadevan of Harvard University.

This research was funded by the National Science Foundation.

Astronomy, Physics, Undergraduate

An Overwhelming Sense of Discovery

January 21, 2015 Leah Burrows Leave a comment

Jose Vargas ’15 is a time traveler.

As an undergraduate researcher in professor John Wardle’s lab, Vargas studies quasars, the brightest and most remote objects in the universe, clocking in at 10 to 12 billion light years away, meaning Vargas is looking 10 to 12 billion years in the past.

Quasars form when supermassive black holes — billions of times the mass of the Sun — feed on nearby material. The matter forms an accretion disk around the black hole, heating up to millions of degrees and blasting out radiation and powerful jets of particles, traveling at nearly light speed — like the universe’s largest particle colliders.

Astrophysicists believe that quasars may be an important step in the birth of galaxies.

We asked Vargas to describe what it’s like to see into the past. Here is what he said:

Faculty, Physics, Research

The hunt for dark matter (and other fun physics in 2015)

Video December 15, 2014 Leah Burrows Leave a comment

There may not be an equation to prove it — but 2015 promises to be a big year for Brandeis physics.

In 2015, the Large Hadron Collider at CERN — the world’s largest science experiment — will reboot after two years of upgrades, with double the energy of its first run. The Brandeis High Energy Physics Group will be in the thick of it, exploring the newly discovered Higgs boson and hunting for supersymmetry, dark matter and extra dimensions.

With its National Science Foundation Grant renewed for six years at $12 million, The Brandeis Bioinspired Soft Materials Research Science and Engineering Center (MRSEC) will enter a new phase in 2015. Led by physicist Seth Fraden, the interdisciplinary group will continue its groundbreaking research into active biological matter and membranes materials, paving the way for soft robotics, novel drug delivery systems and artificial cells.

Over the next year, the Brandeis Astrophysics Group will continue its exploration of the cosmos, peering deep into the cores of galaxies and quasars, while Brandeis theorists continue to unravel the mysteries of quantum entanglement and gravity.

Expect new ideas and directions in undergraduate education as well, says professor Jané Kondev, physics department chair. In 2014, Kondev received a $1 million grant from The Howard Hughes Medical Institute to bolster interdisciplinary undergraduate research at Brandeis.

In 2015, physics professor Zvonimir Dogic and biology professor Melissa Kosinski-Colllins will begin collaborating on a new first-year lab course for premeds and life-science students, focusing on the physics of living systems.

Whether you’re interested in dark matter or active matter, 2015 promises to be an exciting year. Stay tuned!

Astronomy, Physics, Undergraduate

Wandering the stars with the Brandeis Astronomy Club

November 10, 2014 Leah Burrows Leave a comment

The Brandeis Astronomy club, led by Isaac Steinberg, meets several times a month to observe and photograph the cosmos. Here are a few of their snapshots:

Jupiter has the shortest day of all the planets in our solar system. It turns on its axis once every 9 hours and 55 minutes, spinning so quickly that the planet is slightly flat, giving it an oblate shape.

The moon is rotating in synchrony with the earth, known as tidal locking. As a result we can only see the near side of the moon from Earth.

The Andromeda Galaxy is the nearest spiral galaxy to the Milky Way, which is also a spiral galaxy. It has an approximate trillion stars to our puny 300 billion. This image was composed of 8 long exposure photos, which were then merged to pull out detail and remove noise.

The Albireo star system (center) is in the constellation Cygnus. The larger of the double star is a binary star system composed of two stars that orbit each other. The larger star appears yellow and the smaller one blue when resolved with a telescope.

Saturn, the sixth planet from the sun and the second largest in the solar system, is mostly helium.

Vega is the fifth brightest star in the night sky and 25 light years away. It is found in the constellation Lyra.

Faculty, Physics, Research

Dogic Lab gets Science cover

Aside September 9, 2014 Leah Burrows Leave a comment

On Sept. 5, the Dogic lab’s active matter research was featured on the cover of the journal Science. Dogic, with a team from Technical University of Munich (TU Munich), Leiden University in the Netherlands, and Syracuse University, created a Frankenstein-like synthetic sac, stitched together from different kinds of biomolecules, that can move and change shape on its own. It’s called an active nematic vesicle and it could be the first step towards building artificial cells.

Faculty, Physics, Research

Making the Case for Cool Science

September 9, 2014 Leah Burrows Leave a comment

In 1888, an Austrian botanist dissected a carrot and today, we have LCD TVs. That’s the thing about science, you never know where it will lead.

That botanist was Friedrich Reinitzer, and he observed cholesterol extracted from a carrot that behaved both like a liquid and a solid. It was the first observation of a liquid crystal. Over the next century, it spawned a new field of research and countless technologies.

Would Reinitzer’s research be funded today?

With funding down and competition up, researchers have to fight for every dollar. Even fundamental researchers — the scientists who explore the basic building blocks of life and matter — are often asked to predict how their research could be applied.

At Brandeis, researchers build the foundations for curing disease, developing clean energy and understanding the cosmos. The research goal may be identifying how a particular protein operates in the disease process, or which chemicals won’t act like greenhouse gases in the atmosphere. But we also celebrate research that explores an unknown frontier without knowing where it will lead.

Physicists Zvonimir Dogic and Michael Hagan are doing just that.

Recently, their research into two-dimensional physics was featured in Nature, one of the most respected journals in science. The paper was also authored by Brandeis University graduate students Prerna Sharma and Andrew Ward. Knowing just how their research will be applied is decades down the road. But that doesn’t diminish the cool factor; indeed maybe it heightens it.

In the three-dimensional world, oil and water separate when combined. The smaller droplets of oil merge with larger ones, eventually forming one continuous layer that floats on water.

It’s a basic principle in physics.

But in the two-dimensional world, things work very differently.

Take our cell membranes, a two-dimensional liquid world. Liquid lipid “rafts” float on the surface of membranes, carrying proteins and regulating transport in and out of the cell.

If the lipid rafts behaved like liquid in the three-dimensional world, the individual rafts would coalesce into one larger raft.

But, as the researchers observed, the 2-D world has its own operating system.

To get an inside peek at this microscopic world, Dogic and Hagan needed to scale up, big time. They used long rod-like viruses to create a colloidal membrane — a membrane made up of thousands of smaller particles — like our cell membranes except much, much larger.

To build the lipid rafts, they used shorter rod-like viruses.

When the team put the shorter and longer viruses together, something unexpected happened: instead of separating like oil and water, the short rods self-assembled into smaller droplets of equal size and shape.

And they held that size and shape. Even when the sample started out with different sized droplets, they all equalized.

Even when the team split a droplet, it returned to its original size a few hours later.

Dogic and Hagan discovered droplets don’t coalesce because they actively repel each other, like magnets flipped on one side. A droplet’s chirality — the way its component rods twist in space — creates a distortion in the membrane, which its fellow droplets want to avoid. The effect is long-range, with the droplets avoiding each other as far as 10 diameters away.

The droplets constantly exchange and rearrange their rods to maintain the same size.

In the 3-D world this just doesn’t happen, but our rules don’t apply to the 2-D world.

Dogic and Hagan also discovered that by tweaking the parameters of the droplets — their chirality, for example — they can assemble into different shapes, like long, polymer-like strings or horseshoes.

So what does this all mean?

It means we’re just beginning to lift the curtain on the two-dimensional world. Sure, Dogic and Hagan can speculate about applications like self-healing fabrics or new drug delivery systems, but right now, it’s just cool science. No, it’s fundamental science. And that’s cool.

Discovery in action at Brandeis University